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"We show that deviations from long-run stability of product prices are optimal in the presence of endogenous producer entry and product variety in a sticky-price model with monopolistic competition in which price stability would be optimal in the absence of entry. Specifically, a long-run positive (negative) rate of inflation is optimal when the benefit of variety to consumers falls short of (exceeds) the market incentives for creating that variety under flexible prices, governed by the desired markup. Plausible preference specifications and parameter values justify a long-run inflation rate of two percent or higher. Price indexation implies even larger deviations from long-run price stability. However, price stability (around this non-zero trend) is close to optimal in the short run, even in the presence of time-varying flexible-price markups that distort the allocation of resources across time and states. The central bank uses its leverage over real activity in the long run, but not in the short run. Our results point to the need for continued empirical research on the determinants of markups and investigation of the benefit of product variety to consumers"--National Bureau of Economic Research web site

This paper studies the role of endogenous producer entry and product creation for monetary policy analysis and business cycle dynamics in a general equilibrium model with imperfect price adjustment. Optimal monetary policy stabilizes product prices, but lets the consumer price index vary to accommodate changes in the number of available products. The free entry condition links the price of equity (the value of products) with marginal cost and markups, and hence with inflation dynamics. No-arbitrage between bonds and equity links the expected return on shares, and thus the financing of product creation, with the return on bonds, affected by monetary policy via interest rate setting. This new channel of monetary policy transmission through asset prices restores the Taylor Principle in the presence of capital accumulation (in the form of new production lines) and forward-looking interest rate setting, unlike in models with traditional physical capital. We also study the implications of endogenous variety for the New Keynesian Phillips curve and business cycle dynamics more generally, and we document the effects of technology, deregulation, and monetary policy shocks, as well as the second moment properties of our model, by means of numerical examples.

International audience ; A liquidity-insurance motive for monetary policy operates when heterogeneous households use government-provided liquidity ("money") to insure idiosyncratic risk. In our tractable sticky-price model this changes the central bank's trade-off by adding a linear benefit of insurance in the second-order approximation to aggregate welfare. Inflation volatility hinders the consumption volatility of constrained households as a side-effect of liquidity-insuring them; but price stability has quantitatively significant welfare costs only when monopolistic rents are also large, which indicates a complementarity between imperfect-insurance and New-Keynesian distortions. Helicopter drops are welfare-superior to open-market operations to achieve insurance, but quantitatively their benefit is surprisingly small.

International audience ; A liquidity-insurance motive for monetary policy operates when heterogeneous households use government-provided liquidity ("money") to insure idiosyncratic risk. In our tractable sticky-price model this changes the central bank's trade-off by adding a linear benefit of insurance in the second-order approximation to aggregate welfare. Inflation volatility hinders the consumption volatility of constrained households as a side-effect of liquidity-insuring them; but price stability has quantitatively significant welfare costs only when monopolistic rents are also large, which indicates a complementarity between imperfect-insurance and New-Keynesian distortions. Helicopter drops are welfare-superior to open-market operations to achieve insurance, but quantitatively their benefit is surprisingly small.

Forthcoming, Journal of Economic Dynamics and Control International audience Recent estimates of the output Euler equation for the United States indicate that the elasticity of aggregate demand to interest rates is not significantly different from zero. We first argue that this result may hide a structural break: the estimated elasticity is a convolution of two coefficients with opposite signs across the samples 1965-1979 and 1982-2003. The sign of the coefficient in the earlier sample is inconsistent with standard economic theory and intuition. We outline a model with limited asset markets participation that can generate this change in sign when asset market participation changes from low to high, and provide institutional evidence for such a change in the United States in the late 70s and early 80s.