Suchergebnisse

This post is from a set of comments I gave at the NBER Asset Pricing conference in early November at Stanford.  Conference agenda here. My full slides here. There was video, but sadly I took too long to write this post and the NBER took down the conference video. I was asked to comment on "Downward Nominal Rigidities and Bond Premia" by François Gourio  and Phuong Ngo. It's a very nice clean paper, so all I could think to do as discussant is praise it, then move on to bigger issues. These are really comments about whole literatures, not about one paper. One can admire the play but complain about the game. The paper implements a version of Bob Lucas' 1973 "International evidence" observation. Prices are less sticky in high inflation countries. The Phillips curve more vertical. Output is less affected by inflation. The Calvo fairy visits every night in Argentina. To Lucas, high inflation comes with variable inflation, so people understand that price changes are mostly aggregate not relative prices, and ignore them. Gourio and Ngo use a new-Keynesian model with downwardly sticky prices and wages to express the idea.  When inflation is low, we're more often in the more-sticky regime. They use this idea in a model of bond risk premia. Times of low inflation lead to more correlation of inflation and output, and so a different correlation of nominal bond returns with the discount factor, and a different term premium. I made two points, first about bond premiums and second about new-Keynesian models. Only the latter for this post. This paper, like hundreds before it, adds a few ingredients on top of a standard textbook new-Keynesian model. But that textbook model has deep structural problems. There are known ways to fix the problems. Yet we continually build on the standard model, rather than incorporate known ways or find new ways to fix its underlying problems. Problem 1: The sign is "wrong" or at least unconventional.The basic sign is wrong -- or at least counter to the standard belief of all policy makers. In the model, higher interest rates cause inflation to jump down immediately, and then rise over time. Everyone at the Fed uniformly believes that higher interest rates cause inflation to go nowhere immediately, and then gently decline over time, with "long and variable lags." Larry Ball pointed this out 30 years ago. The behavior comes straight from the forward-looking Phillips curve. Lower output goes with lower inflation, relative to future inflation. I.e. inflation rising over time. To be clear, maybe the model is right and the beliefs are wrong. It's amazing that so much modeling and empirical work has gone in to massaging theory and data to conform to Milton Friedman's 1968 proclamation of how monetary policy works. The "long and variable lags" in particular are a trouble to modern economics. If you know prices are going up tomorrow, you raise prices today. But that's for another day. This model does not behave the way most people think the economy behaves, so if you're going to use it, at least that needs a major asterisk.  Well, we know how to fix this. You can see that sneaking lagged inflation into the Phillips curve is going to be a big part of that.  Christiano Eichenbaum and Evans, 20  years ago, produced a widely cited model that "fixes" this problem. It has a lot of ingredients. Most of all, it assumes that wages and prices are indexed. Firms and workers that don't get tapped by the Calvo fairy to change their price or wage nonetheless raise by observed inflation. This gives a Phillips curve with lagged inflation. Moreover, in preferences, investment, and this Phillips curve, CEE modify the model to put growth rates in place of levels. (More review in a three part series on new-Keynesian models here.) The result: If the funds rate goes down (right panel) unexpectedly, inflation goes down just a bit but then turns around and goes up a year later. (Several other authors get to the same place by abandoning rational expectations. But that has its own problems, and it's going to be hard to incorporate asset pricing that way. Much more in Expectations and the Neutrality of Interest Rates) Great. But notice that neither Gourio and Pho nor pretty much anyone else builds on this model. We cite it, but don't use it. Instead, 20 more years of NK theorizing studies different extensions of the basic model, that don't solve the central conundrum. Problem 2: Fed induced explosionsThe standard new-Keynesian model says that if the Fed holds interest rates constant, inflation is stable -- will go away on its own -- but indeterminate. There are multiple equilibria. The standard new-Keynesian model thus assumes that the Fed deliberately destabilizes the economy. If inflation comes out more than the Fed wishes, the Fed will lead the economy to hyperinflation or hyper deflation. Under that threat, people jump to the inflation that the Fed wishes to see. But the Fed does no such thing.  Central bankers resolutely state that their job is to stabilize the economy, to bring inflation back from wherever it might go. Despite thousands of papers with new-Keynesian equations written at central banks, if anyone were ever to honestly describe those equations in the introduction, "we assume that the central bank is committed to respond to inflation by hyperinflation or deflation in order to select from multiple equilibria" they would be laughed out of a job. This has been clear, I think, since 2000 or so. I figured it out by reading Bob King's "Language and Limits." My  "Determinacy and Identification" in the JPE 2011 was all about this. We've also known at least one way to fix it, as shown: fiscal theory. OK, I'm a broken record on this topic. Instead, we go on with the same model and its underlying widely counterfactual assumption about policy. Problem 3: The fit is terribleA model consists of a set of equations, with the thing you want to determine (say, inflation) on the left, the economic causes described by the model on the right, plus "shocks," which are things your model can't capture. In the explanation part, there are parameters (\(\sigma, \ \beta, \ \kappa, \ \phi\)), that control how much the things on the right affect the things on the left. The fit of new-Keynesian models is usually terrible. In accounting for economic variables (\(x_t,\) \(\pi_t, \) \(i_t \) here), the error terms (\(\varepsilon\)) are much larger than the model's economic mechanisms (the \(x,\) \(\pi\) on the right hand side). Forecasts -- predicting  \(\pi\), \(x\) ahead of time -- is worse. For example, where did inflation come from and why did it go away? Expected inflation hasn't moved much, and the economy just plugged along. Most of the rise and fall of inflation came from inflation shocks.  Related, the fit of the models is about the same amount of terrible for different values of the parameters. That means the parameters are "poorly identified" if identified at all. That means that the mechanisms of the model -- say, how much higher interest rates lower output, and then how much lower output affects inflation -- are weak, and poorly understood. In part this isn't often noticed because we got out of the habit of evaluating models by fit in the 1980s. Most models are evaluated, as I showed above for CEE by matching select "identified" impulse response functions. But as those response functions also explain small variances of output and inflation, it's possible to match response functions well, yet still fit the data badly, i.e. fit the data only by adding big shocks to every equation. I don't know of good fixes here. Old fashioned ISLM models had similar problems (See Sims 1980). But it is a fact that we just ignore and go on. The Phillips curve is a central problem, which has only gotten worse lately. Unemployment was high and declining throughout the 2010s, with stable inflation. Inflation came with high unemployment in 2021. And inflation fell with no high real interest rates, no unemployment, and strong growth in 2022-2023. But what will replace it? So where are we?Macro is surprisingly un-cumulative. We start with a textbook model. People find some shortcomings and suggest a fix. But rather than incorporate that fix, the next paper adds a different fix to the same textbook  model. One would think we would follow the path on the right. We don't. We follow the path on the left. This is common in economics. The real business cycle literature followed much the same path. After the King Plosser Rebelo stochastic growth model became the standard, people spent a decade with one extension after another, each well motivated to fix a stylized fact. But by and large the next paper didn't build on the last one, but instead offered a new variation on the KPR model. Posteriors follow priors according to Bayes' rule, of course. So another way of putting the observation, people seem to put a pretty high prior on the original model, but don't trust the variations at all. I sin too. In Fiscal Theory of the Price Level  I married fiscal theory with the new-Keynsian IS and Phillips curve, exactly as above, despite problems #1 and #3. Well, it makes a lot of sense to change one ingredient at a time to see how a new theory works. I'm unhappy with the result, but I haven't been able to move on to a new and better textbook model, which is what has occasioned several of these related posts.  Wę need a digestion. Which of the new ingredients are reliable, robust, and belong as part of the new "textbook" model? That's not easy. Reliable and robust is very hard to find, and to persuade people. There are so many to choose from -- CEE's smorgasbord, capital, financial frictions, heterogeneous agents, different expectation formation stories, different pricing frictions,  and so on. What's the minimal easy set of these to use? Part of the trouble lies in how publishing works. It's nearly impossible to publish a paper that removes old ingredients, that digests the model down to a new textbook version. The rewards are to publishing papers that add new ingredients. Even if, like CEE, everyone cites them but doesn't use them. I've asked many economists why they build on a model with so many known problems, and why they don't include known fixes. (Not just fiscal theory!) The answer is usually, yes, I know about all these problems, but nobody will bother me about them since every other paper makes the same assumptions, and I need to get papers published.     I went on a bit of a tear here as I referee lots of great papers like this one. Every part of the paper is great, except it builds on a model with big flaws we've known about for 30 years. It feels unfair to complain about the underlying model, since the journal has published and will publish a hundred other papers. But at what point can we, collectively, scream "Stop!" The new-Keynesian model has been the standard model for an astonishing 30 years. None of ISLM, monetarism, rational expectations, or real business cycles lasted that long.  It's even more amazing that it is so unchanged in all this time. It is definitely time for a better textbook version of the model! Maybe this is a plea for Woodford, Gali or one of the other NK textbook authors, which much better command of all the variations than I have, to bless us a new textbook model. Or, perhaps it's time for something totally new. That's not fiscal theory per se. Fiscal theory is an ingredient, not a model.  You can marry it to new-Keynesian models, as I, Leeper, Sims, and others have done. But you can also marry it to old ISLM or anything else you want. Given the above, maybe there isn't an existing modification but a new start. I don't  know what that is. (My comments also have some similar comments about term premiums and how to think about them, but this post is long enough.) Update:Twitter correspondents Stéphane Surprenant and Tom Holden point me to The Transmission of Monetary Policy Shocks by Silvia Miranda-Agrippino Giovanni Ricco in the AEJ Macro, and Inflation, output and markup dynamics with purely forward-looking wage and price setters by Louis Phaneuf, Eric Sims, and Jean Gardy Victor in the European Economic Review. The former is a VAR with high frequency measurement of the monetary policy shock. And.. Source: Miranda-Agrippino and RiccoThe price level as well as the inflation rate can jump down immediately when the interest rate rises! (I think the graph plots the level of CPI, not growth rate.) That's even stronger than the baseline model in which the price level, being sticky, does not move, but the inflation rate jumps on the interest rate rise. The latter is a nice theoretical paper. It adds a lot of the CEE assumptions.  I overstated a great deal that others have not used these ingredients.  They are used in these "medium scale" models, just not in "textbook" models. However, it gets rid of indexed prices and wages with purely forward looking Phillips curves. It adds intermediate goods however. This makes prices changes work through the network of suppliers adding interesting dynamics, which has always struck me as a very important ingredient. And...Source: Phaneuf, Sims ,and VictorThe main estimate is the dark line. Here you see a model with the conventional response: inflation does not move on impact, and increases some time after the interest rate rise.  So, we can switch places! Estimates can replicate the conventional model, with an instant inflation response. Models can replicate the conventional estimates, with a slow inflation response. This one is much prettier than CEEs. 

We're reasonably sure this isn't what they meant to do but there we are. One of the joys about economics is that it has to add up. If this is happening here in the economy then that over there must also be. One can then check and see whether the first is indeed going on by looking for that second that is, or is not. Equally, if we declare that this one thing is true when moving this way then it will also be true when running the other.The IPPR wants to tell us that government borrowing to "invest" (the "" is because it's extraordinarily rare that govt does invest, rather than spend to pleasure voting blocs) doesn't have much effect upon things. Don't take my word for it. The International Monetary Fund's chief economist last year wrote: "The magnitudes of the effects [of fiscal tightening on inflation] appear to be small." Economists from the Bank of England and the Bank of International Settlements also find very limited impact of extra government borrowing on inflation, if any at all. Recent experience also illustrates this: the US government had a significantly higher deficit than the UK last year, and yet it saw inflation fall to a lower level than we did.That is, borrowing to spend is not very stimulatory. Hmm. But then that means that borrowing to spend is not very stimulatory. Or at very least there has to be some 'splainin' done as to why it is when it isn't. But if borrowing to spend isn't stimulatory then we've just disproven one of the major planks of Keynesian economic management. That fiscal policy, the widening out of the deficit, solves recessions. For if we say that fiscal policy isn't stimulatory then that is what we're saying, fiscal policy isn't stimulatory.Which is interesting, no? And will IPPR recall this next recession and not tell us that government should borrow more to spend? No, we don't think so either.

