After a slow start, the private mortgage-insurance industry has finally begun to make inroads in the subprime market, as issuers of securities backed by these loans are increasingly turning to MI to bolster their deals. In a recent analysis of second-quarter trends in the residential MBS market, Standard & Poor’s found that 52 percent of the second-quarter deals it rated included deep MI – loan-level insurance added by the lender to extend beyond normal coverage.