A sluggish $57.18 billion of new structured mortgage securities backed by agency pass-through collateral were issued during the first quarter of 2006, down 19.6 percent from the previous period. New agency-backed REMIC volume for the first three months of the year was also down 21.3 percent from the same period in 2005, a new Inside MBS & ABS analysis shows. Freddie Mac remained the largest issuer in the market, although its $28.94 billion in first-quarter… [One data table included]