Washington Mutual was the most active issuer of prime-grade, non-agency mortgage securities in 2002, heaving a total of $40.8 billion in new issuance into last year’s record market. A total of $228.9 billion of prime non-agency MBS were issued last year, up 46.5 percent from the industry’s output in all of 2001. Prime non-agency MBS include deals backed exclusively by loans over the Fannie/Freddie