We develop a life-cycle model of the labor market in which different worker-firm matches have different quality and the assignment of the right workers to the right firms is time consuming because of search and learning frictions. The rate at which workers move between unemployment, employment...

When limited commitment hinders unsecured credit, assets help by serving as collateral. We study models where assets differ in pledgability - the extent to which they can be used to secure loans - and hence liquidity. Although many previous analyses of imperfect credit focus on producers, we...

Shimer's calibrated version of the Mortensen-Pissarides model generates unemployment fluctuates much smaller than the data. Hagedorn and Manovskii present an alternative calibration that yields fluctuations consistent with the data, but this has been challenged by Costain and Reiter, who say it...

We study bilateral exchange, both direct trade and indirect trade that happens through chains of intermediaries or middlemen. We develop a model of this activity and present applications. This illustrates how, and how many, intermediaries get involved, and how the terms of trade are determined....

Why do some sellers set nominal prices that apparently do not respond to changes in the aggregate price level? In many models, prices are sticky by assumption; here it is a result. We use search theory, with two consequences: prices are set in dollars, since money is the medium of exchange; and...

The generation and implementation of ideas, or knowledge, is crucial for economic performance. We study this process in a model of endogenous growth with frictions. Productivity increases with knowledge, which advances via innovation, and with the exchange of ideas from those who generate them...

We study models of credit with limited commitment, which implies endogenous borrowing constraints. We show that there are multiple stationary equilibria, as well as nonstationary equilibria, including some that display deterministic cyclic and chaotic dynamics. There are also stochastic...

We extend the concept of competitive search equilibrium to environments with private information, and in particular adverse selection. Principals (e.g. employers or agents who want to buy assets) post contracts, which we model as revelation mechanisms. Agents (e.g. workers, or asset holders)...

We survey search-theoretic models of the labor market and discuss their usefulness for analyzing labor market dynamics, job turnover, and wages. We first examine single-agent models, showing how they can incorporate many interesting features and generate rich predictions. We then consider...

We study the long-run relation between money, measured by inflation or interest rates, and unemployment. We first discuss data, documenting a strong positive relation between the variables at low frequencies. We then develop a framework where both money and unemployment are modeled using...