A shift in the business of rating prime jumbo non-agency MBS nicked a few points off Standard & Poor’s market-leading penetration of the non-agency MBS world, but the company also edged into the lead in rating non-mortgage ABS during the first quarter. According to the Inside Mortgage Finance MBS Database, S&P still was the most active rater of non-agency MBS, having graded some 91.6 percent of first quarter business on a dollar basis. That was… {Two data tables included]