Average U.S. mortgage rates are near historically low levels.

Mortgage company Freddie Mac said Thursday that the nationwide average rate for a 30-year loan dipped to 4.12 percent, down from 4.14 last week. The average for the 15-year mortgage, which had taken a big dip the previous week, was unchanged this week at 3.22 percent.

Rates on one-year adjustable mortgages averaged 2.38 percent this week, down from 2.40 percent last week.

Mortgage rates are slightly lower than they were at the same time last year, having fallen recently after climbing last summer when the Federal Reserve began talking about trimming back the monthly bond purchases it has been using to keep long-term rates low.

At 4.12 percent, the rate on 30-year mortgages is down from 4.53 percent at the beginning of this year. Rates have fallen modestly this year as Fed officials have sent strong signals that while they are trimming their monthly bond purchases, they are in no rush to start boosting a key short-term rate the Fed controls.

To calculate average mortgage rate, 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 0.5 point this week, the same as last week. The fee for a 15-year loan, popular in refinancing, was also 0.5 point, unchanged from last week.

The fee on a one-year adjustable rate mortgage was 0.4 point, unchanged from last week.

The average rate on a five-year adjustable rate mortgage was 2.98 percent, unchanged from last week. The fee was 0.4 point, up from 0.3 point last week.