Freddie Mac says the average interest rate on a 30-year fixed mortgage fell to 4.01% this week from 4.09% a week ago. This week's rate is the lowest since 1951.

The average rate on a 15-year fixed mortgage ticked down to 3.28%. Economists say that's the lowest ever for that loan.

Mortgage rates tend to track the yield on 10-year Treasury notes. Rates could fall further after the Federal Reserve announced last week that it would try to push long-term rates down further.