Rating agencies defend their style of analysis - and hedge their bets

THE two credit-rating agencies that dominate the business come in for flak from all sides. Investors caught holding Enron's investment-grade bonds as their price sank to below that of junk say that Moody's and Standard & Poor's (S&P) are just too slow to spot companies' declining financial health. Equally, say others, they are just too fast when they produce unjustifiably large changes in ratings. Stung by a precipitous downgrade, Tyco, once a high-flying American conglomerate, has had to seek an emergency and very costly refinancing, punishing investors.

The agencies use legions of highly trained analysts with access to top management. Their meticulous reports giving ratings for corporate bonds are designed to give an accurate picture of the bonds' riskiness and, ultimately, the probability of default. Lately, rating agencies have struggled to keep up; it seems a bond's rating tells you ever less about the price that investors are willing to pay. In 1997 two-thirds of debt rated triple-B by S&P was priced within 20 basis points (hundredths of a percentage point) of the average bond with the same rating. Since then, the range has widened. Last year credit spreads' standard deviation, a measure of dispersion, had risen more than sixfold.

The US company Tyco was adversely affected by