From March 2020: I really hope the fiscal stimulus debate doesn't gain momentum. Not only is it premature…..but I don't have the writing bandwidth to remind everyone how Keynesian stimulus is an outdated theory (the multiplier is close to zero) with a terrible historical track record. That's from a Twitter post by Mr. Brian Riedl. […]

by Andreas Hoffmann These days many commentators suggest that in Turkey a recession is on the way. But nominal GDP has continued to grow along trend. Market monetarists, Keynesians, and some Hayekians believe that NGDP targeting could have prevented major recessions in the U.S. and in Europe following the 2008 financial crisis. To this end, … Continue reading Turkey’s Nominal GDP: No Recession?

After the 2008/9 recession the coalition government famously adopted a set of contractionary fiscal policies with the aim to reduce national debt. Elements of this austerity programme included significant cuts to government spending, public sector job reductions, and changes to welfare programs. Various Keynesian economists claimed that such policies would be detrimental to the British economy, including Nobel prize winners Paul Krugman, and Joseph Stiglitz. In some sense they were right, but for all the wrong reasons. Austerity in the UK was harmful due to the impact which it had on total expenditure. The reduction in government expenditure caused a reduction in public sector employment, which had a knock on effect in the private sector as lower total spending in the economy led firms to layoff workers. Primarily through these mechanisms austerity policy led to rising unemployment, and a general reduction in standards of living. However, this is not inevitable. Following the recession the US adopted a very similar set of austerity policies to the UK, if anything they were slightly more radical. Just as economists did in the UK, a letter signed by 350 Keynesian economists suggested that this might push the US economy into recession. The US budget deficit was then reduced from roughly $1,050 billion in 2012 to $550 billion in 2013. Despite this, there was never an equivalent 'double dip' recession, as was experienced in the UK and EU.This is because the Federal Reserve adopted sufficiently expansionary monetary policy to offset the impact of the reduction in government expenditure on NGDP (total expenditure). While government expenditure fell, this was negated by the increase in private sector expenditure, meaning there was no significant increase in unemployment. Had the Bank of England adopted similar monetary policy, the country undoubtedly would have fared far better during the austerity period. Austerity in the UK was not harmful because government expenditure fell, as many will often suggest, but instead because inappropriate monetary policy allowed total expenditure to fall. 

So, that answers this Telegraph piece: Can we really trust Britain's economic data?So, what time's the footie then? Ah, you'd like a little more would you? Yes, the things said are true, an economy is a big complicated thing, difficult to measure, best possible is being done and so on. But we find an extra 2% of GDP down the back of the sofa - from which we can conclude that detailed Keynesian demand management is a very silly idea. But there's a much, much, larger problem here. We have endless whingeing about child poverty levels - which are something we don't even measure. For poverty is now defined as less than 60% of median household income. So we're measuring inequality of household income, not poverty at all. Beyond that even in these days of late blooming fertility those with children are going to be younger than those who have had them - and household income does tend to rise with age. You know, career progression, all that stuff. Our measure of wealth deliberately excludes everything the government does about wealth. Currently everyone else pays £6k a year in taxes so your kids can fail their GCSEs. That's wealth you've got which isn't included in any analysis either of total wealth or wealth distribution. Similarly the NHS. OK, it's health care that's indifferent at best and yet purely by being alive in this place at this time you've a lifetime supply of it. Something not included in our wealth statistics. They don't even include the state pension in the pensions wealth statistics. Let alone the wider benefits system which can indeed be modelled like an insurance policy and so have a capital value.And that's before we get to consumer wealth. Everyone's a supercomputer in their pocket, WhatsApp makes international phone calls free to everyone - the Duke of Westminster and the most recent asylum seeker together. The economic data we've got simply is not fit - as with that Keynesian demand management idea - for the purposes people try to use it for. We certainly can't trust it because it's measuring the wrong things for any useful purpose.Measuring the wrongs things and badly - no, that's not the evidence base upon which to run a polity.

My first post described a few anecdotes about what a warm person Bob Lucas was, and such a great colleague. Here I describe a little bit of his intellectual influence, in a form that is I hope accessible to average people.The "rational expectations" revolution that brought down Keynesianism in the 1970s was really much larger than that. It was really the "general equilibrium" revolution. Macroeconomics until 1970 was sharply different from regular microeconomics. Economics is all about "models," complete toy economies that we construct via equations and in computer programs. You can't keep track of everything in even the most beautiful prose. Microeconomic models, and "general equilibrium" as that term was used at the time, wrote down how people behave — how they decide what to buy, how hard to work, whether to save, etc.. Then it similarly described how companies behave and how government behaves. Set this in motion and see where it all settles down; what prices and quantities result. But for macroeconomic issues, this approach was sterile. I took a lot of general equilibrium classes as a PhD student — Berkeley, home of Gerard Debreu was strong in the field. But it was devoted to proving the existence of equilibrium with more and more general assumptions, and never got around to calculating that equilibrium and what it might say about recessions and government policies. Macroeconomics, exemplified by the ISLM tradition,  inhabited a different planet. One wrote down equations for quantities rather than people, for example that "consumption" depended on "income," and investment on interest rates. Most importantly, macroeconomics treated each year as a completely separate economy. Today's consumption depended on today's income, having nothing to do with whether people expected the future to look better or worse. Economists recognized this weakness, and a vast and now thankfully forgotten literature tried fruitlessly to find "micro foundations" for Keynesian economics. But building foundations under an existing castle doesn't work. The foundations want a different castle. Bob's "islands" paper is famous, yes, for a complete model of how unexpected money might move output in the short run and not just raise inflation. But you can do that with a half a page of simple math, and Bob's paper is hard to read. It's deeper contribution, and the reason for that difficulty, is that Bob wrote out a complete "general equilibrium" model. People, companies and government each follow described rules of behavior. Those rules are derived as being the optimal thing for people and companies to do given their environment. And they are forward-looking. People think about how to make their whole lives as pleasant as possible, companies to maximize the present value of profits. Prices adjust so supply = demand. Bob said, by example, that we should do macroeconomics by writing down general equilibrium models. General equilibrium had also been abandoned by the presumption that it only studies perfect economies. Macroeconomics is really about studying how things go wrong, how "frictions" in the economy, such as the "sticky" wages underlying Keynesian thinking, can produce undesirable and unnecessary recessions. But here too, Bob requires us to write down the frictions explicitly. In his model, people don't see the aggregate price level right away, and do the best they can with local information. That is the real influence of the paper  and Bob's real influence in the profession. (Current macroeconomic modeling reflects the fact that the Fed sets interest rates, and does not control the money supply.) You can see this influence in Tom Sargent's textbooks. The first textbook has an extensive treatment of Keynesian economics. It's about the most comprehensible treatment there is — but it is no insult to Tom to say that in that book you can see how Keynesian economics really doesn't hang together. Tom describes how, the minute he learned from Bob how to to general equilibrium, everything changed instantly. Rational expectations was, like any other advance, a group effort. But what made Bob the leader was that he showed the rest how to do general equilibrium. This is the heart of my characterization that Bob is the most important macroeconomist of the 20th century. Yes, Keynes and Friedman had more policy impact, and Friedman's advocacy of free markets in microeconomic affairs is the most consequential piece of 20th century economics. But within macroeconomics, there is before Lucas and after Lucas.  Everyone today does economics the Lucas way. Even the most new-Keynesian article follows the Lucas rules of how to do economics. Once you see models founded on complete descriptions of people, businesses, government, and frictions, you can see the gaping holes in standard ISLM models. This is some of his stinging critique, such as "after Keynesian macroeconomics." Sure, if people's income goes up they are likely to consume more, as the Keynesians posited. But interest rates, wages, and expectations of the future also affect consumption, which Keynesians leave out. "Cross equations restrictions" and "budget constraints" are missing. Now, the substantive prediction that monetary policy can only move the real economy via unexpected money supply growth did not bear out, and both subsequent real business cycles and new-Keynesianism brought persistent responses. But the how we do macroeconomics part is the enduring contribution. The paper still had enduring practical lessons. Lucas, together with Friedman and Phelps brought down the Phillips curve. This curve, relating inflation to unemployment, had been (and sadly, remains) at the center of macroeconomics. It is a statistical correlation, but like many correlations people got enthused with it and started reading it as stable relationship, and indeed a causal one. Raise inflation and you can have less unemployment. Raise unemployment in order to lower inflation. The Fed still thinks about it in that causal way. But Lucas, Friedman, and Phelps bring a basic theory to it, and thereby realize it is just a correlation, which will vanish if you push on it. Rich guys wear Rolexes. That doesn't mean that giving everyone a Rolex will have a huge "multiplier" effect and make us all rich. This is the essence of the "Lucas critique" which is a second big contribution that lay readers can easily comprehend. If you push on correlations they will vanish. Macroeconomics was dedicated to the idea that policy makers can fool people. Monetary policy might try to boost output in a recession with a surprise bit of money growth. That will wok once or twice. But like the boy who cried wolf, people will catch on, come to expect higher money growth in recessions and the trick won't work anymore. Bob showed here that all the "behavioral" relations of Keynesian models will fall apart if you exploit them for policy, or push on them, though they may well hold as robust correlations in the data. The "consumption function" is the next great example. Keynesians noticed that when income rises people consume more, so write a consumption function relating consumption to income. But, following Friedman's great work   on consumption, we know that correlation isn't always true in the data. The relation between consumption and income is different across countries (about one for one) than it is over time (less than one for one). And we understand that with Friedman's theory: People, trying to do their best over their whole lives don't follow mechanical rules. If they know income will fall in the future, they consume a lot less today, no matter what today's current income. Lucas showed that people who behave this sensible way will follow a Keynesian consumption function, given the properties of income overt the business cycle. You will see a Keynesian consumption function. Econometric estimates and tests will verify a Keynesian consumption function. Yet if you use the model to change policies, the consumption function will evaporate. This paper is devastating. Large scale Keynesian models had already been constructed, and used for forecasting and policy simulation. It's natural. The model says, given a set of policies (money supply, interest rates, taxes, spending) and other shocks, here is where the economy goes. Well, then, try different policies and find ones that lead to better outcomes. Bob shows the models are totally useless for that effort. If the policy changes, the model will change. Bob also showed that this was happening in real time. Supposedly stable parameters drifted around. (This one is also very simple mathematically. You can see the point instantly. Bob always uses the minimum math necessary. If other papers are harder, that's by necessity not bravado.) This devastation is sad in a way. Economics moved to analyzing policies in much simpler, more theoretically grounded, but less realistic models. Washington policy analysis sort of gave up. The big models lumber on, the Fred's FRBUS for example, but nobody takes the policy predictions that seriously. And they don't even forecast very well. For example, in the 2008 stimulus, the CEA was reduced to assuming a back of the envelope 1.5 multiplier, this 40 years after the first large scale policy models were constructed. Bob always praised the effort of the last generation of Keynesians to write explicit quantitative models, to fit them to data, and to make numerical predictions of various policies. He hoped to improve that effort. It didn't work out that way, but not by intention. This affair explains a lot of why economists flocked to the general equilibrium camp. Behavioral relationships, like what fraction of an extra dollar of income you consume, are not stable over time or as policy changes. But one hopes that preferences, — how impatient you are, how much you are willing to save more to get a better rate of return — and technology — how much a firm can produce with given capital and labor — do not change when policy changes. So, write models for policy evaluation at the level of preferences and technology, with people and companies at the base, not from behavioral relationships that are just correlations. Another deep change: Once you start thinking about macroeconomics as intertemporal economics — the economics that results from people who make decisions about how to consume over time, businesses make decisions about how to produce this year and next — and once you see that their expectations of what will happen next year, and what policies will be in place next year are crucial, you have to think of policy in terms of rules, and regimes, not isolated decisions. The Fed often asks economists for advice, "should we raise the funds rate?" Post Lucas macroeconomists answer that this isn't a well posed question. It's like saying "should we cry wolf?" The right question is, should we start to follow a rule, a regime, should we create an institution, that regularly and reliably raises interest rates in a situation like the current one? Decisions do not live in isolation. They create expectations and reputations. Needless to say, this fundamental reality has not soaked in to policy institutions. And that answer (which I have tried at Fed advisory meetings) leads to glazed eyes. John Taylor's rule has been making progress for 30 years trying to bridge that conceptual gap, with some success.  This was, and remains, extraordinarily contentious. 50 years later, Alan Blinder's book, supposedly about policy, is really one long snark about how terrible Lucas and his followers are, and how we should go back to the Keynesian models of the 1960s. Some of that contention comes back to basic philosophy.  The program applies standard microeconomics: derive people's behaviors as the best thing they can do given their circumstances. If people pick the best combination of apples and bananas when they shop, then also describe consumption today vs. tomorrow as the best they can do given interest rates. But a lot of economics doesn't like this "rational actor" assumption. It's not written in stone, but it has been extraordinarily successful. And it imposes a lot of discipline. There are a thousand arbitrary ways to be irrational.  Somehow though, a large set of economists are happy to write down that people pick fruit baskets optimally, but don't apply the same rationality to decisions over time, or in how they think about the future. But "rational expectations" is really just a humility condition. It says, don't write models in which the predictions of the model are different from the expectations in the model. If you do, if your model is right, people will read the model and catch on, and the model won't work anymore. Don't assume you economist (or Fed chair) are so much less behavioral than the people in your model. Don't base policy on an attempt to fool the little peasants over and over again. It does not say that people are big super rational calculating machines. It just says that they eventually catch on. Some of the contentiousness is also understandable by career concerns. Many people had said "we should do macro seriously like general equilibrium." But it isn't easy to do. Bob had to teach himself, and get the rest of us to learn, a range of new mathematical  and modeling tools to be able to write down interesting general equilibrium models. A 1970 Keynesian can live just knowing how to solve simple systems of linear equations, and run regressions.  To follow Bob and the rational expectations crowd, you had to learn linear time-series statistics, dynamic programming, and general equilibrium math. Bob once described how tough the year was that it took him to learn functional analysis and dynamic programming. The models themselves consisted of a mathematically hard set of constructions. The older generation either needed to completely retool, fade away, or fight the revolution. Some good summary words: Bob's economics uses"rational expectations," or at least forward-looking and model-consistent expectations. Economics becomes "intertemporal," not "static" (one year at a time). Economics is "stochastic" as well as "dynamic," we can treat uncertainty over time, not just economies in which everyone knows the future perfectly. It applies "general equilibrium" to macroeconomics. And I've just gotten to the beginning of the 1970s. When I got to Chicago in the 1980s, there was a feeling of "well, you just missed the party." But it wasn't true. The 1980s as well were a golden age. The early rational expectations work was done, and the following real business cycles were the rage in macro. But Bob's dynamic programming, general equilibrium tool kit was on a rampage all over dynamic economics. The money workshop was one creative use of dynamic programs and interetempboral tools after another one, ranging from taxes to Thai villages (Townsend). I'll mention two. Bob's consumption model is at the foundation of modern asset pricing. Bob parachuted in, made the seminal contribution, and then left finance for other pursuits. The issue at the time was how to generalize the capital asset pricing model. Economists understood that some stocks pay higher returns than others, and that they must do so to compensate for risk. The understood that the risk is, in general terms, that the stock falls in some sense of bad times. But how to measure "bad times?" The CAPM uses the market, other models use somewhat nebulous other portfolios. Bob showed us that at least in the purest theory, that stocks must pay higher average returns if they fall when consumption falls. (Breeden also constructed a consumption model in parallel, but without this "endowment economy" aspect of Bob's) This is the purest most general theory, and all the others are (useful) specializations. My asset pricing book follows. The genius here was to turn it all around. Finance had sensibly built up from portfolio theory, like supply and demand: Given returns, what stocks do you buy, and how much to you save vs. consume? Then, markets have to clear find the stock prices, and thus returns, given which people will buy exactly the amount that's for sale and consume what is produced. That's hard. (Technically, finding the vector of prices that clears markets is hard. Yes, N equations in N unknowns, but they're nonlinear and N is big.)  Bob instead imagined that consumption is fixed at each moment in time, like a desert island  in which so many coconuts fall each day and you can't store them or plant them. Then, you can just read prices from people's preferences. This gives the same answer as if the consumption you assume is fixed had derived from a complex production economy. You don't have to solve for prices that equate supply and demand. Brilliantly, though prices cause consumption to individual people, consumption causes prices in aggregate. This is part of Bob's contribution to the hard business of actually computing quantitative models in the stochastic dynamic general equilibrium tradition. Bob, with Nancy Stokey also took the new tools to the theory of taxation. (Bob Barro also was a founder of this effort in the late 1980s.) You can see the opportunity: we just learned how to handle dynamic (overt time, expectations of tomorrow matter to what you do today) stochastic (but there is uncertainty about what will happen tomorrow) economics (people make explicit optimizing decisions) for macro. How about taking that same approach to taxes? The field of dynamic public finance is born. Bob and Nancy, like Barro, show that it's a good idea for governments to borrow and then repay, so as to spread the pain of taxes evenly over time. But not always. When a big crisis comes, it is useful to execute a "state contingent default." The big tension of Lucas-Stokey (and now, all) dynamic public finance: You don't want any capital taxes for the incentive effects. If you tax capital, people invest less, and you just get less capital. But once people have invested, a capital tax grabs revenue for the government with no economic distortion. Well, that is, if you can persuade them you'll never do it again. (Do you see expectations, reputations, rules, regimes, wolves in how we think of policy?) Lucas and Stoney say, do it only very rarely to balance the disincentive of a bad reputation with the need to raise revenue in once a century calamities. Bob went on, of course, to be one of the founders of modern growth theory. I always felt he deserved a second Nobel for this work. He's absolutely right. Once you look at growth, it's hard to think about anything else. The average Indian lives on $2,000 per year. The average American, $60,000. That was $15,000 in 1950. Nothing else comes close. I only work on money and inflation because that's where I think I have answers. For us mortals, good research proceeds where you think you have an answer, not necessarily from working on Big Questions. Bob brilliantly put together basic facts and theory to arrive at the current breakthrough. Once you get out of the way, growth does not come from more capital, or even more efficiency. It comes from more and better ideas. I remember being awed by his first work for cutting through the morass and assembling the facts that only look salient in retrospect. A key one: Interest rates in poor countries are not much higher than they are in rich countries. Poor countries have lots of workers, but little capital. Why isn't the return on scarce capital enormous, with interest rates in the hundreds of percent, to attract more capital to poor countries? Well, you sort of know the answer, that capital is not productive in those countries.  Productivity is low, meaning those countries don't make use of better ideas on how to organize production.  Ideas too are produced by economics, but, as Paul Romer crystallized, they are fundamentally different from other goods. If I produce an idea, you can use it without hurting my use of it. Yes, you might drive down the monopoly profits I gain from my intellectual property. But if you use my Pizza recipe, that's not like using my car. I can still make Pizza, where if you use my car I can't go anywhere. Thus, the usual free market presumption that we will produce enough ideas is false. (Don't jump too quickly to advocate government subsides for ideas. You have to find the right ideas, and governments aren't necessarily good at subsidizing that search.) And the presumption that intellectual property should be preserved forever is also false. Once produced it is socially optimal for everyone to use it. I won't go on. It's enough to say that Bob was as central to the creation of idea-based growth theory, which dominates today, as he was to general equilibrium macro, which also dominates today.Bob is an underrated empiricist. Bob's work on the size distribution of firms (great tweet summary by Luis Garicano) similarly starts from basic facts of the size distribution of firms and the lack of relationship between size and growth rates. It's interesting how we can go on for years with detailed econometric estimates of models that don't get basic facts right. I loved Bob's paper on money demand for the Carnegie Rochester conference series. An immense literature had tried to estimate money demand functions with dynamics, and was pretty confusing. It made a basic mistake, by looking at first differences rather than levels and thereby isolating the noise and drowning out the signal. Bob made a few plots, basically rediscovered cointegration all on his own, and made sense of it all. And don't forget the classic international comparison of inflation-output relations. Countries with volatile inflation have less Phillips curve tradeoff, just as his islands model featuring confusion between relative prices and the price level predicts. One last note to young scholars. There is a tendency today to value people by the number of papers they produce, and how quickly they rise through the ranks. Read Bob's CV. He wrote about one paper a year, starting quite late in life. But, as Aesop said, they were lions. In his Nobel prize speech, Bob also passed on that he and his Nobel-winning generation at Chicago always felt they were in some backwater, where the high prestige stuff was going on at Harvard and MIT. You never know when it might be a golden age. And the AER rejected his islands paper (as well as Akerlof's lemons). If you know it's good, revise and try again. I will miss his brilliant papers as much as his generous personality. Update: See Ivan Werning's excellent "Lucas Miracles" for an appreciation by a real theorist. 

