MICA said the numbers showed 73,880 insured borrowers were at least 60 days late on payments in April. That is up from 43,161 a year earlier. But the increase includes both newly reported defaults for the month, as well as previously unreported defaults by one of the major lenders, said MICA.
The trade group said it had no way of adjusting the numbers to account for the change in data reporting.
"While the change in reporting methodology by a major lender has resulted in an increase in reported delinquencies, it is important to note that this is a one-time adjustment," MICA's Executive Vice President Suzanne Hutchinson said in a statement.
"Overall, the market is returning to fundamentals," she added, noting there was an 11.7 percent increase in new insurance written in the month, reflecting a "return to quality in the marketplace."
MICA compiles its data from information provided by American International Group Inc.'s, United Guaranty Corp, Genworth Financial Inc., MGIC Investment Corp, Old Republic International Corp, PMI Group Inc., and Triad Guaranty Inc.