Fewer net interest margin securitizations were completed in the subprime market last year – a sign of a possible strategic shift among issuers looking for new ways to efficiently manage their residuals. According to data compiled by affiliated newsletter Inside MBS & ABS, $12.71 billion in new NIMs, or bonds backed by such leftover cashflows as prepayment penalties, were issued last year. That marked a steep 21.9 percent drop from 2005. …