Credit ratings perform a function of critical importance to the financial system. We find that
the entry of a third major rating agency coincides with lower overall quality, as measured by both
the levels and informational content of incumbents’ ratings. The negative link between competition
and quality is econometrically robust and unlikely to be explained by the sources of reverse
causality and omitted variables bias we examine. It also appears unlikely that ratings shopping or
growth in overall market share can explain these patterns.
The effect of competition on incumbent quality is of substantial economic magnitude. A one
standard deviation increase in Fitch’s market share is predicted to increase the average firm and
bond rating by between a tenth and half of a step (and increases it significantly more for more
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highly-levered firms). Moving from the 25th to the 75th percentile of our competition measure
reduces the conditional correlation between ratings and bond yields by about a third and reduces the
conditional predictive power for default events at a three year horizon by two thirds.
Calls for more competition in the ratings industry, such as by the U.S. Department of Justice
(1998, 2009), may deserve a caveat. For regulators and policymakers, it is worth considering that
increasing competition in the ratings industry involves the risk of impairing the reputational
mechanism that seemingly underlies the provision of good quality ratings. There may obviously be
benefits of competition in other areas, including reducing the level of rents in rating agencies and
the additional information provided to financial markets by the additional ratings.