Political economists often place the state at the centre of explanations of change in capitalism. The emergence of a 'welfare' or 'nation building' state during the twentieth century reflects the advance of democratic movements and Keynesian inspired macroeconomic management. More recently neoliberalism is associated with fiscal austerity enforced through the rise of corporate and financial power. Shifts in state finances, and how states finances are accounted for, were central to these broader political-economic shifts.
In a recent open access article published in the journal Critical Perspectives on Accounting, as part of a forthcoming special issue on 'the future of the state', we bring state theory into conversation with critical accounting literature to explore the relationship between fiscal accounting and capitalist change. Drawing on Joseph Schumpeter's fiscal sociology and his concept of the 'tax state', we connect changes in fiscal practice to turning points in the reorganisation of the state's role within capitalism [...]
The post The history and future of the tax state I: Fiscal accounting and capitalist change appeared first on Progress in Political Economy (PPE).

By the standards of mainstream media coverage of technical economics, Peter Coy's coverage of HANK (Heterogeneous Agent New Keynesian) models in the New York Times was actually pretty good. 1) Representative agents and distributions. Yes, it starts with the usual misunderstanding about "representative agents," that models assume we are all the same. Some of this is the standard journalist's response to all economic models: we have simplified the assumptions, we need more general assumptions. They don't understand that the genius of economic theory lies precisely in finding simplified but tractable assumptions that tell the main story. Progress never comes from putting more ingredients and stirring the pot to see what comes out. (I mean you, third year graduate students looking for a thesis topic.) But in this case many economists are also confused on this issue. I've been to quite a few HANK seminars in which prominent academics waste 10 minutes or so dumping on the "assumption that everyone is identical." There is a beautiful old theorem, called the "social welfare function." (I learned this in graduate school in fall 1979, from Hal Varian's excellent textbook.) People can have almost arbitrarily different preferences (utility functions), incomes and shocks, companies can have almost arbitrarily different characteristics (production functions),  yet the aggregate economy behaves as if there is a single representative consumer and representative firm. The equilibrium path of aggregate consumption, output,  investment, employment, and the prices and interest rates of that equilibrium are the same as those of an economy where everyone and every firm is the same, with a "representative agent" consumption function and "representative firm" production function.  Moreover, the representative agent utility function and representative firm production function need not look anything like those of any particular individual person and firm. If I have power utility and you have quadratic utility, the economy behaves as if there is a single consumer with something in between. Defining the job of macroeconomics to understand the movement over time of aggregates -- how do GDP, consumption, investment, employment, price level, interest rates, stock prices etc. move over time, and how do policies affect those movements -- macroeconomics can ignore microeconomics. (We'll get back to that definition in a moment.) Now uniting macro and micro is important. Macro estimation being what it is, it would be awfully nice to use micro evidence. The program kicked off by Kydland and Prescott to "calibrate" macro models from micro evidence would be very useful. Kydland and Prescott may have had a bit of grass-is-greener optimism about just how much precise evidence macroeconomists have on firms and people, but it's a good idea. Adding up micro evidence to macro is hard, however. Here "aggregation theory," often confused with the "social welfare function" theorem comes up, more as a nightmare from graduate school. The conditions under which the representative agent preferences look like individual people are much more restricted. Like all good theorems, this one rests on assumptions, and the assumptions are false. The crucial assumption is complete markets, and in particular complete risk sharing: There is an insurance market in which you can be compensated for every risk, in particular losing your job.  A generalized form still works, however. There is still a representative agent, but it cares about distributions. The representative agent utility function depends on aggregate consumption, aggregate labor supply but now also statistics about the distribution of consumption across people. In asset pricing, the Constantinides-Duffie model is a great example: the cross-sectional variance of consumption becomes a crucial state variable for the value of the stock market, not just aggregate consumption. All economic theorems are false of course, in that the assumptions are not literally true. The question is, how false? Conventional macroeconomics comes down to a description of how aggregates evolve over time, based on past aggregates: [aggregate income, consumption, employment, inflation... next year ] = function of [aggregate income, consumption, employment, inflation, policy variables... this year ]  + unforecastable shocks. That's it. That's what macroeconomics is. Theory, estimation and calibration to figure out the function. [Update. I added policy variables, e.g. interest rates, to the function. And, the point of macro is to figure out how policies affect the economy, and furthermore with an objective in hand to derive optimal policies. Thanks François Velde for pointing out the omissions in comments.] If HANK is useful to macroeconomics, then, it must be that adding distributional statistics helps to describe aggregate dynamics. Reality must be [aggregate income, consumption, employment, inflation... next year ] = function of [aggregate income, consumption, employment, inflation, distribution of consumption, employment, etc.,  policy variables,... this year ]  + unforecastable shocks. So here is a central question I have for HANK modelers: Is that true? Do statistics on the distribution across people of economic variables really help us to forecast or understand aggregate dynamics? So far, my impression is, not much. The social welfare function theorem can be wrong in its assumptions, yet still a pretty good approximation. And "heterogeneity" has been around macro for a long time, but never has seemed to matter much in the end. (The investment literature of the early 1990s is a great example.) But I would be happy to be proved wrong. This post is as much a suggestion for HANK modelers as a critique. Another possibility: Maybe HANK is about aggregation after all. Can we actually use micro evidence, and add it up constructively, to learn what the representative agent - social welfare function is? Even before HANK, there were good examples. For example, the literature on labor supply: Macro models want people to work more in response to temporarily higher wages. Most individual people work 8 hours a day or zero, so micro evidence finds a small response. But a small number of people move from non-work to work as wages rise. So the representative agent can have a much larger elasticity than individual people. And, you have to understand labor market structure, and the distribution of who is available to work to add up from micro to macro evidence.  Here, I would like to know the basic functional form -- how much does the SWF care about today vs. tomorrow, risk, work vs leisure, as well as any distributional effect? 2) Income effectsCoy also goes on with the usual New York Times schtick about how dumb and irrational all the little hoi polloi are. (Of course we of the elite and the federal government handing out nudges would never be behavioral.) But you don't need HANK to assume that the representative investor is dumb either. He goes on to describe pretty well where the current literature is. Behind this is, however, one of the major features of HANK models so far. One of its most important uses has been to put current income in the IS equation. (Economists talk amongst yourselves for a bit while I explain this to regular people. So far, the central description of demand in new Keynesian models is based on "intertemporal substitution:" When the real interest rate is higher, you consume a bit less today, save a bit more, so that you can consume a lot more tomorrow. That is the crucial mechanism by which higher real interest rates (say, induced by the Fed) lower demand today. Old Keynesian models didn't have people in them at all, but hypothesized that consumption simply follows income. That adds a more powerful mechanism, the "multiplier:" an initial income drop lowers consumption, which lowers income and around we go. )HANK models often add some "hand to mouth" consumers. Some people think about today vs. the future, but others just eat what income they make today. You can get this out of "rational, liquidity constrained" people, but that's typically not enough. To get significant effects, you need people who just behave that way. So,  there is this little bit of behaviorism in many HANK models. But it's a little spice in the otherwise Lucas soup. In equations, the standard model says consumption today = expected consumption tomorrow - (number) x real interest rateAfter an immense amount of algebra and computer time, HANK models allow you to writeconsumption today = (number) x income today + (number) x expected consumption tomorrow - (number) x real interest rate New Keynesian models were invented on the hope they would turn out to be holy water sprinkled on old-Keynesian thinking, for example justifying big spending multipliers and strong monetary policy. They turned out to be nothing at the sort once you read the equations. A movement is underway to modify (torture?) new-Keynesian models to look like old-Keynesian models, to bring macro back to roughly the 1976 edition of Dornbush and Fisher's textbook. Complex expectation formation theories and this aspect of HANK can be digested that way. So here is my second question for HANK modelers: Is this it? When we boil it all down to the linearized equations of the model you take to data, to explain aggregates and monetary and fiscal policy, is there a big bottom line beyond an excuse to revive bits of the Keynesian consumption function? That too is an honest question, and perhaps a suggestion--show us the textbook back of the envelope bottom line model. (It would be awfully nice if distributions mattered here too, theoretically, empirically, and quantitatively.) 3) Micro implications of macro Maybe you disagreed a few paragraphs ago with my definition of macroeconomics, as only concerned with the movement of aggregates over time. Talking with some of my HANK colleagues, a different purpose is at work -- figuring out the effects of macroeconomics on different people. Recessions fall harder on those who lose jobs, and certain income and other groups; harder on some industries and areas than others. Here HANK dovetails with concerns over income diversity and "equity." That's a perfectly good reason to study it, but let's then be clear. If that's the case, HANK really doesn't change our understanding of how policies and events move aggregates around, it is really just about understanding how those aggregates affect different people differently. That may change calculations of optimal monetary policy. If the objective function cares negatively about income diversity, then adding HANK may produce a model that makes no difference at all for the effect of monetary policy on aggregates, but gives a greater weight to employment vs. inflation. ("May!" Inflation also falls harder on people experiencing low incomes, so concerns for equity could go the other way too. Thanks to a correspondent for pointing that out.)  Many models have observationally equivalent predictions for aggregates but different welfare implications, and the same model can have different welfare implications if you put in different preferences for distributions across people. But surely HANK has more to offer than a long-winded excuse for dovishness towards tolerating inflation in place of unemployment. Also, in the big picture this seems like a classic answer in search of a question. If you care about the less fortunate, you start with the big issues: crime, awful schools, family breakdown, opportunity. The additional benefit for the less fortunate from the level of the overnight federal funds rate might be fun to isolate in a model, but we are really staring at a caterpillar on a leaf of a tree and missing the forest of economic misfortune. 4) Last thoughtsI hesitate to write, as I am a consumer not a producer of HANK research, and thus will probably get things wrong or show my limited knowledge of the literature. Please fill the comments with corrections, amplifications, pointers to good papers, etc. There is a tendency in economics to pursue a new technical possibility without really knowing where it's going or why. That's not unhealthy; figure out what you can do first, and what to do later. The why always does come later.  This was true of rational expectations, real business cycles, new-Keynesian models and more. Now that HANK is pretty well developed and is coming out in public, with admiring New York Times articles, it is worth assessing the why, the bottom line, what it does. I'm also hesitant to write and especially too critically. I vividly recall being in grad school, and some speaker (I mercifully forgot who) went on a tirade about all these young whippersnappers using too much math and not enough intuition and just being in love with building models. I vowed if I ever thought that I would retire. What do we say to the angel of old age? Not today. Bring it on, and let's all figure out what it means.Update:  Alessandro Davis comments below, reminding me of their recent QJE paper "Imperfect Risk Sharing and the Business Cycle." This paper evaluates directly the question, how much does heterogeneity matter for aggregate dynamics? The headline answer is "not much, though maybe more at the zero bound." deviations from perfect risk sharing implied by this class of models account for only 7% of output volatility on average but can have sizable output effects when nominal interest rates reach their lower bound. Now, 7% might actually be a lot. A little secret of contemporary macro models is that none of them explain a lot of output volatility. In my above characterization aggregates next year = function of aggregates today + shocks, the shocks are big and account for most variation in aggregates. Most inflation comes from inflation shocks, not movements in other variables like employment, especially as fed through a model. This isn't necessarily a failing of models. New Keynesian models are designed to understand how monetary policy affects output, not to explain why output varies. Milton Friedman thought that most business cycles were due to monetary policy mistakes, so understanding the former is the same as the latter, but he seems to have been wrong about that, at least since 1982.  Or maybe not. The paper's computation takes heterogene in the data, and asks how much does that affect the new-Keynesian model's predictions for output, employment, etc. I have in mind a slightly different question: Even without much theory, how much can data on heterogeneity actually improve forecasts of output, employment, etc. Do distributional variables improve VAR forecasts? Let me know if you have an answer to that one. The paper has a crystal clear summary of the representative agent theorem, and its important extension. They show how distributional variables enter in to a representative agent representation as simple "wedges." Using a representative agent does not mean you assume all people are identical! There is also a great literature review on the general understanding that distributional variables don't matter much for aggregates, starting with Krussell and Smith.  A parallel literature in finance qualitatively examined the beautiful Constantinides-Duffie mechanism, finding that uninsured idiosyncratic risk isn't large enough or variable enough to account for asset pricing puzzles. So far -- that's all from the 1990s and a lot of the point of HANK is to reverse that impression. UpdateSee Matthew Rognlie's superb answer below.  I ask a lot of questions but seldom get such clear and detailed answers!  Thanks for the short course on Hank model big picture! Update 2 Ben Moll writes Hi John, thanks a lot for the very thoughtful post. Lots of great food for thought. In case you hadn't seen it, Tom Sargent posted a new paper a few days ago that has a really great discussion of the main takeaways from HANK. See in particular sections 5 and 7. For example, see the point that HANK "challenges the neoclassical synthesis and a widely-believed prescription for separating macro policy design from policies to redistribute income and wealth." But plenty of other great points there too. Finally, yes, Matt Rognlie's response is really fantastic.Sargent's paper is here. It's fantastic. I'm going to save a review for a separate blog post. 

Yes, OK, slow time of year, PR attempts to get a company written up will work well right now: AI sparks revolution in how much supermarkets charge you for foodDigital labelling can pass on price fluctuations more quickly and cut wasteYes, super and that might even be the effect. But the driver is, we very strongly suspect, this: electronic shelf labels (ESLs), the first step towards dynamic pricing, had been introduced in a small number of existing shops,……..Retail expert Clare Bailey said the move to digital labelling is the first step towards a "dynamic pricing model" in supermarkets as they look to reduce labour, ….. costsWe've all seen this in a shop, an individual clacking out new price labels to stick on a shelf of something or other. That person costs the shop about £10 an hour this year, it'll soon be about £11 just in wages alone (then add NI, benefits etc) and so the hunt is on to reduce labour costs. One central data entry to change the price on a whole shelf of product, job's a good 'un.We can think of this as just tech reducing labour costs, or labour costs being forced up and thereby inducing the job killing use of technology. Either works.Far more fun, to us at least, is that this begins to destroy a core tenet of New Keynesian economics. The idea of menu costs is central - it explains price stickiness. Prices do not smoothly change, they move in shuddery jumps. For there's a cost to changing the price - the cost of reprinting the menu - so it's only worth doing that when the underlying has changed enough to justify that cost of actually making the price change. This is true too. It's also why the New Classical and Real Business Cycle theories seem not to explain the world quite right, but New Keynesian seem to do better. Which is why every central bank and Treasury economic model is, by and large, New Keynesian.That's all a recent development, certainly recent decades. Which is where the fun comes in really. For those real world economic models have all zeroed in on a specific explanatory structure just as that structure becomes non-explanatory. If changing prices is now the one single entry in a central database for a shop, possibly for an entire chain, then menus costs are much less of an issue. The world is moving closer to those RBC and New Classical models where prices change swiftly and near costlessly and so the economy as a whole reacts near instantly to change. Yes, obviously, these are all tendencies, not absolutes. But we really do think that it's terribly fun that just as the orthodoxy narrows in on something generally agreed that it is also becoming untrue.As in that old joke about economics exams. Universities still use the same questions they did a century ago - it's the answers that have changed. Which, actually, they have.

For our last Political Economy seminar in 2023, three recent doctoral graduates will illuminate the diverse applications and insights offered by a political economy approach. From Latin America to East Asia, via Sydney, these three papers will explore the intersections of political economy with other disciplines, such as geography and psychoanalysis, and a range of theoretical traditions from Marxism to post-Keynesian economics to world-ecology. These conceptual resources are applied to crucial and pressing questions about labour’s subordination to economic development, the role of central banks in financial stability, and the relations between nature and the state at the frontiers of commodity exploitation. This panel will give us an opportunity to discuss the connections and contradictions between different applications of a political economy approach and its essential interdisciplinarity.
Presenters:
David Avilés Espinoza, Spatial Political Economy: The Ideology of Nature, state-space, and the Oil Commodity Frontier in Chilean Patagonia
Luciano Carment, Quantitative Easing in Japan: A Critical Evaluation
Christian Caiconte, Theorising the Unconscious in the Study of Political Economy: The Case of Korea
Chair: Adam David Morton
When: 21 November, 12:00-13:30
Where: Social Sciences Building (A02), Room 441
The post Roundtable—The Flight of a Kite: Methodological and Geographical Diversity from Sydney’s Political Economy appeared first on Progress in Political Economy (PPE).

