U.S. mortgage rates dropped to a record low, the first decline in a month, as the Federal Reserve began a program to buy Treasury bonds to support the economy.

The rate for a 30-year fixed loan fell to 4.17 percent in the week ended today from 4.24 percent, Freddie Mac said in a statement. That was the lowest level in the McLean, Virginia- based mortgage-finance company’s records dating to 1971. The average 15-year rate declined to 3.57 percent from 3.63 percent.

The Fed announced last week that it would buy $600 billion of Treasuries to keep interest rates low and boost economic growth, a method known as quantitative easing. Yields on government bonds serve as a benchmark for other debt, signaling home loan rates may fall further after seven months of declines.

“The quantitative easing is helping to lower interest rates overall, and as a result, the longer-term mortgage interest rates are also falling,” Celia Chen, a housing economist at Moody’s Analytics Inc. in West Chester, Pennsylvania, said in a telephone interview.

The previous record low for the 30-year rate was 4.19 percent, reached in the week ended Oct. 14. The rate tumbled from a high of 5.21 percent in April as concern that an economic recovery may falter increased demand for the safety of Treasuries and government-supported bonds tied to home loans.

Refinancings Jump

The falling mortgage rates have boosted homeowner refinancings. The number of mortgage applications in the U.S. increased 5.8 percent in the week ended Nov. 5, the Mortgage Bankers Association’s index showed yesterday.

Refinancing climbed 6 percent and purchase applications rose 5.5 percent, the most since Oct. 1, the Washington-based group said. The refinancing gauge has more than doubled since January.

Sales of U.S. existing homes rose in September by the most on record, a sign low rates are helping stabilize an industry that’s battling record foreclosures and unemployment near a 26- year high.

Purchases increased 10 percent to a 4.53 million annual rate from 4.12 million in August, the National Association of Realtors said Oct. 25. That beat the 4.3 million pace forecast by economists, according to the median estimate in a Bloomberg survey.

Slow job creation and homebuyer difficulties in getting credit may limit the effects of lower rates on the housing market, Chen said. About 14.2 million U.S. homeowners owe more than their houses are worth, she said.

The median U.S. home price fell 0.2 percent in the third quarter from a year earlier to $177,900, the National Association of Realtors said in a report today. Falling values make it hard for homeowners to trade up, Chen said.

“Even though interest rates are very low and affordability is great, I think the demand for homes and home sales will still be pretty soft this year,” she said.