Monday, August 8, 2011

S&P's ratings quality

S.&P.’s bond ratings from five years ago would have told you almost nothing about the risk of a default today. They had no insight about the threats in European markets, nor about which countries in Europe were relatively more likely to default. (Norway, which remains among the most solvent countries in the world, had a AAA rating in 2006, but so did Ireland and Spain.)

By comparison, simply looking at a country’s ratio of net debt to G.D.P. would have been a better predictor of default. It wouldn’t have done well by any means: it only explains about 12 percent of default risk. Still, this simple statistical indicator does better than the S.&P. ratings. ...

In fact, the evidence from the past five years suggests that it may be worthwhile to adopt a contrarian investing strategy that specifically bets against S.&P.’s ratings. ...

Investors think, for instance, that France is 2 or 3 times more likely to default in the next five years than the United States based on France’s exposure to Greek debt. However, France maintains its AAA rating whereas the U.S. was just downgraded to AA+.
--Nate Silver, NYT, on S&P's sovereign track record