Dirk Bergemann; Stephen Morris
Abstract: In an economy of interacting agents with both idiosyncratic and aggregate shocks, we examine how the structure of private information influences aggregate volatility. The maximal aggregate volatility is attained in a noise free information structure in which the agents confound idiosyncratic and aggregate shocks, and display excess response to the aggregate shocks, as in Lucas . For any given variance of aggregate shocks, the upper bound on aggregate volatility is linearly increasing in the variance of the idiosyncratic shocks. Our results hold in a setting of symmetric agents with linear best responses and normal uncertainty. We establish our results by providing a characterization of the set of all joint distributions over actions and states that can arise in equilibrium under any information structure. This tractable characterization, extending results in Bergemann and Morris , can be used to address a wide variety of questions linking information with the statistical moments of the economy.
JEL classification: C72, C73, D43, D83
Keywords: Idiosyncratic shocks, Aggregate shocks, Volatility, Confounding information, Moment restrictions, Bayes correlated equilibrium