Bank capital requirements are the focus of contentious and heated debates. Since they limit banks’ ability to take on risk and leverage, owners and managers almost always argue for lowering them. To reduce the likelihood of using public funds for further bailouts, both libertarians and progressives argue strenuously that they should be higher. Focusing on the balance between the social benefits of a more resilient financial system and the social costs of curtailing liquidity and loan provision, academicians usually conclude that current levels are too low. So, with well-financed banks and their lobbyists on one side, and a cohort of advocates armed with academic research on the other, regulators are caught in the middle. To whom should they listen?

The answer to this question is an empirical one, so it is important to base any conclusions on a fair and balanced reading of the evidence. Regular readers of this blog will be unsurprised that we continue to maintain that bank capital requirements should be higher than they were even before the Federal Reserve started began its stealth campaign to relax them several years ago. If we were to pick a number, we would start with a leverage ratio—the ratio of common equity to total assets (including off-balance sheet exposures)—that is in the range of 10 to 15 percent, and possibly higher. The risk-weighted equivalent would be about twice as high in the United States (or three times as high in Europe). (The exact numbers depend on the intricacies of accounting standards.) The one thing we would not be arguing for is a further erosion of capital requirements from their current level.

We start with a short reminder about why we need capital requirements in the first place….