This post takes up from two previous posts (part 1;  part 2), asking just what do we (we economists) really know about how interest rates affect inflation. Today, what does contemporary economic theory say? As you may recall, the standard story says that the Fed raises interest rates; inflation (and expected inflation) don't immediately jump up, so real interest rates rise; with some lag, higher real interest rates push down employment and output (IS); with some more lag, the softer economy leads to lower prices and wages (Phillips curve). So higher interest rates lower future inflation, albeit with "long and variable lags." Higher interest rates -> (lag) lower output, employment -> (lag) lower inflation. In part 1, we saw that it's not easy to see that story in the data. In part 2, we saw that half a century of formal empirical work also leaves that conclusion on very shaky ground. As they say at the University of Chicago, "Well, so much for the real world, how does it work in theory?" That is an important question. We never really believe things we don't have a theory for, and for good reason. So, today, let's look at what modern theory has to say about this question. And they are not unrelated questions. Theory has been trying to replicate this story for decades. The answer: Modern (anything post 1972) theory really does not support this idea. The standard new-Keynesian model does not produce anything like the standard story.  Models that modify that simple model to achieve something like result of the standard story do so with a long list of complex ingredients. The new ingredients are not just sufficient, they are (apparently) necessary to produce the desired dynamic pattern. Even these models do not  implement the verbal logic above. If the pattern that high interest rates lower inflation over a few years is true, it is by a completely different mechanism than the story tells. I conclude that we don't have a simple economic model that produces the standard belief. ("Simple" and "economic" are important qualifiers.) The simple new-Keynesian model The central problem comes from the Phillips curve. The modern Phillips curve asserts that price-setters are forward-looking. If they know inflation will be high next year, they raise prices now. So Inflation today = expected inflation next year + (coefficient) x output gap.  \[\pi_t = E_t\pi_{t+1} + \kappa x_t\](If you know enough to complain about \(\beta\approx0.99\) in front of \(E_t\pi_{t+1}\) you know enough that it doesn't matter for the issues here.)Now, if the Fed raises interest rates, and if (if) that lowers output or raises unemployment, inflation today goes down. The trouble is, that's not what we're looking for. Inflation goes down today, (\(\pi_t\))relative to expected inflation next year (\(E_t\pi_{t+1}\)). So a higher interest rate and lower output correlate with inflation that is rising over time.    Here is a concrete example: The plot is the response of the standard three equation new-Keynesian model to an \(\varepsilon_1\) shock at time 1:\[\begin{align} x_t &= E_t x_{t+1} - \sigma(i_t - E_t\pi_{t+1}) \\ \pi_t & = \beta E_t \pi_{t+1} + \kappa x_t \\ i_t &= \phi \pi_t + u_t \\ u_t &= \eta u_{t-1} + \varepsilon_t. \end{align}\] Here \(x\) is output, \(i\) is the interest rate, \(\pi\) is inflation, \(\eta=0.6\), \(\sigma=1\), \(\kappa=0.25\), \(\beta=0.95\), \(\phi=1.2\). In this plot, higher interest rates are said to lower inflation. But they lower inflation immediately, on the day of the interest rate shock. Then, as explained above, inflation rises over time. In the standard view, and the empirical estimates from the last post, a higher interest rate has no immediate effect, and then future inflation is lower. See plots in the last post, or this one from Romer and Romer's 2023 summary:Inflation jumping down and then rising in the future is quite different from inflation that does nothing immediately, might even rise for a few months, and then starts gently going down. You might even wonder about the downward jump in inflation. The Phillips curve makes it clear why current inflation is lower than expected future inflation, but why doesn't current inflation stay the same, or even rise, and expected future inflation rise more? That's the "equilibrium selection" issue. All those paths are possible, and you need extra rules to pick a particular one. Fiscal theory points out that the downward jump needs a fiscal tightening, so represents a joint monetary-fiscal policy. But we don't argue about that today. Take the standard new Keynesian model exactly as is, with passive fiscal policy and standard equilibrium selection rules. It predicts that inflation jumps down immediately and then rises over time. It does not predict that inflation slowly declines over time.  This is not a new issue. Larry Ball (1994) first  pointed out that the standard new Keynesian Phillips curve says that output is high when inflation is high relative to expected future inflation, that is when inflation is declining. Standard beliefs  go the other way: output is high when inflation is rising.  The IS curve is a key part of the overall prediction, and output faces a similar problem. I just assumed above that output falls when interest rates rise. In the model it does; output follows a path with the same shape as inflation in my little plot. Output also jumps down and then rises over time. Here too, the (much stronger) empirical evidence says that an interest rate rise does not change output immediately, and output then falls rather than rises over time. The intuition has even clearer economics behind it: Higher real interest rates induce people to consume less today and more tomorrow. Higher real interest rates should go with higher, not lower, future consumption growth. Again, the model only apparently reverses the sign by having output jump down before rising. Key issuesHow can we be here, 40 years later, and the benchmark textbook model so utterly does not replicate standard beliefs about monetary policy? One answer, I believe, is confusing adjustment to equilibrium with equilibrium dynamics. The model generates inflation lower than yesterday (time 0 to time 1) and lower than it otherwise would be (time 1 without shock vs time 1 with shock). Now, all economic models are a bit stylized. It's easy to say that when we add various frictions, "lower than yesterday" or "lower than it would have been" is a good parable for "goes down over time."  If in a simple supply and demand graph we say that an increase in demand raises prices instantly, we naturally understand that as a parable for a drawn out period of price increases once we add appropriate frictions. But dynamic macroeconomics doesn't work that way. We have already added what was supposed to be the central friction, sticky prices. Dynamic economics is supposed to describe the time-path of variables already, with no extra parables. If adjustment to equilibrium takes time, then model that.  The IS and Phillips curve are forward looking, like stock prices. It would make little sense to say "news comes out that the company will never make money, so the stock price should decline gradually over a few years." It should jump down now. Inflation and output behave that way in the standard model. A second confusion, I think, is between sticky prices and sticky inflation. The new-Keynesian model posits, and a huge empirical literature examines, sticky prices. But that is not the same thing as sticky inflation. Prices can be arbitrarily sticky and inflation, the first derivative of prices, can still jump. In the Calvo model, imagine that only a tiny fraction of firms can change prices at each instant. But when they do, they will change prices a lot, and the overall price level will start increasing right away. In the continuous-time version of the model, prices are continuous (sticky), but inflation jumps at the moment of the shock.  The standard story wants sticky inflation. Many authors explain the new-Keynesian model with sentences like "the Fed raises interest rates. Prices are sticky, so inflation can't go up right away and real interest rates are higher." This is wrong. Inflation can rise right away. In the standard new-Keynesian model it does so with \(\eta=1\), for any amount of price stickiness. Inflation rises immediately with a persistent monetary policy shock. Just get it out of your heads. The standard model does not produce the standard story. The obvious response is, let's add ingredients to the standard model and see if we can modify the response function to look something like the common beliefs and VAR estimates. Let's go. Adaptive expectations We can reproduce standard beliefs about monetary policy with thoroughly adaptive expectations, in the 1970s ISLM form. I think this is a large part of what  most policy makers and commenters have in mind.  Modify the above model to leave out the dynamic part of the intertemporal substitution equation, to just say in rather ad hoc way that higher real interest rates lower output, and specify that the expected inflation that drives the real rate and that drives pricing decisions is mechanically equal to previous inflation, \(E_t \pi_{t+1} = \pi_{t-1}\). We get \[ \begin{align} x_t &= -\sigma (i_t - \pi_{t-1}) \\ \pi_t & = \pi_{t-1} + \kappa x_t .\end{align}\] We can solve this sytsem analytically to \[\pi_t = (1+\sigma\kappa)\pi_{t-1} - \sigma\kappa i_t.\]Here's what happens if the Fed permanently raises the interest rate. Higher interest rates send future inflation down. (\(\kappa=0.25,\ \sigma=1.\)) Inflation eventually spirals away, but central banks don't leave interest rates alone forever. If we add a Taylor rule response \(i_t = \phi \pi_t + u_t\),  so the central bank reacts to the emerging spiral, we get this response to a permanent monetary policy disturbance \(u_t\): The higher interest rate sets off a deflation spiral. But the Fed quickly follows inflation down to stabilize the situation. This is, I think, the conventional story of the 1980s. In terms of ingredients, an apparently minor change of index from \(E_t \pi_{t+1}\) to \(\pi_{t-1}\) is in fact a big change. It means directly that higher output comes with increasing inflation, not decreasing inflation, solving Ball's puzzle.  The change basically changes the sign of output in the Phillips curve. Again, it's not really all in the Phillips curve. This model with rational expectations in the IS equation and adaptive in the Phillips curve produces junk. To get the result you need adaptive expectations everywhere. The adaptive expectations model gets the desired result by changing the basic sign and stability properties of the model. Under rational expectations the model is stable; inflation goes away all on its own under an interest rate peg. With adaptive expectations, the model is unstable. Inflation or deflation spiral away under an interest rate peg or at the zero bound. The Fed's job is like balancing a broom upside down. If you move the bottom (interest rates) one way, the broom zooms off the other way. With rational expectations, the model is stable, like a pendulum.  This is not a small wrinkle designed to modify dynamics. This is major surgery. It is also a robust property: small changes in parameters do not change the dominant eigenvalue of a model from over one to less than one.  A more refined way to capture how Fed officials and pundits think and talk might be called "temporarily fixed expectations." Policy people do talk about the modern Phillips curve; they say inflation depends on inflation expectations and employment. Expectations are not mechanically adaptive. Expectations are a third force, sometimes "anchored," and amenable to manipulation by speeches and dot plots. Crucially, in this analysis, expected inflation does not move when the Fed changes interest rates.  Expectations are then  very slowly adaptive, if inflation is persistent, or if there is a more general loss of faith in "anchoring." In the above new-Keynesian model graph, at the minute the Fed raises the interest rate, expected inflation jumps up to follow the graph's plot of the model's forecast of inflation. As a simple way to capture these beliefs, suppose expectations are fixed or "anchored" at \(\pi^e\). Then my simple model is \[\begin{align}x_t & = -\sigma(i_t - \pi^e) \\ \pi_t & = \pi^e + \kappa x_t\end{align}\]so \[\pi_t = \pi^e - \sigma \kappa (i_t - \pi^e).\] Inflation is expected inflation, and lowered by higher interest rates (last - sign). But those rates need only be higher than the fixed expectations; they do not need to be higher than past rates as they do in the adaptive expectations model. That's why the Fed thinks 3% interest rates with 5% inflation is still "contractionary"--expected inflation remains at 2%, not the 5% of recent adaptive experience.  Also by fixing expectations, I remove the instability of the adaptive expectations model... so long as those expectations stay anchored. The Fed recognizes that eventually higher inflation moves the expectations, and with a belief that is adaptive, they fear that an inflation spiral can still break out.Even this view does not give us any lags, however. The Fed and commenters clearly believe that higher real interest rates today lower output next year, not immediately; and they believe that lower output and employment today drive inflation down in the future, not immediately. They believe something like \[\begin{align}x_{t+1} &= - \sigma(i_t - \pi^e) \\ \pi_{t+1} &= \pi^e + \kappa x_t.\end{align}\] But now we're at the kind of non-economic ad-hockery that the whole 1970s revolution abandoned. And for a reason: Ad hoc models are unstable, regimes are always changing. Moreover, let me remind you of our quest: Is there a simple economic model of monetary policy that generates something like the standard view? At this level of ad-hockery you might as well just write down the coefficients of Romer and Romer's response function and call that the model of how interest rates affect inflation.  Academic economics gave up on mechanical expectations and ad-hoc models in the 1970s. You can't publish a paper with this sort of model. So when I mean a "modern" model, I mean  rational expectations, or at least the consistency condition that the expectations in the model are not fundamentally different from forecasts of the model. (Models with explicit learning or other expectation-formation frictions count too.) It's easy to puff about people aren't rational, and looking out the window lots of people do dumb things. But if we take that view, then the whole project of monetary policy on the proposition that people are fundamentally unable to learn patterns in the economy, that a benevolent Federal Reserve can trick the poor little souls into a better outcome.  And somehow the Fed is the lone super-rational actor who can avoid all those pesky behavioral biases. We are looking for the minimum necessary ingredients to describe the basic signs and function of monetary policy. A bit of irrational or complex expectation formation as icing on the cake, a possible sufficient ingredient to produce quantitatively realistic dynamics, isn't awful. But it would be sad if irrational expectations or other behavior is a necessary ingredient to get the most basic sign and story of monetary policy right. If persistent irrationality is a central necessary ingredient for the basic sign and operation of monetary policy -- if higher interest rates will raise inflation the minute people smarten up; if there is no simple supply and demand, MV=PY sensible economics underlying the basic operation of monetary policy; if it's all a conjuring trick  -- that should really weaken our faith in the whole monetary policy project.  Facts help, and we don't have to get religious about it. During the long zero bound, the same commentators and central bankers kept warning about a deflation spiral, clearly predicted by this model. It never happened. Interest rates below inflation from 2021 to 2023 should have led to an upward inflation spiral. It never happened -- inflation eased all on its own with interest rates below inflation.Getting the desired response to interest rates by making the model unstable isn't tenable whether or not you like the ingredient.  Inflation also surged in the 1970s faster than adaptive expectations came close to predicting, and fell faster in the 1980s.  The ends of many inflations come with credible changes in regime. There is a lot of work now desperately trying to fix new-Keynesian models by making them more old-Keynesian, putting lagged inflation in the Phillips curve, current income in the IS equation, and so forth. Complex learning and expectation formation stories replace the simplistic adaptive expectations here. As far as I can tell, to the extent they work they largely do so in the same way, by reversing the basic stability of the model. Modifying the new-Keynesian modelThe alternative is to add ingredients to the basic new-Keynesian model, maintaining its insistence on real "micro-founded" economics and forward-looking behavior, and describing explicit dynamics as the evolution of equilibrium quantities.  Christiano Eichenbaum and Evans (2005) is one of the most famous examples. Recall these same authors  created the first most influential VAR that gave the "right" answer to the effects of monetary policy shocks. This paper modifies the standard new-Keynesian model with a specific eye to matching impulse response functions. The want to match all impulse-responses, with a special focus on output. When I started asking my young macro colleagues for a standard model which produces the desired response shape, they still cite CEE first, though it's 20 years later. That's quite an accomplishment. I'll look at it in detail, as the general picture is the same as many other models that achieve the desired result. Here's their bottom line response to a monetary policy shock: (Figure from the 2018 Christiano Eichenbaum and Trabandt Journal of Economic Perspectives summary paper.)  The solid line is the VAR point estimate and gray shading is the 95% confidence band. The solid blue line is the main model. The dashed line is the model with only price stickiness, to emphasize the importance of wage stickiness. The shock happens at time 0. Notice the funds rate line that jumps down at that date. That the other lines do not move at time 0 is a result. I graphed the response to a time 1 shock above. That's the answer, now what's the question? What ingredients did they add above the textbook model to reverse the basic sign and jump problem and to produce  these pretty pictures? Here is a partial list: Habit formation. The utility function is  \(log(c_t - bc_{t-1})\). A capital stock with adjustment costs in investment.  Adjustment costs are proportional to investment growth, \([1-S(i_t/i_{t-1})]i_t\), rather than the usual formulation in which adjustment costs are proportional to the investment to capital ratio \(S(i_t/k_t)i_t\). Variable capital utilization. Capital services \(k_t\) are related to the capital stock \(\bar{k}t\) by \(k_t = u_t \bar{k}_t\). The utilization rate \(u_t\) is set by households facing an upward sloping cost \(a(u_t)\bar{k}_t\).Calvo pricing with indexation: Firms randomly get to reset prices, but firms that aren't allowed to reset prices do automatically raise prices at the rate of inflation.Prices are also fixed for a quarter. Technically, firms must post prices before they see the period's shocks.Sticky wages, also with indexation. Households are monopoly suppliers of labor, and set wages Calvo-style like firms. (Later papers put all households into a union which does the wage setting.) Wages are also indexed; Households that don't get to reoptimize their wage still raise wages following inflation. Firms must borrow working capital to finance their wage bill a quarter in advance, and thus pay a interest on the wage bill. Money in the utility function, and money supply control. Monetary policy is a change in the money growth rate, not a pure interest rate target. Whew! But which of these ingredients are necessary, and which are just sufficient? Knowing the authors, I  strongly suspect that they are all necessary to get the suite of results. They don't add ingredients for show. But they want to match all of the impulse response functions, not just the inflation response. Perhaps a simpler set of ingredients could generate the inflation response while missing some of the others. Let's understand what each of these ingredients is doing, which will help us to see (if) they are necessary and essential to getting the desired result. I see a common theme in habit formation, adjustment costs that scale by investment growth, and indexation. These ingredients each add a derivative; they take a standard relationship between levels of economic variables and change it to one in growth rates. Each of consumption, investment, and inflation is a "jump variable" in standard economics, like stock prices. Consumption (roughly) jumps to the present value of future income. The level of investment is proportional to the stock price in the standard q theory, and jumps when there is new information. Iterating forward the new-Keynesian Phillips curve \(\pi_t = \beta E_t \pi_{t+1} + \kappa x_t\), inflation jumps to the discounted sum of future output gaps, \(\pi_t = E_t \sum_{j=0}^\infty \beta^jx_{t+j}.