The 30-year fixed-rate mortgage averaged 6.10%, tumbling 10 basis points from last week to the lowest level since the week ending Oct. 15, 2005, according to Freddie Mac’s latest Primary Mortgage Market Survey. At this time last year, the average was 6.14%.

At 5.73%, the 15-year also fell 10 BPS from a week ago, Freddie reported.

The 10-year Treasury note yield, a guide for long-term mortgage rates, was 3.91% this afternoon, 9 BPS lower than a week earlier and down 12 BPS for the day.

“Interest rates for U.S. Treasury securities have been drifting lower this month over market concerns that the housing slump and stress in the credit markets could slow future economic growth,” Freddie Chief Economist Frank Nothaft said in an announcement. “As a result, interest rates for fixed-rate mortgages had room to slip lower this week.”

With additional data of falling home prices and a continued glut of available homes, “the overall picture does, indeed, appear glum with no immediate relief in sight,” he added.

According to 42 of the 100 mortgage industry individuals surveyed by Bankrate.com this week, rates will fall through mid-January. A third of the panel forecast a rise and a quarter foresaw rates remaining relatively unchanged.

But the Mortgage Bankers Association sees the 30-year averaging 6.2% this quarter and rising 10 BPS in each of the next three quarters to end 2008 at 6.8%.

The 5-year Treasury-indexed hybrid adjustable-rate mortgage averaged 5.86%, slipping 2 BPS from last week, Freddie said.

The 1-year Treasury-indexed ARM average reportedly ticked up 1 BPS to 5.43% this week, while Federal Reserve data showed the 1-year Treasury bill yield itself fell 6 BPS in a week’s period to 3.26% on Tuesday.

The 6-month London Interbank Offered Rate averaged 4.86% for the week ending yesterday, Bankrate.com reported.

The ARM share decreased from the previous week to comprise less than 15% of total mortgage application activity, according to the Mortgage Bankers Association’s application survey for the week ending Nov. 23.

Total mortgage application volume continued descending, by 4 percent from the previous week on a seasonally- and Thanksgiving holiday-adjusted basis, MBA reported. As refinance requests tumbled 15 percent, seasonally-adjusted purchase money demand went up 6%.

The refinance share of total applications sunk to 46% from over half the previous week, MBA said.