Information Aggregation in a Dynamic Stochastic General Equilibrium Model
We introduce the information microstructure of a canonical noisy rational expectations model (Hellwig 1980) into the framework of a conventional real businesscycle model. Each household receives a private signal about future productivity. In equilibrium, the stock price serves to aggregate and transmit this information. We find that dispersed information about future productivity affects the quantitative properties of our real businesscycle model in three dimensions. First, households' ability to learn about the future affects their consumptionsavings decision. The equity premium falls and the riskfree interest rate rises when the stock price perfectly reveals innovations to future productivity. Second, when noise trader demand shocks limit the stock market's capacity to aggregate information, households hold heterogeneous expectations in equilibrium. However, for a reasonable size of noise trader demand shocks the model cannot generate the kind of disagreement observed in the data. Third, even moderate heterogeneity in the equilibrium expectations held by households has a sizable effect on the level of all economic aggregates and on the correlations and standard deviations produced by the model. For example, the correlation between consumption and investment growth is 0.29 when households have no information about the future, but 0.41 when information is dispersed.
NBER Macroeconomics Annual