We develop a set of necessary and sufficient conditions for equilibria to be determinate in a class of forward-looking Markov-switching rational expectations models and we develop an algorithm to check these conditions in practice. We use three examples, based on the new-Keynesian model of...

This paper provides a mathematical foundation for independent random matching of a large population, as widely used in the economics literature. We consider both static and dynamic systems with random mutation, partial matching arising from search, and type changes induced by matching. Under...

We develop a projection method that can solve dynamic economic models with a large number of state variables. A distinctive feature of our method is that it operates on the ergodic set realized in equilibrium: we simulate a model, distinguish clusters on simulated series and use the clusters'...

A model is developed where firms in a financial system have to settle their debts to each other by using a liquid asset. The question that is studied is how many firms must obtain how much of this asset from outside the financial system to make sure that all debts within the system are settled....

The Schelling model of a "tipping point" in racial segregation, in which whites flee a neighborhood once a threshold of nonwhites is reached, is a canonical model of strategic interdependence. The idea of "tipping" explaining segregation is widely accepted in the academic literature and popular...

We demonstrate that personal connections amongst politicians have a significant impact on the voting behavior of U.S. politicians. Networks based on alumni connections between politicians, as well as common seat locations on the chamber floor, are consistent predictors of voting behavior. For...

I build a simple dynamic model of the formation of an international social network of importers and exporters. Firms can only export into markets in which they have a contact. They acquire new contacts both at random, and via their network of existing contacts. This model explains (i) the...

Governments fighting terrorists have many tactical options, yet these options often yield unintended and counterproductive consequences. This paper models a terrorist organization, a religious group from which the terrorists recruit suicide bombers, and the society in which the terrorists are...

We develop a model of information exchange through communication and investigate its implications for information aggregation in large societies. An underlying state determines payoffs from different actions. Agents decide which others to form a costly communication link with incurring the...