Mortgage insurer MGIC Investment Corp. (MTG) posted a loss of $165.2 million, or 82 cents a share, for the third quarter on falling revenue and lower net premiums. The insurer’s third-quarter loss compares to a loss of $51.5 million, or 26 cents a share, in the third quarter of 2010. Revenue for the most recent third quarter hit $337.2 million, down from $382.3 million last year. Meanwhile, net premiums fell from $279 million in last year’s third quarter to $255.7 million in the most recent quarter. During the third quarter, MGIC wrote $3.9 billion in new insurance, up from $3.5 billion a year ago. Refinancing activity tied to the federal government’s Home Affordable Refinance Program accounted for $645.8 million of the new insurance written by MGIC during the period. Still, the HARP transactions are not included in the company’s new business accounting because they are treated as modifications of existing insurance. The percentage of delinquent loans insured by MGIC fell to 13.49% of the total portfolio in 3Q, down from 15.11% last year. Losses on loans in the third quarter grew to $462.7 million from $384.6 million last year because of an increase in new claims on loans that were previously classified as delinquent and a net increase in new delinquencies. Write to Kerri Panchuk.