The average rate on the 30-year fixed mortgage has dipped to near its record low, keeping home-buying and refinancing affordable.

Mortgage buyer Freddie Mac said Thursday that the rate on the 30-year loan dropped to 3.88 percent this week, down from 3.9 percent. In February, the rate hit 3.87 percent, the lowest since long-term mortgages began in the 1950s.

The 30-year loan is the most common financing option for home buyers.

The average on the 15-year fixed-rate mortgage, popular with homeowners who are refinancing, dipped to 3.12 percent, down from 3.13 percent last week. The national average hit an all-time low of 3.11 percent two weeks ago.

Cheaper mortgages have so far done little to boost home sales. Sales of both previously occupied homes and new homes fell in March. Analysts suspect some of that weakness reflected a warm winter, which pulled sales that would normally occur during the spring buying season into January or February.

In addition, some potential buyers are skeptical about purchasing a home with prices still falling. And many Americans are still struggling with damaged credit.

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

The average rate does not 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.

For the five-year adjustable loan, the average rate rose to 2.85 percent, up from 2.78 percent. The average on one-year adjustable loans dropped to 2.74 percent, down from 2.81 percent.