We present a theory of excess stock market volatility, in which market movements are due to trades by very large institutional investors in relatively illiquid markets. Such trades generate significant spikes in returns and volume, even in the absence of important news about fundamentals. We...

This paper proposes that idiosyncratic firm-level fluctuations can explain an important part of aggregate shocks, and provide a microfoundation for aggregate productivity shocks. Existing research has focused on using aggregate shocks to explain business cycles, arguing that individual firm...

A power law is the form taken by a large number of surprising empirical regularities in economics and finance. This article surveys well-documented empirical power laws concerning income and wealth, the size of cities and firms, stock market returns, trading volume, international trade, and...

This paper incorporates a time-varying intensity of disasters in the Rietz-Barro hypothesis that risk premia result from the possibility of rare, large disasters. During a disaster, an asset's fundamental value falls by a time-varying amount. This in turn generates time-varying risk premia and...

This methodological paper presents a class of stochastic processes with appealing properties for theoretical or empirical work in finance and macroeconomics, the "linearity-generating" class. Its key property is that it yields simple exact closed-form expressions for stocks and bonds, with an...

Inattention is a central, unifying theme for much of behavioral economics. It permeates such disparate fields as microeconomics, macroeconomics, finance, public economics, and industrial organization. It enables us to think in a rather consistent way about behavioral biases, speculate about...

A number of consequences emerge. (i) Fiscal stimulus or \helicopter drops of money" are powerful and, indeed, pull the economy out of the zero lower bound. More generally, the model allows for the joint analysis of optimal monetary and fiscal policy. (ii) The Taylor principle is strongly...

This paper proposes a tractable way to model boundedly rational dynamic programming. The agent uses an endogenously simplified, or "sparse," model of the world and the consequences of his actions and acts according to a behavioral Bellman equation. The framework yields a behavioral version of...

A key open question in economics is the practical, portable modeling of bounded rationality. In this short note, I report ongoing progress that is more fully developed elsewhere. I present some results from a new model in which the decision-maker builds a simplified representation of the world....

This paper defines and analyzes a "sparse max" operator, which is a less than fully attentive and rational version of the traditional max operator. The agent builds (as economists do) a simplified model of the world which is sparse, considering only the variables of first-order importance. His...