In spite of mounting losses banks continued to pay dividends during the crisis. We present a model that addresses this behavior. By paying out dividends, a bank transfers value to its shareholders away from creditors, among whom are other banks. This way, one bank's dividend payout policy affects the equity value and risk of default of other banks. When such negative externalities are strong and bank franchise values are not too low, the private equilibrium can feature excess dividends relative to a coordinated policy that maximizes the combined equity value of banks.

We present an economic model of systemic risk in which undercapitalization of the financial sector as a whole is assumed to harm the real economy, leading to a systemic risk externality. Each financial institution's contribution to systemic risk can be measured as its systemic expected shortfall (SES), that is, its propensity to be undercapitalized when the system as a whole is undercapitalized. SES increases in the institution's leverage and its marginal expected shortfall (MES), that is, its losses in the tail of the system's loss distribution. We demonstrate empirically the ability of components of SES to predict emerging systemic risk during the financial crisis of 2007-2009.