Research

Abstract: I study the effect of market incompleteness on the aggregate economy in a model where agents face idiosyncratic, uninsurable human capital investment risk. The environment is a general equilibrium life-cycle model with a version of a Ben-Porath (1967) human capital accumulation technology, modified to incorporate risk. A CARA-normal specification keeps household decisions independent of individual shock realizations. I study stationary equilibria of calibrated cases in which idiosyncratic uninsurable risk arises from specialization risk and career risk. Specialization risk is such that both mean and variance of the return from training are increasing in the endogenous decision to invest in human capital. In the case of career risk, however, only the mean return is increasing in the decision to invest in human capital. With career risk only, stationary equilibria resemble those studied by Aiyagari (1994), and one concludes that the impact of uninsurable idiosyncratic risk is relatively small. With a significant amount of specialization risk however, stationary equilibria are severely distorted relative to a complete markets benchmark. One aspect of this distortion is that human capital is only about 57 percent as large as its complete markets counterpart. This suggests that the two types of risk have very different and quantitatively significant general equilibrium implications.

Abstract: We study a stylized theory of the volatility reduction in the U.S. after 1984---the Great Moderation---which attributes part of the stabilization to less volatile shocks and another part to more difficult inference on the part of Bayesian households attempting to learn the latent state of the economy. We use a standard equilibrium business cycle model with technology following an unobserved regime-switching process. After 1984, according to Kim and Nelson (1999), the variance of U.S. macroeconomic aggregates declined because boom and recession regimes moved closer together, keeping conditional variance unchanged. In our model this makes the signal extraction problem more difficult for Bayesian households, and in response they moderate their behavior, reinforcing the effect of the less volatile stochastic technology and contributing an extra measure of moderation to the economy. We construct example economies in which this learning effect accounts for about 30 percent of a volatility reduction.

Abstract: We study the interaction of multiple large economies in dynamic stochastic general equilibrium. Each economy has a monetary policymaker that attempts to control the economy through the use of a linear nominal interest rate feedback rule. We show how the determinacy of worldwide equilibrium depends on the joint behavior of policymakers worldwide. We also show how indeterminacy exposes all economies to endogenous volatility, even ones where monetary policy may be judged appropriate from a closed economy perspective. We construct and discuss two quantitative cases. In the 1970s, worldwide equilibrium was characterized by a two-dimensional indeterminacy, despite U.S. adherence to a version of the Taylor principle. In the last 15 years, worldwide equilibrium was still characterized by a one-dimensional indeterminacy, leaving all economies exposed to endogenous volatility. Our analysis provides a rationale for a type of international policy coordination, and the gains to coordination in the sense of avoiding indeterminacy may be large.