Private mortgage insurers represented by the Mortgage Insurance Companies of America wrote $4.9 billion in new business in January, down 23% from $6.4 billion the same month a year ago.

In December, MICA wrote $5.8 billion in new business.

MICA reported its member companies — including Genworth, Mortgage Guaranty Insurance Corp., Radian Guaranty and Republic Mortgage Insurance Co. — had $399 billion in primary insurance in force in January. That is down 47% from nearly $748 billion in January 2011.

Many members of the organization recently posted increased earnings in 2011.

Radian earned $302.2 million in 2011, up from a loss of $1.8 billion a year earlier. The company said the credit quality on insured loans improved in the fourth quarter.

Genworth reported income of $107 million in the fourth quarter, compared to a net loss of $161 million in the same period in 2010, driven in part by mortgage insurance results.

Defaults outpaced loan cures in January with MICA reporting that insurers under its umbrella had 29,348 loan defaults insured by the industry, down 55% from 64,687 the same month a year ago. The organization reported 23,728 cures, down 53% from 50,820 a year ago.

About 21,904 borrowers used private mortgage insurance to buy or refinance a home, holding steady after January's total of 21,896. Member companies received 24,097 applications, inching down from 25,789 applications the same month a year ago.