Why Did Holdings of Highly Rated Securitization Tranches Differ So Much Across Banks?

We provide estimates of holdings of highly rated securitization tranches of U.S. bank holding companies before the credit crisis and evaluate hypotheses that have been advanced to explain them. Whereas holdings exceeded Tier 1 capital for some large banks, they were economically trivial for the typical bank. Banks with high holdings were not riskier before the crisis using conventional measures, but they performed poorly during the crisis. We find that holdings of highly rated tranches were correlated with a bank's securitization activity. Theories unrelated to the securitization activity, such as “bad incentives” or “bad risk management,” are not supported in the data