Financial crises typically occur because firms and financial institutions are highly exposed to aggregate shocks. We propose a theory to explain these exposures. We study a model where entrepreneurs can issue state-contingent claims to consumers. Even though entrepreneurs can use these instruments to hedge negative shocks, they do not necessarily do so because insuring against these shocks is expensive, as consumers are also harmed by them. This effect is self-reinforcing because riskier balance sheets for entrepreneurs imply higher income volatility for the consumers, making insurance more costly in equilibrium. We show that this feedback is quantitatively important and leads to inefficiently high risk exposure for entrepreneurs.

This article studies the macroeconomic implications of imperfect risk sharing implied by a class of New Keynesian models with heterogeneous agents. The models in this class can be equivalently represented as a representative-agent economy with wedges. These wedges are functions of households’ consumption shares and relative wages, and they identify the key cross-sectional moments that govern the impact of households’ heterogeneity on aggregate variables. We measure the wedges using U.S. household-level data and combine them with a representative-agent economy to perform counterfactuals. We find that deviations from perfect risk sharing implied by this class of models account for only 7% of output volatility on average but can have sizable output effects when nominal interest rates reach their lower bound.