A historic drop in interest rates is helping U.S. households save more than $3,000 a year on average, allowing consumers to spend more even as their earnings fall, according to a USA Today analysis.

Mortgage interest payments are down 30 percent from their 2007 peak, helping to reshape household budgets and consumer spending.

The economic gain for borrowers overshadows the importance of other stimulus efforts or even higher gasoline prices. A cut in the Social Security payroll tax, in contrast, will save households an average of about $70 a month this year.

“Even if people aren’t paying attention to their interest payments falling, the money builds up in their checking account, and that especially benefits big-ticket items like cars,” said Paul Taylor, chief economist for the National Automobile Dealers Association. Lower rates are letting people spend more on cars for the same monthly payment, boosting the fortunes of automakers.

Americans spent 5.8 percent of their after-tax income paying interest on mortgages, credit cards, car loans and other debt, according to the latest data from the Bureau of Economic Analysis. That’s the smallest share since 1977 and a steep drop from a record high of 9.1 percent in 2007.

Household interest payments fell to an average of $469 per month at the end of last year, down from a peak of $728 in 2007, after adjusting for inflation. That equals $3,100 a year.