Strong Economic Fundamentals Boost MBS Credit Ratings in 2003, S&P Says A record number of MBS credit ratings were changed during 2003 as broadly improving market fundamentals boosted the strength of a wide range of transactions, says Standard & Poor’s. Surveillance activity for the year resulted in 1,288 rating changes, consisting of 1,192 upgrades, and 96 downgrades. Upgrades in 2003 outshined 2002’s numbers by 558, thanks to strong collateral performance, the rating agency notes