Dynamic Bank Capital Requirements

The Basel III Accord requires countercyclical capital buffers to protect the banking system against potential losses associated with excessive credit growth and buildups of systemic risk. In this paper, I provide a rationale for time-varying capital requirements in a dynamic general equilibrium setting. An optimal policy trades off reduced inefficient lending with reduced liquidity provision. Quantitatively, I find that the optimal Ramsey policy requires a capital ratio that mostly varies between 4% and 6% and depends on economic growth, bank supply of credit, and asset prices. Specifically, a one standard deviation increase in the bank credit-to-GDP ratio (GDP) translates into a 0.1% (0.7%) increase in capital requirements, while each standard deviation increase in the liquidity premium leads to a 0.1% decrease. The welfare gain from implementing this dynamic policy is large when compared to the gain from having an optimal fixed capital requirement.