Aggregate Risk, Bank Competition and Regulation in General Equilibrium

We develop a general equilibrium model of competitive banks to examine the optimal design of bank regulation. There is a continuum of equilibria of the unregulated economy that feature varying relative sizes of the financial and real sectors. The unregulated economy underinvests (overinvests) in production when aggregate risk is below (above) a threshold. An efficient allocation is implemented by a range of regulatory policies comprising of capital and liquidity requirements, deposit insurance, and bailouts financed by taxes, but there is a unique regulated equilibrium for a given regulatory policy. Capital and liquidity requirements move in opposing directions; an optimal regulatory policy that features a stricter capital requirement has a looser liquidity requirement. When aggregate risk is low, the efficient allocation can be implemented via deposit insurance and taxation, but capital and liquidity requirements are necessary to ensure a unique regulated equilibrium. When aggregate risk is high, all four regulatory tools are essential components of an optimal regulatory policy. Capital and liquidity requirements that implement efficient regulatory policies do not vary with aggregate risk when it is below a threshold, but become tighter as aggregate risk increases above the threshold. Depositor subsidies via deposit insurance and tax shields are efficient when aggregate risk is low, but inefficient when it is high.