WASHINGTON (AP) — Long-term U.S. mortgage rates were flat to slightly lower this week, as the key 30-year rate marked a new low for the year.

Mortgage buyer Freddie Mac said Thursday the average rate on 30-year fixed-rate home loans slipped to 3.94 percent from 3.95 percent last week. The rate stood at 3.66 percent a year ago and averaged 3.65 percent in 2016, the lowest level in records dating to 1971.

The rate on 15-year mortgages held steady from last week at 3.19 percent.

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 was unchanged this week at 0.5 point. The fee on 15-year loans also held steady at 0.5 point.

Rates on adjustable five-year loans rose to 3.11 percent from 3.07 percent last week. The fee increased to 0.5 point from 0.4 point.