Wednesday, May 21, 2008

Which Ratings Model is Broken?

by Tanta on 5/21/2008 08:10:00 AM

Via naked capitalism, there is this ugly report in the Financial Times:

Moody’s awarded incorrect triple-A ratings to billions of dollars worth of a type of complex debt product due to a bug in its computer models, a Financial Times investigation has discovered.

Internal Moody’s documents seen by the FT show that some senior staff within the credit agency knew early in 2007 that products rated the previous year had received top-notch triple A ratings and that, after a computer coding error was corrected, their ratings should have been up to four notches lower.
That's bad. That's really bad. But then there are these two paragraphs at the end of the article:
The world’s other major credit agency, Standard and Poor’s, was the first to award triple A status to CPDOs but many investors require ratings from two agencies before they invest so the Moody’s involvement supplied that crucial second rating.

S&P stood by its ratings, saying: “Our model for rating CPDOs was developed independently and, like our other ratings models, was made widely available to the market. We continue to closely monitor the performance of these securities in light of the extreme volatility in CDS prices and may make further adjustments to our assumptions and rating opinions if we think that is appropriate.”
The implication here, that Moody's jiggered its model to arrive at the same ratings S&P had already arrived at--presumably to keep the "second opinion" business--is ugly. However, the implication that Moody's had to fudge the numbers in order to come up with AAA on these deals but S&P came up with AAA with a "correct" model is something I for one am having a hard time with.