Bank Overleverage and Macroeconomic Fragility

This paper develops a dynamic general equilibrium model that explicitly includes a banking sector with a maturity mismatch. We demonstrate that, despite the perfect competition in the banking sector, rational banks take on excessive risks systemically, resulting in overleverage and inefficiently high crisis probabilities. The model accounts for the banks' rational over-optimism regarding future capital prices which arises from pecuniary externalities on their own solvency. Using the model as an example, we introduce MSR (marginal systemic risk) as a general measure to assess the macroeconomic exposure to systemic risks.