This paper argues that a broad class of search models cannot generate the observed business-cycle-frequency fluctuations in unemployment and job vacancies in response to shocks of a plausible magnitude. In the U.S., the vacancy-unemployment ratio is 20 times as volatile as average labor productivity, while under weak assumptions, search models predict that the vacancy-unemployment ratio and labor productivity have nearly the same variance. I establish this claim both using analytical comparative statics in a very general deterministic search model and using simulations of a stochastic version of the model. I show that a shock that changes average labor productivity primarily alters the present value of wages, generating only a small movement along a downward sloping Beveridge curve (unemployment-vacancy locus). A shock to the job destruction rate generates a counterfactually positive correlation between unemployment and vacancies. In both cases, the shock is only slightly amplified and the model exhibits virtually no propagation. I reconcile these findings with an existing literature and argue that the source of the model’s failure is lack of wage rigidity, a consequence of the assumption that wages are determined by Nash bargaining. ∗ This is a major revision of ‘Equilibrium Unemployment Fluctuations’. I thank Daron Acemoglu, Olivier

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In this paper, we extend the basic Mortensen-Pissarides search and matching model along two dimensions. First, we allow for ex-ante heterogeneity between workers. Second, two technology shocks, neutral and investment-specific, are the driving forces of the economy. Specifically, we integrate the framework of Krusell, Ohanian, Ríos-Rull, and Violante (2000)- a production function with capital-skill complementarity and two skill-groups- into a business-cycle search and matching model. We calibrate the model extending the approach in Hagedorn and Manovskii (2006) and find that the model accounts well for the cyclical behavior of labor market variables in the aggregate and for each demographic group. We show that the response of unemployment to changes in taxes or unemployment insurance benefits is substantially reduced in the model with worker heterogeneity.

Most central banks perceive a trade-off between stabilizing inflation and stabi-lizing the gap between output and desired output. However, the standard new Keynesian framework implies no such trade-off. In that framework, stabilizing inflation is equivalent to stabilizing the welfare-relevant output gap. In this pa-per, we argue that this property of the new Keynesian framework, which we call the divine coincidence, is due to a special feature of the model: the absence of non trivial real imperfections. We focus on one such real imperfection, namely, real wage rigidities. When the baseline new Keynesian model is extended to allow for real wage rigidities, the divine coincidence disappears, and central banks indeed face a trade-off between stabilizing inflation and stabilizing the welfare-relevant output gap. We show that not only does the extended model have more realistic normative implica-tions, but it also has appealing positive properties. In particular, it provides a natural interpretation for the dynamic inflation–unemployment relation found in the data. JEL Classification: E32, E50

This paper theoretically and empirically documents a puzzle that arises when an RBC economy with a job matching function is used to model unemployment. The standard model can generate sufficiently large cyclical fluctuations in unemployment, or a sufficiently small response of unemployment to labor market policies, but it cannot do both. Variable search and separation, finite UI benefit duration, efficiency wages, and capital all fail to resolve this puzzle. However, either sticky wages or match-specific productivity shocks can improve the model’s performance by making the firm’s flow of surplus more procyclical, which makes hiring more procyclical too.

A number of authors have recently emphasized that the conventional model of unemployment dynamics due to Mortensen and Pissarides has difficulty accounting for the relatively volatile behavior of labor market activity over the business cycle. We address this issue by modifying the MP framework to allow for staggered multiperiod wage contracting. What emerges is a tractable relation for wage dynamics that is a natural generalization of the period-by-period Nash bargaining outcome in the conventional formulation. An interesting side-product is the emergence of spillover effects of average wages on the bargaining process. We then show that a reasonable calibration of the model can account well for the cyclical behavior of wages and labor market activity observed in the data. The spillover effects turn out to be important in this respect.

I study the cyclical behavior of an equilibrium search model with endogenous job creation and destruction and extract from it a wage equation that can be compared with the econometric evidence. Job creation in the model is influenced by wages in new matches. I summarize microeconometric evidence on wages in new matches and show that the key model elasticities are consistent with the evidence. Therefore sticky wages is not the answer to the unemployment volatility puzzle. I discuss some alternative mechanisms that can increase volatility, in particular extensions of the model and alternative driving mechanisms. Jobs in the search and matching model command monopoly rents that are shared between the firm and the worker by a wage contract. The most common wage contract found in the literature is derived from Nash, and yields a wage rate that is a linear combination of the productivity of the match and the worker’s returns from search and nonmarket activities. Pissarides (1985) and Mortensen and Pissarides (1994) have shown that because nonmarket returns are less cyclical than labor productivity, employment in the model exhibits more cyclicality than in a competitive market-clearing model. The question that I address in this paper is the role of wages in the cyclical volatil-ities implied by this model. Shimer (2005a), in an influential paper, has shown that

Standard search and matching models of equilibrium unemployment, once properly calibrated, can generate only a small amount of frictional wage dispersion, i.e., wage differentials among ex-ante similar workers induced purely by search frictions. We derive this result for a specific measure of wage dispersion—the ratio between the average wage and the lowest (reservation) wage paid. We show that in a large class of search and matching models this statistic (the “mean-min ratio”) can be obtained in closed form as a function of observable variables (i.e., the interest rate, the value of leisure, and statistics of labor market turnover). Various independent data sources suggest that actual residual wage dispersion (i.e., inequality among observationally similar workers) exceeds the model’s prediction by a factor of 20. We discuss three extensions of the model (risk aversion, volatile wages during employment, and on-the-job search) and find that, in their simplest versions, they can improve its performance, but only modestly. We conclude that either frictions account for a tiny fraction of residual wage dispersion, or the standard model needs to be augmented to confront the data. In particular, the last generation of models with on-the-job search appears promising.

We develop a utility based model of fluctuations, with nominal rigidities, and unemployment. In doing so, we combine two strands of research: the New Keynesian model with its focus on nominal rigidities, and the Diamond-Mortensen-Pissarides model, with its focus on labor market frictions and unemployment. In developing this model, we proceed in two steps. We first leave nominal rigidities aside. We show that, under a standard utility specification, productivity shocks have no effect on unemployment in the constrained efficient allocation. We then focus on the implications of alternative real wage setting mechanisms for fluctuations in unemployment. We then introduce nominal rigidities in the form of staggered price setting by firms. We derive the relation between inflation and unemployment and discuss how it is influenced by the presence of real wage rigidities. We show the nature of the tradeoff between inflation and unemployment stabilization, and we draw the implications for optimal monetary policy.

We develop and estimate a medium scale macroeconomic model that allows for unemployment and staggered nominal wage contracting. In contrast to most existing quantitative models, employment adjustment is on the extensive margain and the employment of existing workers is efficient. Wage rigidity, however, affects the hiring of new workers. The former is introduced via the staggered Nash bargaing setup of Gertler and Trigari (2006). A robust finding is that the model with wage rigidity provides a better description of the data than does a flexible wage version. Overall, the model fits the data roughly as well as existing quantitative macroeconomic models, such as Smets and Wouters (2007) or Christiano, Eichenbaum and Evans (2005). More work is necessary, however, to ensure a robust identification of the key labor market parameters.