\)  To produce responses in which output, consumption and investment as well as inflation rise slowly after a shock, we don't want levels of consumption, investment, and inflation to jump this way. Instead we want growth rates to do so. With standard utility, the consumer's linearized first order condition equates expected consumption growth to the interest rate, \( E_t (c_{t+1}/c_t) = \delta + r_t \) Habit, with \(b=1\) gives  \( E_t [(c_{t+1}-c_t)/(c_t-c_{t-1})] = \delta + r_t \). (I left out the strategic terms.) Mixing logs and levels a bit, you can see we put a growth rate in place of a level. (The paper has \(b=0.65\) .) An investment adjustment cost function with \(S(i_t/i_{t-1})\) rather than the standard \(S(i_t/k_t)\) puts a derivative in place of a level. Normally we tell a story that if you want a house painted, doubling the number of painters doesn't get the job done twice as fast because they get in each other's way. But you can double the number of painters overnight if you want to do so. Here the cost is on the increase in number of painters each day.   Indexation results in a Phillips curve with a lagged inflation term, and that gives "sticky inflation."  The Phillips curve of the model (32) and (33) is \[\pi_t = \frac{1}{1+\beta}\pi_{t-1} + \frac{\beta}{1+\beta}E_{t-1}\pi_{t+1} + (\text{constants}) E_{t-1}s_t\]where \(s_t\) are marginal costs (more later). The \(E_{t-1}\) come from the assumption that prices can't react to time \(t\) information. Iterate that forward to (33)\[\pi_t - \pi_{t-1} = (\text{constants}) E_{t-1}\sum_{j=0}^\infty \beta^j s_{t+j}.\] We have successfully put the change in inflation in place of the level of inflation. The Phillips curve is anchored by real marginal costs, and they are not proportional to output in this model as they are in the textbook model above. That's important too. Instead,\[s_t = (\text{constants}) (r^k_t)^\alpha \left(\frac{W_t}{P_t}R_t\right)^{1-\alpha}\] where \(r^k\) is the return to capital \(W/P\) is the real wage and \(R\) is the nominal interest rate. The latter term crops up from the assumption that firms must borrow the wage bill one period in advance. This is an interesting ingredient. There is a lot of talk that higher interest rates raise costs for firms, and they are reducing output as a result. That might get us around some of the IS curve problems. But that's not how it works here. Here's how I think it works. Higher interest rates raise marginal costs, and thus push up current inflation relative to expected future inflation. The equilibrium-selection rules and the rule against instant price changes (coming up next) tie down current inflation, so the higher interest rates have to push down expected future inflation. CEE disagree (p. 28). Writing of an interest rate decline, so all the signs are opposite of my stories,  ... the interest rate appears in firms' marginal cost. Since the interest rate drops after an expansionary monetary policy shock, the model embeds a force that pushes marginal costs down for a period of time. Indeed, in the estimated benchmark model the effect is strong enough to induce a transient fall in inflation.But pushing marginal costs down lowers current inflation relative to future inflation -- they're looking at the same Phillips curve just above. It looks to me like they're confusing current with expected future inflation. Intuition is hard. There are plenty of Fisherian forces in this model that want lower interest rates to lower inflation. More deeply,  we see here a foundational trouble of the Phillips curve. It was originally a statistical relation between wage inflation and unemployment. It became a (weaker) statistical relation between price inflation and unemployment or the output gap. The new-Keynesian theory wants naturally to describe a relation between marginal costs and price changes, and it takes contortions to make output equal to marginal costs. Phillips curves fit the data terribly. So authors estimating Phillips curves (An early favorite by Tim Cogley and Argia Sbordone) go back, and separate marginal cost from output or employment. As CET write later, they "build features into the model which ensure that firms' marginal costs are nearly acyclical." That helps the fit, but it divorces the Phillips curve shifter variable from the business cycle! Standard doctrine says that for the Fed to lower inflation it must soften the economy and risk unemployment. Doves say don't do it, live with inflation to avoid that cost. Well, if the Phillips curve shifter is "acyclical" you have to throw all that out the window.  This shift also points to the central conundrum of the Phillips curve. Here it describes the adjustment of prices to wages or "costs" more generally. It fundamentally describes a relative price, not a price level. OK, but the phenomenon we want to explain is the common component, how all prices and wage tie together or equivalently the decline in the value of the currency, stripped of relative price movements. The central puzzle of macroeconomics is why the common component, a rise or fall of all prices and wages together, has anything to do with output, and for us how it is controlled by the Fed. Christiano Eichenbaum and Evans write (p.3) that "it is crucial to allow for variable capital utilization." I'll try explain  why in my own words. Without capital adjustment costs, any change in the real return leads to a big investment jump. \(r=f'(k)\) must jump and that takes a lot of extra \(k\). We add adjustment costs to tamp down the investment response. But now when there is any shock, capital can't adjust enough and there is a big rate of return response. So we need something that acts like a big jump in the capital stock to tamp down \(r=f'(k)\) variability, but not a big investment jump. Variable capital utilization acts like the big investment jump without us seeing a big investment jump. And all this is going to be important for inflation too. Remember the Phillips curve; if output jumps then inflation jumps too. Sticky wages are crucial, and indeed CEE report that they can dispense with sticky prices. One reason is that otherwise profits are countercyclical. In a boom, prices go up faster than wages so profits go up. With sticky prices and flexible wages you get the opposite sign. It's interesting that the "textbook" model has not moved this way. Again, we don't often enough write textbooks. Fixing prices and wages during the period of the shock by assuming price setters can't see the shock for a quarter has a direct effect: It stops any price or wage jumps during the quarter of the shock, as in my first graph. That's almost cheating. Note the VAR also has absolutely zero instantaneous inflation response. This too is by assumption. They "orthogonalize" the variables so that all the contemporaneous correlation between monetary policy shocks and inflation or output is considered part of the Fed's "rule" and none of it reflects within-quarter reaction of prices or quantities to the Fed's actions. Step back and admire. Given the project "find elaborations of the standard new-Keynesian model to match VAR impulse response functions" could you have come up with any of this? But back to our task. That's a lot of apparently necessary ingredients. And reading here or CEE's verbal intuition, the logic of this model is nothing like the standard simple intuition, which includes none of the necessary ingredients. Do we really need all of this to produce the basic pattern of monetary policy? As far as we know, we do. And hence, that pattern may not be as robust as it seems. For all of these ingredients are pretty, ... imaginative. Really, we are a long way from the Lucas/Prescott vision that macroeconomic models should be based on well tried and measured microeconomic ingredients that are believably invariant to changes in the policy regime. CEE argue hard for the plausibility of these microeconomic specifications (see especially the later CET Journal of Economic Perspectives article), but they have to try so hard precisely because the standard literature doesn't have any of these ingredients. The "level" rather than "growth rate" foundations of consumption, investment, and pricing decisions pervade microeconomics. Microeconomists worry about labor monopsony, not labor monopoly; firms set wages, households don't. (Christiano Eichenbam and Trabandt (2016) get wage stickiness from a more realistic search and matching model. Curiously, the one big labor union fiction is still the most common, though few private sector workers are unionized.) Firms don't borrow the wage bill a quarter ahead of time.  Very few prices and wages are indexed in the US. Like habits, perhaps these ingredients are simple stand ins for something else, but at some point we need to know what that something else is. That is especially true if one wants to do optimal policy or welfare analysis. Just how much economics must we reinvent to match this one response function? How far are we really from the ad-hoc ISLM equations that Sims (1980) destroyed? Sadly, subsequent literature doesn't help much (more below). Subsequent literature has mostly added ingredients, including heterogeneous agents (big these days), borrowing constraints, additional financial frictions (especially after 2008), zero bound constraints, QE, learning and complex expectations dynamics. (See CET 2018 JEP  for a good verbal survey.) The rewards in our profession go to those who add a new ingredient. It's very hard to publish papers that strip a model down to its basics. Editors don't count that as "new research," but just "exposition" below the prestige of their journals. Though boiling a model down to essentials is maybe more important in the end than adding more bells and whistles. This is about where we are. Despite the pretty response functions, I still score that we don't have a reliable, simple, economic model that produces the standard view of monetary policy. Mankiw and Reis, sticky expectations Mankiw and Reis (2002) expressed the challenge clearly over 20 years ago. In reference to the "standard" New-Keynesian Phillips curve \(\pi_t = \beta E_t \pi_{t+1} + \kappa x_t\) they write a beautiful and succinct paragraph: Ball [1994a] shows that the model yields the surprising result that announced, credible disinflations cause booms rather than recessions. Fuhrer and Moore [1995] argue that it cannot explain why inflation is so persistent. Mankiw [2001] notes that it has trouble explaining why shocks to monetary policy have a delayed and gradual effect on inflation. These problems appear to arise from the same source: although the price level is sticky in this model, the inflation rate can change quickly. By contrast, empirical analyses of the inflation process (e.g., Gordon [1997]) typically give a large role to "inflation inertia."At the cost of repetition, I emphasize the last sentence because it is so overlooked. Sticky prices are not sticky inflation. Ball already said this in 1994: Taylor (1979, 198) and Blanchard (1983, 1986) show that staggering produces inertia in the price level: prices just slowly to a fall in th money supply. ...Disinflation, however, is a change in the growth rate of money not a one-time shock to the level. In informal discussions, analysts often assume that the inertia result carries over from levels to growth rates -- that inflation adjusts slowly to a fall in money growth. As I see it, Mankiw and Reis generalize the Lucas (1972) Phillips curve. For Lucas, roughly, output is related to unexpected inflation\[\pi_t = E_{t-1}\pi_t + \kappa x_t.\] Firms don't see everyone else's prices in the period. Thus, when a firm sees an unexpected rise in prices, it doesn't know if it is a higher relative price or a higher general price level; the firm expands output based on how much it thinks the event might be a relative price increase.  I love this model for many reasons, but one, which seems to have fallen by the wayside, is that it explicitly founds the Phillips curve in firms' confusion about relative  prices vs. the price level, and thus faces up to the problem why should a rise in the price level have any real effects. Mankiw and Reis basically suppose that firms find out the general price level with lags, so output depends on inflation relative to a distributed lag of its expectations. It's clearest for the price level (p. 1300)\[p_t = \lambda\sum_{j=0}^\infty (1-\lambda)^j E_{t-j}(p_t + \alpha x_t).\] The inflation expression is \[\pi_t = \frac{\alpha \lambda}{1-\lambda}x_t + \lambda \sum_{j=0}^\infty (1-\lambda)^j E_{t-1-j}(\pi_t + \alpha \Delta x_t).\](Some of the complication is that you want it to be \(\pi_t = \sum_{j=0}^\infty E_{t-1-j}\pi_t + \kappa x_t\), but output doesn't enter that way.) This seems totally natural and sensible to me. What is a "period" anyway? It makes sense that firms learn heterogeneously whether a price increase is relative or price level. And it obviously solves the central persistence problem with the Lucas (1972) model, that it only produces a one-period output movement. Well, what's a period anyway? (Mankiw and Reis don't sell it this way, and actually don't cite Lucas at all. Curious.)  It's not immediately obvious that this curve solves the Ball puzzle and the declining inflation puzzle, and indeed one must put it in a full model to do so. Mankiw and Reis (2002) mix it with \(m_t + v = p_t + x_t\) and make some stylized analysis, but don't show how to put the idea in models such as I started with or make a plot.  Their less well known follow on paper  Sticky Information in General Equilibrium (2007) is much better for this purpose because they do show you how to put the idea in an explicit new-Keynesian model, like the one I started with.  They also add a Taylor rule, and an interest rate rather than money supply instrument, along with wage stickiness and a few other ingredients,. They show how to solve the model overcoming the problem that there are many lagged expectations as state variables. But here is the response to the monetary policy shock: Response to a Monetary Policy Shock, Mankiw and Reis (2007). Sadly they don't report how interest rates respond to the shock. I presume interest rates went down temporarily. Look: the inflation and output gap plots are about the same. Except for the slight delay going up, these are exactly the responses of the standard NK model. When output is high, inflation is high and declining.  The whole point was to produce a model in which high output level would correspond to rising inflation. Relative to the first graph, the main improvement is just a slight hump shape in both inflation and output responses. Describing the same model in "Pervasive Stickiness" (2006), Mankiw and Reis describe the desideratum well: The Acceleration Phenomenon....inflation tends to rise when the economy is booming and falls when economic activity is depressed. This is the central insight of the empirical literature on the Phillips curve. One simple way to illustrate this fact is to correlate the change in inflation, \(\pi_{t+2}-\pi_{t-2}\) with [the level of] output, \(y_t\), detrended with the HP filter. In U.S. quarterly data from 1954-Q3 to 2005-Q3, the correlation is 0.47. That is, the change in inflation is procyclical.Now look again at the graph. As far as I  can see, it's not there. Is this version of sticky inflation a bust, for this purpose? I still think it's a neat idea worth more exploration. But I thought so 20 years ago too.  Mankiw and Reis have a lot of citations but nobody followed them. Why not?  I suspect it's part of a general pattern that lots of great micro sticky price papers are not used because they don't produce an easy aggregate Phillips curve. If you want cites, make sure people can plug it in to Dynare. Mankiw and Reis' curve is pretty simple, but you still have to keep all past expectations around as a state variable. There may be alternative ways of doing that with modern computational technology, putting it in a Markov environment or cutting off the lags, everyone learns the price level after 5 years. Hank models have even bigger state spaces! Some more modelsWhat about within the Fed?  Chung,  Kiley, and  Laforte 2010, "Documentation of the Estimated, Dynamic, Optimization-based (EDO) Model of the U.S. Economy: 2010 Version" is one such model.  (Thanks to Ben Moll, in a lecture slide titled "Effects of interest rate hike in U.S. Fed's own New Keynesian model") They describe it as This paper provides documentation for a large-scale estimated DSGE model of the U.S. economy – the Federal Reserve Board's Estimated, Dynamic, Optimization- based (FRB/EDO) model project. The model can be used to address a wide range of practical policy questions on a routine basis.Here are the central plots for our purpose: The response of interest rates and inflation to a monetary policy shock.  No long and variable lags here. Just as in the simple model, inflation jumps down on the day of the shock and then reverts. As with Mankiw and Reis, there is a tiny hump shape, but that's it. This is nothing like the Romer and Romer plot. Smets and Wouters (2007) "Shocks and Frictions in US Business Cycles: A Bayesian DSGE Approach" is about as famous as Christiano Eichenbaum and Evans as a standard new-Keynesian model that supposedly matches data well. It "contains many shocks and frictions. It features sticky nominal price and wage settings that allow for backward inflation indexation, habit formation in consumption, and investment adjustment costs that create hump-shaped responses... and variable capital utilization and fixed costs in production"Here is their central graph of the response to a monetary policy shockAgain, there is a little hump-shape, but the overall picture is just like the one we started with. Inflation mostly jumps down immediately and then recovers; the interest rate shock leads to future inflation that is higher, not lower than current inflation. There are no lags from higher interest rates to future inflation declines. The major difference, I think, is that Smets and Wouters do not impose the restriction that inflation cannot jump immediately on either their theory or empirical work, and Christiano, Eichenbaum and Evans impose that restriction in both places. This is important. In a new-Keynesian model some combination of state variables must jump on the day of the shock, as it is only saddle-path stable. If inflation can't move right away, that means something else does. Therefore, I think, CEE also preclude inflation jumping the next period. Comparing otherwise similar ingredients, it looks like this is the key ingredient for producing Romer-Romer like responses consistent with the belief in sticky inflation. But perhaps the original model and Smets-Wouters are right! I do not know what happens if you remove the CEE orthogonalization restriction and allow inflation to jump on the day of the shock in the date. That would rescue the new-Keynesian model, but it would destroy the belief in sticky inflation and long and variable lags. Closing thoughtsI'll reiterate the main point. As far as I can tell, there is no simple economic model that produces the standard belief. Now, maybe belief is right and models just have to catch up. It is interesting that there is so little effort going on to do this. As above, the vast outpouring of new-Keynesian modeling has been to add even more ingredients. In part, again, that's the natural pressures of journal publication. But I think it's also an honest feeling that after Christiano Eichenbaun and Evans, this is a solved problem and adding other ingredients is all there is to do. So part of the point of this post (and "Expectations and the neutrality of interest rates") is to argue that this is not a solved problem, and that removing ingredients to find the simplest economic model that can produce standard beliefs is a really important task.  Then, does the model incorporate anything at all of the standard intuition, or is it based on some different mechanism al together? These are first order important and unresolved questions!But for my lay readers, here is as far as I know where we are. If you, like the Fed, hold to standard beliefs that higher interest rates lower future output and inflation with long and variable lags, know there is no simple economic theory behind that belief, and certainly the standard story is not how economic models of the last four decades work. Update:I repeat a response to a comment below, because it is so important. I probably wasn't clear enough that the "problem" of high output with inflation falling rather than rising is a problem of models vs. traditional beliefs, rather than of models vs. facts. The point of the sequence of posts, really, is that the traditional beliefs are likely wrong. Inflation does not fall, following interest rate increases, with dependable, long, and perhaps variable lags. That belief is strong, but neither facts, empirical evidence, or theory supports it. ("Variable" is a great way to scrounge data to make it fit priors.) Indeed many successful disinflations like ends of hyperinflations feature a sigh of relief and output surge on the real side. 

