Risk management, although of major importance in the banking industry in practice, plays only a minor role in the theory of banking. We reduce this gap by putting forward a model in which risk managers – specialists that can find out correlations between risky assets – endogenously take over typical functions of banks. They grant loans, they consult on financial questions with firms that are threatened by bankruptcy, and they sign tailor-made hedge transactions with these firms. Delegation costs are innately low if banks assume the function of risk managers in an economy. Risk management can be seen as a core competence of banks.

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.