Two firms, Standard & Poor’s and Moody’s Investors Service, dominated the market for rating subprime MBS in the early part of 2006, a new Inside B&C Lending analysis reveals. As usual, S&P was the top rating agency when it came to subprime business during the first quarter. The firm rated $121.25 billion in subprime MBS deals, or 98.2 percent of the total $123.48 billion in total issuance. That represents a slight increase from 2005,… [One data table included]