 A few days ago I gave a short talk on the subject. I was partly inspired by a little comment made at a seminar, roughly "of course we all know that if prices are sticky, higher nominal rates raise higher real rates, that lowers aggregate demand and lowers inflation." Maybe we "know" that, but it's not as readily present in our models as we think. This also crystallizes some work in the ongoing "Expectations and the neutrality of interest rates" project. The equations are the utterly standard new-Keynesian model. The last equation tracks the evolution of the real value of the debt, which is usually in the footnotes of that model. OK, top right, the standard result. There is a positive but temporary shock to the monetary policy rule, u. Interest rates go up and then slowly revert. Inflation goes down. Hooray. (Output also goes down, as the Phillips Curve insists.) The next graph should give you pause on just how you interpreted the first one. What if the interest rate goes up persistently? Inflation rises, suddenly and completely matching the rise in interest rate! Yet prices are quite sticky -- k = 0.1 here. Here I drove the persistence all the way to 1, but that's not crucial. With any persistence above 0.75, higher interest rates give rise to higher inflation. What's going on? Prices are sticky, but inflation is not sticky. In the Calvo model only a few firms can change price in any instant, but they change by a large amount, so the rate of inflation can jump up instantly just as it does. I think a lot of intuition wants inflation to be sticky, so that inflation can slowly pick up after a shock. That's how it seems to work in the world, but sticky prices do not deliver that result. Hence, the real interest rate doesn't change at all in response to this persistent rise in nominal interest rates.  Now maybe inflation is sticky, costs apply to the derivative not the level, but absolutely none of the immense literature on price stickiness considers that possibility or how in the world it might be true, at least as far as I know. Let me know if I'm wrong. At a minimum, I hope I have started to undermine your faith that we all have easy textbook models in which higher interest rates reliably lower inflation. (Yes, the shock is negative. Look at the Taylor rule. This happens a lot in these models, another reason you might worry. The shock can go in a different direction from observed interest rates.) Panel 3 lowers the persistence of the shock to a cleverly chosen 0.75. Now (with sigma=1, kappa=0.1, phi= 1.2), inflation now moves with no change in interest rate at all.  The Fed merely announces the shock and inflation jumps all on its own. I call this "equilibrium selection policy" or "open mouth policy." You can regard this as a feature or a bug. If you believe this model, the Fed can move inflation just by making speeches! You can regard this as powerful "forward guidance." Or you can regard it as nuts. In any case, if you thought that the Fed's mechanism for lowering inflation is to raise nominal interest rates, inflation is sticky, real rates rise, output falls and inflation falls, well here is another case in which the standard model says something else entirely. Panel 4 is of course my main hobby horse these days. I tee up the question in Panel 1 with the red line. In that panel, the nominal interest are is higher than the expected inflation rate. The real interest rate is positive. The costs of servicing the debt have risen. That's a serious effect nowadays. With 100% debt/GDP each 1% higher real rate is 1% of GDP more deficit, $250 billion dollars per year. Somebody has to pay that sooner or later. This "monetary policy" comes with a fiscal tightening. You'll see that in the footnotes of good new-Keynesian models: lump sum taxes come along to pay higher interest costs on the debt. Now imagine Jay Powell comes knocking to Congress in the middle of a knock-down drag-out fight over spending and the debt limit, and says "oh, we're going to raise rates 4 percentage points. We need you to raise taxes or cut spending by $1 trillion to pay those extra interest costs on the debt." A laugh might be the polite answer. So, in the last graph, I ask, what happens if the Fed raises interest rates and fiscal policy refuses to raise taxes or cut spending? In the new-Keynesian model there is not a 1-1 mapping between the shock (u) process and interest rates. Many different u produce the same i. So, I ask the model, "choose a u process that produces exactly the same interest rate as in the top left panel,  but needs no additional fiscal surpluses." Declines in interest costs of the debt (inflation above interest rates) and devaluation of debt by period 1 inflation must match rises in interest costs on the debt (inflation below interest rates). The bottom right panel gives the answer to this question. Review: Same interest rate, no fiscal help? Inflation rises. In this very standard new-Keynesian model,  higher interest rates without a concurrent fiscal tightening raise inflation, immediately and persistently. Fans will know of the long-term debt extension that solves this problem, and I've plugged that solution before (see the "Expectations" paper above).The point today: The statement that we have easy simple well understood textbook models, that capture the standard intuition -- higher nominal rates with sticky prices mean higher real rates, those lower output and lower inflation -- is simply not true. The standard model behaves very differently than you think it does. It's amazing how after 30 years of playing with these simple equations, verbal intuition and the equations remain so far apart. The last two bullet points emphasize two other aspects of the intuition vs model separation. Notice that even in the top left graph, higher interest rates (and lower output) come with rising inflation. At best the higher rate causes a sudden jump down in inflation -- prices, not inflation, are sticky even in the top left graph -- but then inflation steadily rises. Not even in the top left graph do higher rates send future inflation lower than current inflation. Widespread intuition goes the other way. In all this theorizing, the Phillips Curve strikes me as the weak link. The Fed and common intuition make the Phillips Curve causal: higher rates cause lower output cause lower inflation. The original Phillips Curve was just a correlation, and Lucas 1972 thought of causality the other way: higher inflation fools people temporarily to producing more.  Here is the Phillips curve (unemployment x axis, inflation y axis) from 2012 through last month. The dots on the lower branch are the pre-covid curve, "flat" as common wisdom proclaimed. Inflation was still 2% with unemployment 3.5% on the eve of the pandemic. The upper branch is the more recent experience. I think this plot makes some sense of the Fed's colossal failure to see inflation coming, or to perceive it once the dragon was inside the outer wall and breathing fire at the inner gate. If you believe in a Phillips Curve, causal from unemployment (or "labor market conditions") to inflation, and you last saw 3.5% unemployment with 2% inflation in February 2021, the 6% unemployment of March 2021 is going to make you totally ignore any inflation blips that come along. Surely, until we get well past 3.5% unemployment again, there's nothing to worry about. Well, that was wrong. The curve "shifted" if there is a curve at all. But what to put in its place? Good question. Update:Lots of commenters and correspondents want other Phillips Curves. I've been influenced by a number of papers, especially "New Pricing Models, Same Old Phillips Curves?" by Adrien Auclert, Rodolfo Rigato, Matthew Rognlie, and Ludwig Straub, and "Price Rigidity: Microeconomic Evidence and Macroeconomic Implications" by Emi Nakamura and  Jón Steinsson, that lots of different micro foundations all end up looking about the same. Both are great papers. Adding lags seems easy, but it's not that simple unless you overturn the forward looking eigenvalues of the system; "Expectations and the neutrality of interest rates" goes on in that way. Adding a lag without changing the system eigenvalue doesn't work. 

