Under mild assumptions, the data indicate that fluctuations in nominal interest rate differentials across currencies are primarily fluctuations in time-varying risk. This finding is an immediate implication of the fact that exchange rates are roughly random walks. If most fluctuations in interest differentials are thought to be driven by monetary policy, then the data call for a theory which explains how changes in monetary policy change risk. Here, we propose such a theory based on a general equilibrium monetary model with an endogenous source of risk variation—a variable degree of asset market segmentation.

Manufacturing plants have a clear life cycle: they are born small, grow substantially with age, and eventually die. Economists have long thought that this life cycle is driven by organization capital, the accumulation of plant‐specific knowledge. The location of plants in the life cycle determines the size of the payments, or organization rents, plant owners receive from organization capital. These payments are compensation for the interest cost to plant owners of waiting for their plants to grow. We use a quantitative growth model of the life cycle of plants, along with U.S. data, to infer the overall size of these payments.

This paper develops the quantitative implications of optimal fiscal policy in a business cycle model. In a stationary equilibrium, the ex ante tax rate on capital income is approximately zero. There is an equivalence class of ex post capital income tax rates and bond policies that support a given allocation. Within this class, the optimal ex post capital tax rates can range from close to independently and identically distributed to close to a random walk. The tax rate on labor income fluctuates very little and inherits the persistence properties of the exogenous shocks; thus there is no presumption that optimal labor tax rates follow a random walk. Most of the welfare gains realized by switching from a tax system like that of the United States to the Ramsey system come from an initial period of high taxation on capital income.

We examine the limiting behavior of cooperative and noncooperative fiscal policies as countries' market power goes to zero. We show that these policies converge if countries raise revenues through lump-sum taxation. However, if there are unremovable domestic distortions, such as distorting taxes, there can be gains to coordination even when a single country's policy cannot affect world prices. These results differ from the received wisdom in the optimal tariff literature. The key distinction is that, contrary to the tariff literature, the spending decisions of governments are explicitly modeled.

We show that optimal monetary and fiscal policies are time consistent for a class of economies often used in applied work, economies appealing because they are consistent with the growth facts. We establish our results in two steps. We first show that for this class of economies, the Friedman rule of setting nominal interest rates to zero is optimal under commitment. We then show that optimal policies are time consistent if the Friedman rule is optimal. For our benchmark economy in which the time consistency problem is most severe, the converse also holds: if optimal policies are time consistent, then the Friedman rule is optimal.

If Exchange Rates are Random Walks, Then Almost Everything We Say About Monetary Policy is Wrong by Fernando Alvarez, Andrew Atkeson and Patrick J. Kehoe. Published in volume 97, issue 2, pages 339-345 of American Economic Review, May 2007

During the Great Recession, US regions that experienced large declines in household debt also experienced large drops in consumption, employment, and wages. We develop a search and matching model in which tighter debt constraints raise the cost of investing in new job vacancies and so reduce job-finding rates and employment. On-the-job human capital accumulation is critical to generating sizable drops in employment: it increases the duration of the benefit flows from posting vacancies, thereby amplifying the employment drop from a credit tightening 10-fold relative to the standard model. Our model reproduces the salient cross-regional features of the US Great Recession.

We analyze the effects of money injections on interest rates and exchange rates when agents must pay a Baumol‐Tobin‐style fixed cost to exchange bonds and money. Asset markets are endogenously segmented because this fixed cost leads agents to trade bonds and money infrequently. When the government injects money through an open market operation, only those agents that are currently trading absorb these injections. Through their impact on these agents’ consumption, these money injections affect real interest rates and real exchange rates. The model generates the observed negative relation between expected inflation and real interest rates as well as persistent liquidity effects in interest rates and volatile and persistent exchange rates.

This paper presents a simple general equilibrium model of optimal taxation in which both private agents and the government can default on their debt. As a benchmark we consider Ramsey equilibria in which the government can precommit to its policies at the beginning of time, but in which private agents can default. We then consider sustainable equilibria in which both government and private agent decision rules are required to be sequentially rational. We completely characterize the set of sustainable equilibria. In particular, we show that when there is sufficiently little discounting and government consumption fluctuates enough, the Ramsey allocations and policies (in which the government never defaults) can be supported by a sustainable equilibrium.

We propose a simple method to help researchers develop quantitative models of economic fluctuations. The method rests on the insight that many models are equivalent to a prototype growth model with time-varying wedges that resemble productivity, labor and investment taxes, and government consumption. Wedges that correspond to these variables—efficiency, labor, investment, and government consumption wedges—are measured and then fed back into the model so as to assess the fraction of various fluctuations they account for. Applying this method to U.S. data for the Great Depression and the 1982 recession reveals that the efficiency and labor wedges together account for essentially all of the fluctuations; the investment wedge plays a decidedly tertiary role, and the government consumption wedge plays none. Analyses of the entire postwar period and alternative model specifications support these results. Models with frictions manifested primarily as investment wedges are thus not promising for the study of U.S. business cycles.