U.S. mortgage rates fell in the past week to the latest in a series of record lows amid concerns about the state of the economy, according to a survey released on Thursday by Freddie Mac.

Rock-bottom rates offer a glimmer of hope for a housing market struggling to gain traction since the recent expiration of popular home-buyer tax credits.

Interest rates on 30-year fixed-rate mortgages, the most widely used loan, averaged 4.49 percent for the week to Aug. 5, down from 4.54 percent a week earlier and 5.22 percent a year ago, according to the survey.

Thirty-year rates have fallen to fresh lows in six out of the last seven weeks. Freddie Mac, the second-largest U.S. mortgage finance company, started the survey in April 1971.

Fifteen-year fixed-rate mortgages averaged 3.95 percent, down from 4.00 percent last week, the lowest since Freddie Mac began surveying this loan type in 1991. Fifteen-year rates have hit fresh lows in five of the last seven weeks.

With rates near their lowest since Freddie Mac started the survey, demand for loans to refinance or purchase homes has picked up, boding well for the market and the economy.

“Yet again, interest rates for fixed-rate mortgages and now the hybrid 5-year ARM (adjustable-rate mortgage) fell to … record lows this week following the second-quarter GDP release,” Frank Nothaft, Freddie Mac vice president and chief economist, said in a statement.

Annual revisions cut cumulative growth in U.S. gross domestic product over the past three years to 0.6 percent from 1.4 percent, reducing inflationary pressures and allowing longer-term rates room to ease, he said.

Mortgage rates are linked to yields on both U.S. Treasuries and mortgage-backed securities.

Home sales have fallen since the expiration of government tax credits. To take advantage of them, buyers had to sign purchase contracts by April 30. Contracts originally had to close by June 30 but that was extended by three months.

Cameron Findlay, chief economist at LendingTree.com in Charlotte, North Carolina, said the housing market is vulnerable, with a flood of foreclosures in the pipeline and high unemployment weighing heavily.

“The world essentially collapsed after the tax credits expired,” he said. “This baby cannot walk on its own without government intervention.”

Findlay said his biggest concern is that the economy is going to stall and believes there is a 30 percent chance of a double-dip recession.

“Low mortgage rates are certainly a positive, but jobs growth is more important and without that, a housing rebound will not emerge,” he said.

The U.S. Labor Department said on Thursday new claims for unemployment benefits rose last week to the highest since early April. On Friday it will release July U.S. payrolls data.

The Mortgage Bankers Association said on Wednesday U.S. mortgage applications to purchase homes rose last week for a third straight week as rates tumbled. See [ID:nNLL3JE6B4].

Freddie Mac said the rate on the 5/1 ARM, set at a fixed rate for five years and adjustable each following year, was 3.63 percent, down from 3.76 percent last week, its lowest level since Freddie Mac began tracking this loan type in 2005.

One-year ARMs were 3.55 percent, down from 3.64 last week. [ID:nWAL5JE6FO]

A year ago, 15-year mortgages averaged 4.63 percent, the one-year ARM was 4.78 percent and the 5/1 ARM 4.73 percent.