The average rate on a 30-year fixed mortgage has fallen to its lowest level on records dating to 1971.

Freddie Mac says the rate for the most popular mortgage has dipped to 4.15 percent from 4.32 percent a week ago. Its previous low of 4.17 percent was reached in November.

The average on the 15-year fixed mortgage has dipped to 3.36 percent, also a record. It's the third straight week of record-low rates for the popular refinancing option.

Mortgage rates typically track the yield on the 10-year Treasury note. Economic fears have drawn investors to the safety of Treasurys, driving down the yield on the 10-year note to barely above 2 percent.

Still, low rates have yet to boost the depressed housing market. Many potential buyers can't afford to borrow.

Copyright 2013 by The Associated Press. All Rights Reserved.