The IMF Working Papers series is designed to make IMF staff research available to a wide audience. Almost 300 Working Papers are released each year, covering a wide range of theoretical and analytical topics, including balance of payments, monetary and fiscal issues, global liquidity, and national and international economic developments.
This paper describes and evaluates the sovereign credit ratings methodologies of Standard & Poor's, Moody's Investors Service, and Fitch Ratings. A simple definition of ratings failure-based on ratings stability-is proposed and tested, pointing to falling failure rates, consistent upside bias, and strong interagency correlation. Possible causes of ratings failure are separated into informational, analytical, revenue bias, and other incentive problems, each of which is discussed. The paper seeks to highlight methodological developments after the Asian crisis, particularly with regard to the estimation of contingent liabilities and the assessment of international reserves adequacy.