WASHINGTON (November 21, 2012)--Average U.S. rates on fixed mortgages fell to record lows again this week, a trend that is boosting home sales and aiding the housing recovery, mortgage buyer Freddie Mac said Wednesday.

Freddie Mac said the average rate on the 30-year loan dipped to 3.31 percent, the lowest on records dating back to 1971 and down from 3.34 percent last week, the previous record low.

The average on the 15-year fixed mortgage also dropped to 2.63 percent, down from 2.65 percent last week and also a new record.

The average rate on the 30-year loan has been below 4 percent all year.

It has fallen further since the Federal Reserve started buying mortgage bonds in September to encourage more borrowing and spending.