This paper assesses how various approaches to modelling the separation margin a¤ect the ability of the Mortensen-Pissarides job matching model to explain key facts about the aggregate labor market. Allowing for realistic time variation in the separation rate, whether exogenous or endogenous, greatly in- creases the unemployment variability generated by the model. Speci…cations with exogenous separation rates, whether constant or time-varying, fail to pro- duce realistic volatility and productivity responsiveness of the separation rate and worker ‡ows. Speci…cations with endogenous separation rates, on the other hand, succeed along these dimensions. In addition, the endogenous separation model with on-the-job search yields a realistic Beveridge curve correlation, and it performs well in accounting for the productivity responsiveness of vacancies and market tightness. When the Hagedorn-Manovskii calibration approach is used, the behavior of the job …nding rate, vacancies and market tightness be- comes more realistic, but the volume of job-to-job transitions in the on-the-job search speci…cation is essentially zero.

We study the cyclical behavior of job loss and hiring using CPS worker flow data, adjusted for margin error and time aggregation error. The band pass filter is used to isolate cyclical components. We consider both total worker flows and transition hazard rates within a unified framework. Our results provide overwhelming support for a "separation-driven" view of employment adjustment whereby total job loss and hiring rise sharply during economic downturns, initiated by increases in job loss hazard rate. Worker flows and transition hazard rates are highly volatile at business cycle frequencies. These patterns are especially strong among prime-age workers. For young workers, job loss and hiring adjust procyclically due to movements into and out of the labor force.

This paper analyzes the role of third party intermediaries, such as courts and arbitrators, in contract enforcement. In our model, intermediaries compel contracted transfers and resolve disputes when requested to do so by the contracting agents. When the verifiability of information is limited, successful enforcement requires that dispute resolution costs be sufficiently great. Optimal enforcement systems economize on dispute resolution and information costs, and may involve establishment of specific systems tailored to particular groups. We show further that the "holdup problem" may be resolved via an appropriately designed dispute resolution sytem.

We propose a theory of contracting in long-term relationships, emphasizing the role of social institutions in conditioning players' joint selection of equilibria. Players adopt a social conditioning system in order to place boundaries on their recurrent negotiation and thereby sustain a desirable joint selection of equilibrium. Social conventions have value because players cannot freely reinterpret the labels attached to histories, in contrast to labels that the players might assign internally. We present examples of social conventions that are useful for sustaining cooperative interaction. Our model combines an explicit bargaining technology with a renegotiation concept, coherent equilibrium, that builds on internal consistency. Coherent equilibria exist in general and, for an important class of games, induce unique outcomes.

In the U.S. labor maarket, the vacancy-unemployment ratio and unemployment react sluggishly to productivity shocks. We show that the job matching model in its standard form cannot reproduce these patterns due to excessively rapid vacancy responses. Extending the model to incorprate sunk costs for vacancy creation yields highly realistic dynamics. Creation costs induce entrant firms to smooth the adjustment of new openings following a shock, leading the stock of vacancies to react sluggishly.

In aggregate U.S. data, exogenous shocks to labor productivity induce highly persistent and hump-shaped responses to both the vacancy-unemployment ratio and employment. We show that the standard version of the Mortensen-Pissarides matching model fails to replicate this dynamic pattern due to the rapid responses of vacancies. We extend the model by introducing a sunk cost for creating new job positions, motivated by the well-known fact that worker turnover exceeds job turnover. In the matching model with sunk costs, vacancies react sluggishly to shocks, leading to highly realistic dynamics.

A striking implication of the replacement of adaptive expectations by Rational Expectations was the "Lucas Critique," which showed that expectation parameters, and endogenous variable dynamics, depend on policy parameters. We reconsider this issue from the vantage point of bounded rationality. Adaptive expectations, with an optimally tuned parameter, can provide a reasonable, if not fully rational, forecast method when the true process is unknown. We show that for a range of processes, monetary policy remains subject to the Lucas critique. However, there are also regimes in which the expectation parameter is locally invariant and the Lucas critique does not apply.

This paper applies regime switching methods to the problem of measuring monetary policy. Policy preferences and structural factors are specified parametrically as independent Markov processes. Interaction between the structural and preference parameters in the policy rule serves to identify the two processes. The estimates uncover policy episodes that are initiated by switches of "dove regimes," shown to Granger cause both NBER recessions and the Romer dates. These episodes imply real effects of monetary policy that are smaller than those found in previous studies.

This paper presents a theory of dynamic trade agreements in which external institutions, such as the WTO, play a central role in supporting credible enforcement. In our model, countries engage in ongoing negotiations, and as a consequence cooperative agreements become unsustainable in the absence of external enforcement institutions. By using mechanisms such as delays in dispute resolution and direct penalties, enforcement institutions can restore incentives for cooperation, despite the lack of any coercive power. The occurrence of costly trade disputes, and the feasibility of mechanisms such as escape clauses, depend on the adaptability of enforcement institutions in their use of information.

We employ a comprehensive matched employer-employee data set for Brazil to analyze wage determinants and compare results to Abowd, Kramarz, Margolis and Troske (2001) for French and U.S. manufacturing. Returns to education and experience in Brazilian manufacturing exceed those of the other countries, while occupation differentials are similar. The gender differential in Brazilian and U.S. manufacturing coincides, and is considerably smaller than in France. Estimates are unaffected by selectivity of Brazilian workers into formal employment. The links between firm performance and wage components in Brazil resemble those of France. Worker characteristics have comparable explanatory power for manufacturing wage variability in the three countries but establishment-fixed effects explain relatively less of the Brazilian wage variation. Despite the inclusion of establishment effects, regressors predict at most sixty percent of wage variability in any Brazilian sector, suggesting that explanations for earnings variability ought to focus on worker characteristics, not establishment wage policies.