Bond insurers backed a record number of asset-backed securities last year, thanks in large part to continued demand from subprime originators. But there are indications that mortgage insurance may be chipping away at the guarantors’ market share. According to the Association of Financial Guaranty Insurors, the industry insured a record $171.3 billion of asset-backed securities in 2000, an increase of 21 percent from 1999’s figure. Overall, ABSs accounted for nearly 63 percent of insurance issued