The rising number of conventional purchase loans with debt-to-income ratios exceeding 45 percent combined with low credit scores has prompted two private mortgage insurers to take drastic action. Mortgage Guaranty Insurance Corp. and National MI have announced they will insure loans with DTIs exceeding 45 percent only when their credit score is 700 or greater. Mark Zimmerman, MGIC’s senior vice president for investor relations, said origination of such loans took off last summer when Fannie Mae eased guidelines on loans with 45 percent and above DTI. Fannie updated Desktop Underwriter by removing offsetting and compensating factors and started accepting the loans automatically instead of by referral. Freddie Mac does not accept such loans. Zimmerman said MGIC’s new guideline applies to loans with an agency automated underwriting system response. The company’s non-agency ...