Macroeconomists have largely converged on method, model design, reduced-form shocks, and principles of policy advice. Our main disagreements today are about implementing the methodology. Some think New Keynesian models are ready to be used for quarter-to-quarter quantitative policy advice; we do not. Focusing on the state-of-the-art version of these models, we argue that some of its shocks and other features are not structural or consistent with microeconomic evidence. Since an accurate structural model is essential to reliably evaluate the effects of policies, we conclude that New Keynesian models are not yet useful for policy analysis.

A model of a labor market is developed in which agents possess private information about their marginal products. As a result, involuntary unemployment may arise as a consequence of attempts by firms to create appropriate self-selection incentives. Moreover, employment lotteries may arise for the same reason despite the fact that, in equilibrium, there is no uncertainty in the model. When employment is random, this is both privately and socially desirable. Finally, it is shown that the unemployment that arises is consistent with (a) pro-cyclical aggregate real wages and productivity, (b) employment that fluctuates (at individual and aggregate levels) much more than real wages.

An overlapping generations model is developed that contains labor markets in which adverse selection problems arise. As a response to these problems, quantity rationing of labor occurs. In addition, the model is capable of generating (a) random employment and prices despite the absence of underlying uncertainty in equilibrium; (b) a statistical (nondegenerate) Phillips curve; (c) procyclical movements in productivity; (d) correlations between aggregate demand and unemployment (and output); (e) an absence of correlation between unemployment (employment) and real wages. In addition, the Phillips curve obtained typically has the "correct" slope. Finally, the model reconciles the theoretical importance and observed unimportance of intertemporal substitution effects, and explains why price level stability may be a poor policy objective.

We propose a simple method to help researchers develop quantitative models of economic fluctuations. The method rests on the insight that many models are equivalent to a prototype growth model with time-varying wedges which resemble productivity, labor and investment taxes, and government consumption. Wedges corresponding to these variables—efficiency, labor, investment, and government consumption wedges—are measured and then fed back into the model in order to assess the fraction of various fluctuations they account for. Applying this method to U.S. data for the Great Depression and the 1982 recession reveals that the efficiency and labor wedges together account for essentially all of the fluctuations; the investment wedge plays a decidedly tertiary role, and the government consumption wedge, none. Analyses of the entire postwar period and alternative model specifications support these results. Models with frictions manifested primarily as investment wedges are thus not promising for the study of business cycles. (See Additional Material for a response to Christiano and Davis (2006).)

This paper proposes a simple method for guiding researchers in developing quantitative models of economic fluctuations. We show that a large class of models, including models with various frictions, are equivalent to a prototype growth model with time-varying wedges that, at least at face value, look like time-varying productivity, labor taxes, and capital income taxes. We label the time-varying wedges as efficiency wedges, labor wedges, and investment wedges. We use data to measure these wedges and then feed them back into the prototype growth model. We then assess the fraction of fluctuations accounted for by these wedges during the great depressions of the 1930s in the United States, Germany, and Canada. We find that the efficiency and labor wedges in combination account for essentially all of the declines and subsequent recoveries. Investment wedges play, at best, a minor role.

It is commonly asserted that with excess plant capacity, expansive policy stimulates output and lowers unemployment without substantially boosting inflation, while at full capacity most of the impact is on inflation. This assertion is critically examined. First, two common definitions of capacity--engineering and economic—are examined and found to be nebulous. The concepts of supply and demand are older, but better. Full capacity is reinterpreted as points where the supply curve is steep and excess capacity as points where it is fairly flat. Then the "Keynesian" model in which stimulative policy shifts only the demand curve is compared to the "classical" model where stimulative policy shifts both demand and supply curves. For the former model the assertion on capacity utilization is correct, while in the latter it is not. Empirical tests are performed to determine whether measured capacity utilization is useful for predicting inflation. The tests are ambiguous, but certainly do not strongly favor capacity utilization.

Between 2007 and 2013, U.S. households experienced a large and persistent decline in net worth. The objective of this paper is to study the business cycle implications of such a decline. We first develop a tractable monetary model in which households face idiosyncratic unemployment risk that they can partially self-insure using savings. A low level of liquid household wealth opens the door to self-fullfilling fluctuations: if wealth-poor households expect high unemployment, they have a strong precautionary incentive to cut spending, which can make the expectation of high unemployment a reality. Monetary policy, because of the zero lower bound, cannot rule out such expectations-driven recessions. In contrast, when wealth is sufficiently high, an aggressive monetary policy can keep the economy at full employment. Finally, we document that during the U.S. Great Recession wealth-poor households increased saving more sharply than richer households, pointing towards the importance of the precautionary channel over this period.

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