There are two facts about the world that we take as given: First the "law of one price" is false -- one can find many different prices for what appears to be, beyond reasonable doubt, the same good. Second, prices are set in nominal terms and appear, beyond reasonable doubt, to be sticky -- some...

We extend the notion of competitive search equilibrium to an environment with adverse selection. Uninformed principals post contracts to attract informed agents. Agents observe the contracts and apply for one, trading off the probability of matching with a principal against the terms of trade...

Arguably the most difficult question in macroeconomics is: why do individuals set prices in nominal terms that do not respond to changes in the aggregate price level? Of course some must respond, or the aggregate does not change, but many prices seem sticky in the short run. In popular macro...

We study the long run (low frequency) dynamic relationship between money, as measured by inflation or interest rates, and unemployment. We first discuss the data. We then develop a framework where money and unemployment are both modeled with microfoundations based on explicit frictions. This...

This paper models the role of assets in facilitating intertemporal exchange: because limited commitment precludes unsecured credit, buyers need to pledge assets as collateral. We develop a general equilibrium model where assets differ in terms of pledgability, and put it to work in applications...

We study economies where houses, in addition to providing utility as shelter, may also facilitate credit transactions, since home equity can be used as collateral. We document there were big increases in home-equity-backed consumption loans coinciding with the start of the house price boom, and...

reneging on obligations.

parameters optimal; for other parameters, strictly positive rates (inflation above the Friedman Rule) are optimal.

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 study economies with an essential role for liquid assets in transactions. The model can generate multiple stationary equilibria, across which asset prices, market participation, capitalization, output and welfare are positively related. It can also generate a variety of nonstationary...