The last time the rate was lower was the first quarter of 2008, when it was 3.39 percent, according to TransUnion. The firm's records go back to the second quarter of 2007.
The mortgage delinquency rate has been steadily declining over the past two years. At the same time, U.S. home sales and prices have been rebounding while foreclosures have been declining.
Homeowners have seen their finances boosted by rising home values, an improving job market and efforts to restructure home loans so they're more affordable. That has enabled them to make timely payments.
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In addition, many of the risky home loans made before 2008 that went unpaid are no longer a factor, because the homes have been sold or foreclosed upon. Loans issued since then, after banks tightened lending standards, are less likely to go unpaid.
That has helped drive lower late-payment rates among younger borrowers.
The mortgage delinquency rate for borrowers under 30 was 2.34 percent in the second quarter, the lowest of any age group. They also accounted for the smallest slice of borrowers with a home loan at 4.2 percent, according to TransUnion.
By age group, borrowers ages 40-49 had the highest late-payment rate at 4.43 percent. They made up about a quarter of all borrowers with a mortgage.