We analyze the relationship between bank size and risk-taking under the Basel II Capital Accord. Using a model with imperfect competition and moral hazard, we show that the introduction of an internal ratings based (IRB) approach improves upon flat capital requirements if the approach is applied uniformly across banks and if the costs of implementation are not too high. However, the banks’ right to choose between the standardized and the IRB approaches under Basel II gives larger banks a competitive advantage and, due to fiercer competition, pushes smaller banks to take higher risks. This may even lead to higher aggregate risk-taking.

[This article empirically investigates the competitive effects of government bail-out policies. We construct a measure of bail-out perceptions by using rating information. From there, we construct the market shares of insured competitor banks for any given bank, and analyze the impact of this variable on banks' risk-taking behavior, using a large sample of banks from OECD countries. Our results suggest that government guarantees strongly increase the risk-taking of competitor banks. In contrast, there is no evidence that public guarantees increase the protected banks' risk-taking, except for banks that have outright public ownership. These results have important implications for the effects of the recent wave of bank bail-outs on banks' risk-taking behavior.]