WASHINGTON (AP) — Long-term U.S. mortgage rates fell this week for the second week in a row, despite the Federal Reserve's efforts to lift borrowing costs.

Mortgage buyer Freddie Mac says the rate on 30-year, fixed-rate mortgages slid to 3.92 percent from 3.96 percent the previous week. While historically low, that is still above last year's average of 3.65 percent.

The rate on 15-year, fixed-rate home loans, popular with homeowners who are refinancing their mortgages, eased to 3.2 percent from 3.23 percent last week.

Mortgage rates haven't increased much even though the Federal Reserve has boosted its benchmark rate four times in the past 18 months. That's because mortgage rates follow the yield on the 10-year Treasury note, which is influenced by many factors. Greater demand by overseas investors can lower the yield.

To calculate average mortgage rates, Freddie Mac surveys lenders across the country between Monday and Wednesday each week. The average doesn't include extra fees, known as points, which most borrowers must pay to get the lowest rates. One point equals 1 percent of the loan amount.

The average fee for a 30-year mortgage slipped to 0.5 point from 0.6 point last week. The fee on 15-year loans was unchanged at 0.5 point.

Rates on adjustable five-year loans dipped to 3.18 percent from 3.21 percent last week. The fee held steady at 0.5 point.