Overall, events have shown that the credit rating agencies severely understated the risk of mortgage backed bonds and CDOs. Beginning in mid2007, the agencies downgraded tens of billions in debt, with some ratings falling from AAA to B.14 How can bond fall from “best quality” to “highly speculative” overnight? Similar to the Enron example below, the credit rating agencies did not do a very good job of predicting credit risk on a timely basis.