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Frontmatter -- CONTENTS -- FIGURES -- TABLES -- PREFACE -- ACKNOWLEDGMENTS -- ORGANIZATION OF THIS BOOK -- Part I. Preliminaries -- Chapter 1. Questions about Questions -- Chapter 2. The Experimental Ideal -- Part II. The Core -- Chapter 3. Making Regression Make Sense -- Chapter 4. Instrumental Variables in Action: Sometimes You Get What You Need -- Chapter 5. Parallel Worlds: Fixed Effects, Differences-in-Differences, and Panel Data -- Part III. Extensions -- Chapter 6. Getting a Little Jumpy: Regression Discontinuity Designs -- Chapter 7. Quantile Regression -- Chapter 8. Nonstandard Standard Error Issues -- LAST WORDS -- ACRONYMS AND ABBREVIATIONS -- EMPIRICAL STUDIES INDEX -- REFERENCES -- INDEX

Macroeconomists have long been concerned with the causal effects of monetary policy. When the identification of causal effects is based on a selection-on-observables assumption, non-causality amounts to the conditional independence of outcomes and policy changes. This paper develops a semiparametric test for conditional independence in time series models linking a multinomial policy variable with unobserved potential outcomes. Our approach to conditional independence testing is motivated by earlier parametric tests, as in Romer and Romer (1989, 1994, 2004). The procedure developed here is semiparametric in the sense that we model the process determining the distribution of treatment - the policy propensity score - but leave the model for outcomes unspecified. A conceptual innovation is that we adapt the cross-sectional potential outcomes framework to a time series setting. This leads to a generalized definition of Sims (1980) causality. A technical contribution is the development of root-T consistent distribution-free inference methods for full conditional independence testing, appropriate for dependent data and allowing for first-step estimation of the propensity score. -- Monetary policy ; propensity score ; multinomial treatments ; causality

"This paper uses the 2000 Census 1-in-6 sample to look at the long-term impact of Vietnam-era military service. Instrumental Variables estimates using draft-lottery instruments show post-service earnings losses close to zero in 2000, in contrast with earlier results showing substantial earnings losses for white veterans in the 1970s and 1980s. The estimates also point to a marked increase in schooling that appears to be attributable to the Vietnam-era GI Bill. The net wage effects observed in the 2000 data can be explained by a flattening of the experience profile in middle age and a modest return to the increased schooling generated by the GI Bill. Evidence on disability effects is mixed but seems inconsistent with a long-term effect of Vietnam-era military service on health"--National Bureau of Economic Research web site

Natural and agricultural resources for which there is a substantial black market, such as coca, opium, and diamonds, appear especially likely to be exploited by the parties to a civil conflict. Even legally traded commodities such as oil and timber have been linked to civil war. On the other hand, these resources may also provide one of the few reliable sources of income in the countryside. In this paper, we study the economic and social consequences of a major exogenous shift in the production of one such resource coca paste into Colombia, where most coca leaf is now harvested. Our analysis shows that this shift generated only modest economic gains in rural areas, primarily in the form of increased self-employment earnings and increased labor supply by teenage boys. The results also suggest that the rural areas which saw accelerated coca production subsequently became more violent, while urban areas were affected little. The acceleration in violence is greater in departments (provinces) where there was a pre-coca guerilla presence. Taken together, these findings are consistent with the view that the Colombian civil conflict is fueled by the financial opportunities that coca provides, and that the consequent rent-seeking activity by combatants limits the economic gains from coca cultivation.

Macroeconomists have long been concerned with the causal effects of monetary policy. When the identification of causal effects is based on a selection-on-observables assumption, non-causality amounts to the conditional independence of outcomes and policy changes. This paper develops a semiparametric test for conditional independence in time series models linking a multinomial policy variable with unobserved potential outcomes. Our approach to conditional independence testing is motivated by earlier parametric tests, as in Romer and Romer (1989, 1994, 2004). The procedure developed here is semiparametric in the sense that we model the process determining the distribution of treatment - the policy propensity score - but leave the model for outcomes unspecified. A conceptual innovation is that we adapt the cross-sectional potential outcomes framework to a time series setting. This leads to a generalized definition of Sims (1980) causality. A technical contribution is the development of root-T consistent distribution-free inference methods for full conditional independence testing, appropriate for dependent data and allowing for first-step estimation of the propensity score.

Military service reduces civilian labor market experience but subsidizes higher education through the GI Bill. Both of these channels are likely to affect civilian earnings. New estimates of the effects of military service using Vietnam-era draft-lottery instruments show post-service earnings effects close to zero in 2000, in contrast with earlier results showing substantial earnings losses for white Vietnam veterans in the 1970s and 1980s. The recent estimates also point to a marked increase in post-secondary schooling that appears to be attributable to the Vietnam-era GI Bill. Seen through the lens of a Mincer wage equation, the wage effects observed in 2000 data can be explained by a flattening of the experience profile in middle age and a modest return to the additional schooling funded by the GI Bill. In particular, IV estimates of the returns to GI Bill-funded schooling are well below OLS estimates. Wage equations that allow for nonlinearities in the returns to schooling and a possible negative effect of military service on health, leave the main findings unchanged.

Natural and agricultural resources for which there is a substantial black market, such as coca, opium, and diamonds, appear especially likely to be exploited by the parties to a civil conflict. Even legally traded commodities such as oil and timber have been linked to civil war. On the other hand, these resources may also provide one of the few reliable sources of income in the countryside. In this paper, we study the economic and social consequences of a major exogenous shift in the production of one such resource coca paste into Colombia, where most coca leaf is now harvested. Our analysis shows that this shift generated only modest economic gains in rural areas, primarily in the form of increased self-employment earnings and increased labor supply by teenage boys. The results also suggest that the rural areas which saw accelerated coca production subsequently became more violent, while urban areas were affected little. The acceleration in violence is greater in departments (provinces) where there was a pre-coca guerilla presence. Taken together, these findings are consistent with the view that the Colombian civil conflict is fueled by the financial opportunities that coca provides, and that the consequent rent-seeking activity by combatants limits the economic gains from coca cultivation.

Abstract
Reduced labour market flexibility may protect some native workers from immigrant competition but can increase negative effects on equilibrium employment. This motivates an analysis of immigration effects interacted with institutions. OLS estimates for European countries show small, mostly negative immigration effects while an IV strategy based on immigrants from former Yugoslavia generates larger though mostly insignificant negative estimates. Specifications allowing interactions between immigration and measures of labour and product market rigidity are consistent with the view that reduced flexibility increases negative immigration effects. The estimates typically imply more native job losses in countries with restrictive institutions, especially restricted product markets.