Net interest margin securities accounted for a smaller share of the subprime MBS market during the first nine months of 2004. According to data compiled by affiliated newsletter Inside MBS & ABS, issuance of NIMs – or securities backed by such residual cash flows as prepayment penalties – totaled $11.09 billion through the end of September. That performance – a record – marked an 86.7 percent increase from last year’s nine-month mark.