Bank regulation and market structure

In our model, banks, heterogeneous in terms of entry costs, compete a la Salop for depositors on the unit circle. When capital requirements, intended to prevent risk shifting, are increased, the resulting costs are passed on to depositors in the form of reduced deposit rates or quality of service. This may induce depositors to migrate to unregulated shadow banks, the consequence being a change in the market structure for regulated banks: for low levels of capital requirements we observe monopolistic competition, while for higher levels constrained oligopoly and, finally, local monopoly. Under the latter two types of market structure, higher capital requirements reduce the profit margins and franchise values of banks, which may have the unintended effect of inducing banks to increase the riskiness of their investments.