We reexamine several bodies of data on the growth of output, labor, and capital, within the context of a model that admits the possibility of an externality to the capital input. The model is an augmented version of Paul Romer's (1987) reformulation of the Solow model. Unlike Romer, however, we...

We ask what level of migration would maximize world welfare. We find that skill-neutral policies are never optimal. An egalitarian welfare function induces a policy that entails moving mainly unskilled immigrants into the rich countries, whereas a welfare function skewed highly towards the rich...

We study how innovation and technology diffusion interact to endogenously determine the shape of the productivity distribution and generate aggregate growth. We model firms that choose to innovate, adopt technology, or produce with their existing technology. Costly adoption creates a spread...

Uncertainty in both financial markets and the real economy rises sharply during recessions. We develop a model of informational interdependence between financial markets and the real economy, linking uncertainty to information production and aggregate economic activities. We argue that there...

When monetary policy is subject to regime switches conditions for determinacy become more complex. Davig and Leeper (2007) and Farmer, Waggoner and Zha (2009a) have studied such conditons. Using some new results from stochastic processes, we characterize the moments of the stationary...

We formalize the Keynesian insight that aggregate demand driven by sentiments can generate output fluctuations under rational expectations. When production decisions must be made under imperfect information about demand, optimal decisions based on sentiments can generate stochastic...

We examine global dynamics under infinite-horizon learning in New Keynesian models where the interest-rate rule is subject to the zero lower bound. As in Evans, Guse and Honkapohja (2008), the intended steady state is locally but not globally stable. Unstable deflationary paths emerge after...

Will fast growing emerging economies sustain rapid growth rates until they "catch-up" to the technology frontier? Are there incentives for some developed countries to free-ride off of innovators and optimally "fallback" relative to the frontier? This paper models agents growing as a result of...

We show that self-fulfilling equilibria and indeterminacy can easily arise in a simple financial accelerator model with reasonable parameter calibrations and without increasing returns in production. A key feature for generating indeterminacy in our model is the countercyclical markup due to the...

We study a model where some agents have private information about risky asset returns and trade to obtain capital gains, while others acquire the risky asset and hold it to maturity, forming expectations of returns based on market prices. We show that under such a structure, in addition to fully...