The regulation of bank capital as a means of smoothing the credit cycle is a central element of forthcoming macro‐prudential regimes internationally. For such regulation to be effective in controlling the aggregate supply of credit it must be the case that: (i) changes in capital requirements affect loan supply by regulated banks, and (ii) unregulated substitute sources of credit are unable to offset changes in credit supply by affected banks. This paper examines micro evidence—lacking to date—on both questions, using a unique data set. In the UK, regulators have imposed time‐varying, bank‐specific minimum capital requirements since Basel I. It is found that regulated banks (UK‐owned banks and resident foreign subsidiaries) reduce lending in response to tighter capital requirements. But unregulated banks (resident foreign branches) increase lending in response to tighter capital requirements on a relevant reference group of regulated banks. This “leakage” is substantial, amounting to about one‐third of the initial impulse from the regulatory change.

We assemble bank-level and other data for Fed member banks to model determinants of bank failure. Fundamentals explain bank failure risk well. The first two Friedman-Schwartz crises are not associated with positive unexplained residual failure risk, or increased importance of bank illiquidity for forecasting failure. The third Friedman-Schwartz crisis is more ambiguous, but increased residual failure risk is small in the aggregate. The final crisis (early 1933) saw a large unexplained increase in bank failure risk. Local contagion and illiquidity may have played a role in pre-1933 bank failures, even though those effects were not large in their aggregate impact.

The authors thank George Pennachi for helpful comments, Ven Vitale for research assistance, and the National Science Foundation (SBR-9409768) for financial support. This paper is part of NBER's research program in Development of the American Economy. Any opinions expressed are those of the authors and not those of the National Bureau of Economic Research.

The consequences of bank distress for the economy during the Depression remain an area of unresolved controversy. Since John M. Keynes (1931) and Irving Fisher (1933), mac-* Calomiris: Graduate School of Business,