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

Interest rates on 30-year fixed-rate mortgages, the most widely used loan, averaged 4.42 percent this week, down from last week's 4.44 percent and its year-ago level of 5.12 percent, according to the survey.

Thirty-year mortgage rates have fallen to record lows for nine straight weeks. Freddie Mac started the survey in April 1971.

Meanwhile, 15-year fixed-rate mortgages averaged 3.9 percent, down from 3.92 percent last week, the lowest level since Freddie Mac began surveying this loan type in 1991. Fifteen-year mortgage rates have hit record lows for six straight weeks.

Freddie Mac said rates on 5/1 adjustable-rate mortgages, set at a fixed rate for five years and adjustable in each following year, was 3.56 percent, unchanged from last week, remaining at its lowest level since Freddie Mac began tracking this loan type in 2005.

One-year ARMs were 3.53 percent, unchanged from last week.

A year ago, 15-year mortgages averaged 4.56 percent; the one-year ARM was 4.69 percent, and the 5/1 ARM was 4.57 percent.

Rock-bottom rates should continue to spur demand for home loan refinancing, putting extra cash into consumers' hands that they can save, use to pay off existing debt or funnel into the economy through extra spending.

Mortgage applications jumped 13 percent in the week ended Aug. 13, fueled more by homeowners refinancing than by new buyers looking for loans, according to an index from the Mortgage Bankers Association. Record low interest rates have yet to spur home sales, which are being weighed down by unemployment and the end of a federally sponsored home-buyer tax credit.

"The weak sales are reflective of the general economic weakness," said Scott Brown, chief economist at Raymond James & Associates in St. Petersburg, Fla. "A lot of it still gets back to the job market. Unless you have a full recovery in the job market, you won't have a full recovery in housing."

Applications for unemployment benefits unexpectedly increased last week to the highest level since November. Initial jobless claims rose by 12,000 to 500,000 in the week ended Aug. 14, Labor Department figures showed Thursday.

The number of contracts to buy existing homes dropped 2.6 percent in June after plummeting 30 percent in May, according to the National Association of Realtors.