"What's really going on is there're a lot of folks who have been delinquent for a very long time, and we're not really adding a lot of new people to the delinquency numbers," Martin said.
The number of mortgages gone unpaid two months or more climbed 54 percent in 2007 from the previous year, increased 53 percent in 2008 and rose 50 percent in 2009, according to TransUnion.
The decline has been far slower, with mortgage delinquency levels falling 7 percent in 2010 from the year before, 6 percent in 2011 and 14 percent last year, the firm said.
All told the 40 percent of all mortgages taken out by borrowers since 2009 only make up 10 percent of home loans that have gone unpaid.
That's partly due to lenders tightening the criteria needed to qualify for a loan, including larger down payments. And even with mortgage rates hovering near all-time lows, borrowers are typically getting fixed-rate, 30-year mortgages these days.
"That's had the effect that those borrowers are able to make their payments," Martin said.
That's kept the mortgage delinquency rate from creeping higher. Still, the trove of pre-2009 loans that are behind two months or more remain a considerable drag.
Even at a 4-year low, the mortgage delinquency rate is still well above the 1 percent to 2 percent average historical range, an indication that many homeowners still are struggling to make their payments.
Before the housing bust, mortgage delinquencies were running at less than 2 percent nationally.
TransUnion anticipates the national mortgage delinquency rate will continue declining through the end of March, though it expects the rate to remain above 5 percent.
At the state level, Florida led the nation in the fourth quarter with the highest mortgage delinquency rate of any state at 12.47 percent. It was followed by Nevada at 10.45 percent; New Jersey at 7.72 percent; and, Maryland at 6.88 percent.