WASHINGTON – The average U.S. rate on 30-year fixed mortgages was unchanged for a second week, remaining near historic lows.

The average rate on 15-year mortgages also stayed the same.

Low mortgage rates are helping to strengthen the housing recovery.

Mortgage buyer Freddie Mac said Thursday the rate on 30-year loans stayed at 3.53 percent. That’s near the 3.31 percent reached in November, which was the lowest on record dating to 1971.

The rate on 15-year fixed mortgages stayed at 2.77 percent for a second week. The record low is 2.63 percent.

The rate on one-year adjustable mortgages was the only one to change last week. It averaged 2.61 percent, up from 2.53 percent the previous week.

Cheap mortgages are giving a boost to the slowly improving housing market.

Increased sales have helped to push home prices up, which makes consumers feel wealthier and helps to boost consumer spending. In addition, the increased housing demand is boosting new home construction.

Still, housing has a long way to go to achieve a full recovery. And many people are unable to take advantage of the low rates, either because they can’t qualify under stricter lending rules or they lack the money to meet larger down payment requirements.

To calculate average mortgage rates, Freddie Mac surveys lenders across the country on Monday through Wednesday of 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.