This applies both to that archaic idea of precise Keynesian demand management and also the more recent Modern Monetary Theory. They don't work because: Official figures have confirmed the UK economy went into recession at the end of last year, after the latest estimate found it had contracted in the last two quarters of 2023.In a blow to the government's economic standing, the Office for National Statistics (ONS) said the economy, measured by gross domestic product (GDP) shrank by 0.3% in the last three months of the year, unrevised from an earlier estimate.That archaic Keynesianism would suggest that back this time last year - about - the government should have increased the deficit. Spent more - easy enough - or reduced taxation - Hah! - in order to use fiscal policy to boost the economy. MMT has a slightly different prescription, keep printing money until the economy runs hot then tax back the excess money creation causing any inflation. We've now the reliable figures giving us the policy we should have followed a year after whatever it is we should have done. That means that the GDP figures cannot be used as a guide to policy, obviously - we've not a time machine to go back and change policy now that we know, do we? Hayek wins again that is. We simply do not gather information in time and in detail sufficient to be able to manage the economy in any detail. Yes, obviously, 10% changes in GDP - in either direction - mean action should be taken and we'd have other guides to that happening other than these GDP figures too. But given that Hayek does win again we've simply not the information flow to be able to follow that dream of that detailed macroeconomic management. This leaves us with getting the microeconomics right - incentives and so on - and then seeing what happens. Which is, as we've long said, about the only form of economic planning we can do that actually works.

