Endogenous Risk-Exposure and Systemic Instability

Most research on financial systemic stability assumes an economy in which banks are subject to exogenous shocks, but in practice, banks choose their exposure to risk. This paper studies the determinants of this endogenous risk exposure when banks are connected in a financial network. I show that there exists a network risk-taking externality: connected banks’ choices of risk exposure are strategically complementary. Banks in financial networks, particularly densely connected ones, endogenously expose to greater risks. Furthermore, they choose correlated risks, aggravating the systemic fragility. Banks, however, do have incentives to form networks to protect their charter values. The theory yields several novel perspectives on policy debates.