ABSTRACT By means of the high ratings that they awarded to subprime mortgage‐backed bonds, the three major rating agencies—Moody's, Standard & Poor's, and Fitch—played a central role in the current financial crisis. Without these ratings, it is doubtful that subprime mortgages would have been issued in such huge amounts, since a major reason for the subprime lending boom was investor demand for high‐rated bonds—much of it generated by regulations that made such bonds mandatory for large institutional investors. And it is (...) even less likely that such bonds would have become concentrated on the balance sheets of the banks, for which they were rewarded by capital regulations that tilted toward high‐rated securities. Why, then, were the agencies excessively optimistic in their ratings of subprime mortgage‐backed securities? A combination of their fee structure, the complexity of the bonds that they were rating, insufficient historical data, some carelessness, and market pressures proved to be a potent brew. This combination was enabled, however, by seven decades of financial regulation that, beginning in the 1930s, had conferred the force of law upon these agencies' judgments about the creditworthiness of bonds and that, since 1975, had protected the three agencies from competition. (shrink)