John Cochrane's blog has always been a favorite of mine. It's provocative. It's entertaining. And it invariably leads me to reflect on a variety of notions I have floating around in my head. In his latest piece,  he asks an interesting question: How does the Fed come up with its inflation forecast? What sort of model might be embedded in the minds of FOMC members? I like the question and the thought experiment. My comments below should not be construed as criticism. Think of them more as thoughts that come to mind in a conversation. (It's more fun to do this in public than in private.)John begins with the observation that while the Fed evidently expects inflation to decline as the Fed's policy rate is increased, at no point in the transition dynamic back to 2% inflation is the real rate of interest very high. To quote John (italics in original): the Fed believes inflation will almost entirely disappear all on its own, without the need for any period of high real interest rates. Of course, this is in sharp contrast with the Volcker disinflation, an episode that demonstrated, in the minds of many, how a persistently high real rate of interest was needed to make inflation go down (some push back in this paper here).John believes that the current inflation was generated in large part by a big fiscal shock in the form of a money transfer (an increased in USTs unsupported by the prospect of higher future taxes). I'm inclined to agree with this view, though surely there other factors playing a role (see here). John asks how this type of shock can be expected to generate a transitory inflation with the real interest rate kept (say) negative throughout the entire transition dynamic. Below, I offer a simple model that rationalizes this expectation. Whether it's the model FOMC members have in their heads, I'm not sure. (Well, I happen to know in the case of two FOMC members, but I won't share this here.)Formally, I have in mind a simple OLG model (see, here). The model is Non-Ricardian (the supply of government debt is viewed as private wealth). The model's properties are more Old Keynesian than New Keynesian. The model is also consistent with Monetarism, except with the supply of base money replaced with the supply of outside assets (i.e., all government securities--cash, reserves, bills, notes and bonds). So, I'm thinking about my model beginning in an hypothetical stationary state. The real economy is growing at some constant rate (say, zero). The supply of outside assets consists of zero interest securities (monetary policy is pegging the nominal interest rate to zero all along the yield curve). This supply of "debt" is also growing at some constant rate. Debt is never repaid--it is rolled over forever. Indeed, the nominal supply of debt is growing forever. New debt is used to finance government spending. The real primary budget deficit is held constant. The government is running a perpetual budget deficit via bond seigniorage; see here. The steady-state inflation rate in this economy is given by the rate of growth of the supply of nominal outside assets. (It is also possible that the inflation rate is determined by shifts in the demand for USTs; see here, for example). The real interest rate (on money) is negative. OK, now let's consider a large fiscal shock in the form of a one-time increase in the supply of outside assets (i.e., a helicopter drop of money that is never reversed).  The effect of this shock is to induce a transitory inflation (a permanent increase in the price-level). An increase in the nominal supply of money at a given interest rate at full employment makes the cost of living go up -- it makes the real debt go down. And oh, by the way, the debt-to-GDP ratio is declining thanks in part to inflation:This is despite the persistent negative real interest rate prevailing in the economy. I mean, what else might one imagine from a one-time injection of money? Is this is what the Fed is thinking? (This is what I'm thinking!) Note: an increase in the interest rate in this model would unleash a disinflationary force, but this would only serve to speed up the transition dynamic. As it turns out, this simple story seems consistent with what I take to be John's preferred theory of inflation. The large fiscal shock here is unaccompanied by the prospect of future primary budget surpluses. The effect is to increase the price level (i.e., a temporary inflation). Maybe the Fed has John's FTPL model in mind? Neither of these stories line up particularly well with the New Keynesian model, which emphasizes interest rate policy as *the* way inflation is controlled. There are, however, many strange things going on in this model. First, while no explicit attention is paid to fiscal policy, the fiscal regime plays a critical role in determining model dynamics (basic assumption is lump-sum taxes and Ricardian fiscal regime). Second, the Taylor principle that is needed to determine a locally unique rational expectations equilibrium is an off-equilibrium credible threat to basically blow the economy up if individuals do not coordinate on the proposed equilibrium (I learned this from John here.)  By the way, Peter Howitt provides a different (and in my view, a more compelling) explanation for the "Taylor principle" here--published a year before Taylor 1993. Given these shortcomings, why are we even using this model as a benchmark? This is another good question. John presumably picks this model because he sees no better alternative for modeling monetary policy via an interest rate rule. If he wants an alternative, he can read my paper above. Or, he can appeal to his own class of models extended to permit a liquidity function for USTs. These models easily accommodate stable inflation at negative real rates of interest. But whether this is how FOMC members organize their thinking, I'm not sure.In any case, John picks an off-the-shelf NK model and assumes that it adequately captures what is in the mind of many FOMC members. Let's see what he does next (Modeling the Fed). He writes: "The Fed clearly believes that once a shock is over, inflation stops, even if the Fed does not do much to nominal interest rates. This is the "Fisherian" property. It is not the property of traditional models. In those models, once inflation starts, it will spiral out of control unless the Fed promptly raises interest rates." [I think he meant "threatens to raise interest rates.]Comment 1: I'm not sure what he means by a "Fisherian" property. (Note: the Fisher equation holds in the OLG model I cited above--though the real rate of interest is not generally fixed in those settings.) Comment 2: Conventional models? I presume he means Woodford's basic NK model. It seems likely to me, however, that FOMC members may have other "conventional" models in their heads -- like the Old Keynesian model or the Old Monetarist model--both of which continue to be taught as standard fare in undergraduate curricula.  OK, so John considers a very basic IS-PC model and considers two alternative hypotheses for how inflation expectations are determined. The first hypothesis is a simple adaptive rule (see also Howitt's work above). The second hypothesis is perfect foresight (rational expectations) -- which, by the way, implicitly embeds knowledge of the Ricardian fiscal regime. Under the adaptive expectations model, inflation explodes. Under the rational expectations hypothesis, inflation largely follows the Fed's actual forecast. Maybe this is what the Fed is thinking? The Fed has rational expectations? Except that I'm not really sure what this means. John does give us a further hint though. He goes on to say "Not only is the Fed rational expectations, neo-Fisherian, it seems to believe that prices are surprisingly flexible!" Right. So the Neo-Fisherian hypothesis is that to get a permanently lower rate of inflation, the Fed must (at least eventually) lower its policy rate (and vice versa to raise the rate of inflation). I've questioned this hypothesis in the past (see here). But what's going on here now? Is John suggesting that the FOMC is made up of closet Neo-Fisherians? Steve Williamson would no doubt be pleasantly surprised. John writes: "The proposition that once the shock is over inflation will go away on its own may not seem so radical. Put that way, I think it does capture what's on the Fed's mind. But it comes inextricably with the very uncomfortable Fisherian implication. If inflation converges to interest rates on its own, then higher interest rates eventually raise inflation, and vice-versa." No, I'm afraid the conclusion that inflation is transitory (even with negative real rates) is NOT inextricably linked to the Neo-Fisherian proposition. It is only inextricably linked this way in a class of economic models that: [1] are pretty bad; and [2] highly unlikely to be in the heads of most FOMC members.