Can a Representative Agent Model Represent a Heterogeneous Agent Economy?

Accounting for observed uctuations in aggregate employment, consumption, and real wage using optimality conditions of a representative household often requires preferences that are incompatible with economic priors (e.g., Mankiw, Rotemberg, and Summers, 1985). This discrepancy between the equilibrium model and the aggregate data is often viewed as evidence of the failure of labor-market clearing. We argue that such a conclusion is premature. We construct a model economy where all prices are exible and all markets clear at all times but household decisions are not readily aggregated because of incomplete capital markets and the indivisible nature of labor supply. We demonstrate that if we were to explain the model-generated aggregate time series using decisions of a "fictitious" stand-in household, such a household is likely to have a non-concave or unstable utility. Our analysis suggests that the representative agent model often fails to represent an equilibrium outcome of a heterogeneous agent economy.