Banking industry dynamics and size-dependent capital regulation

This paper presents a general equilibrium model with a dynamic banking sector to characterize optimal size-dependent bank capital regulation (CR). Bank leverage choices are subject to the risk-return trade-off: high leverage increases expected return on capital, but also increases return variance and bank failure risk. Financial frictions imply that bank leverage choices are socially inefficient, providing scope for a welfare-enhancing CR that imposes a cap on bank leverage. The optimal CR is tighter relative to the pre-crisis benchmark. Optimal CR is also bank specific, and tighter for large banks than for small banks. This is for three reasons. First, allowing small banks to take more leverage enables them to potentially grow faster, leading to a growth effect. Second, although more leverage by small banks results in a higher exit rate, these exits are by the less efficient banks, leading to a cleansing effect. Third, failures are more costly among large banks, because these are more efficient in equilibrium and intermediate more capital. Therefore, tighter regulation for large banks renders them less prone to failure, leading to a stabilization effect. In terms of industry dynamics, tighter CR results in a smaller bank exit rate and a larger equilibrium mass of better capitalized banks, even though physical capital stock and wages are lower. The calibrated model rationalizes various steady state moments of the US banking industry, and provides general support for the Basel III GSIB framework.