We address the following questions concerning bank capital: why are banks so highly levered, what are the consequences of this leverage for the economy as a whole, and how can robust capital regulation be designed to restrict bank leverage to levels that do not generate excessive systemic risk?...

We consider a model in which banks face two moral hazard problems: 1) asset substitution by shareholders, which can occur when banks make socially-inefficient, risky loans; and 2) managerial under-provision of effort in loan monitoring. The privately-optimal level of bank leverage is neither too...