This paper argues that the textbook search and matching model cannot generate the observed business-cycle-frequency fluctuations in unemployment and job vacancies in response to shocks of a plausible magnitude. In the United States, the standard deviation of the vacancy-unemployment ratio is almost 20 times as large as the standard deviation of average labor productivity, while the search model predicts that the two variables should have nearly the same volatility. 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 (unemploymentvacancy locus). A shock to the separation rate generates a counterfactually positive correlation between unemployment and vacancies. In both cases, the model exhibits virtually no propagation.

This paper studies the assignment of heterogeneous workers to heterogeneous jobs. Owing to the anonymity of a large labor market, workers use mixed strategies when applying for jobs. This randomness generates coordination frictions. Two workers may apply for a particular job, whereas an identical job gets no applications. The model generates assortative matching, with a positive but imperfect correlation between matched workers’ and firms’ types. It predicts that a worker’s wage is increasing in her job’s productivity and a firm’s profit is increasing in its employees’ productivity. The model also yields a version of the welfare theorems.

We survey the literature on search-theoretic models of the labor market. We show how this approach addresses many issues, including the following: Why do workers sometimes choose to remain unemployed? What determines the lengths of employment and unemployment spells? How can there simultaneously exist unemployed workers and unfilled vacancies? What determines aggregate unemployment and vacancies? How can homogeneous workers earn different wages? What are the tradeoffs firms face from different wages? How do wages and turnover interact? What determines efficient turnover? We discuss various modeling choices concerning wage determination and the meeting process, including recent models of directed search.