Fixed-rate mortgage rates declined in the week ending Wednesday, with the 30-year mortgage rate at its lowest level at least since tracking began in 1971, mortgage giant Freddie Mac (FRE) said in its weekly survey.

The survey said 30-year fixed-rate mortgages averaged 5.10% with an average 0.7 point, down from 5.14% last week. Last year at this time, the rate was 6.07%.

“The 30-year FRM has not been lower since Freddie Mac started the Primary Mortgage Market Survey in 1971,” Freddie Mac said in its press release.

The 15-year fixed-rate mortgage averaged 4.83% with 0.7 point, down from 4.91% last week. One year ago, it was at 5.68%. This is the lowest level since March 25, 2004.

 “Interest rates for 30-year fixed-rate mortgages fell for the ninth straight week and represented a third consecutive all-time record low since Freddie Mac’s survey began in April 1971,” said Frank Nothaft, Freddie Mac vice president and chief economist, in the press release.

Nothaft noted that the decline was “about 1-1/3 percentage points, or payment savings of approximately $173 a month for a $200,000 loan.” He said that because of the savings, refinancing applications for conventional mortgages jumped sixfold between the weeks ending on Oct. 31 and Dec. 26.

Meanwhile, five-year Treasury-indexed adjustable-rate mortgage rates averaged 5.57% this week with an average 0.7 point, up from 5.49% last week. One year ago, it was averaging 5.78%.

One-year Treasury-indexed ARMs averaged 4.85% this week with an average 0.5 point, downfrom 4.95% last week.  At the same time last year, the 1-year ARM averaged 5.47%.

The lower rates have combined with declining home prices to make housing more affordable, a point Freddie made in its release.

But the lower rates make for one of the few silver linings in the housing-market cloud right now. The recession and credit crunch have prevented many would-be buyers from taking the plunge into new homes. In addition, foreclosures are still at historic highs as well, as people find they can’t keep pace with the rate increases in some mortgage payment plans.

Most experts think housing won’t turn around until late 2009 at the earliest. Still, lower rates can’t hurt as the sector tries to recover its footing.