Fixed mortgage rates edged up this week, but even 30-year rates below 5 percent have done little to boost home sales. Freddie Mac said Thursday the average rate on the 30-year fixed mortgage rose to 4.81 percent from 4.76 percent the previous week. It hit a 40-year low of 4.17 percent in November.

The average rate on the 15-year fixed mortgage increased to 4.04 percent from 3.97 percent. It reached 3.57 percent in November, the lowest level on records dating back to 1991.

Mortgage rates tend to track the yield on the 10-year Treasury note, which rose this week.

Still, low rates haven’t helped the weak housing market. In February, sales of previously occupied homes fell 9.6 percent and new-home sales tumbled to the slowest pace in nearly a half-century.

High unemployment, a record number of foreclosures and tight lending standards have kept people from making purchases. Other would-be buyers are waiting for home prices to bottom out, which most economists predict won’t happen until midyear.

To calculate average mortgage rates, Freddie Mac collects rates from lenders across the country on Monday through Wednesday of each week. Rates often fluctuate significantly, even within a single day.

The average rate on a five-year adjustable-rate mortgage rose to 3.62 percent from 3.57 percent. The five-year hit 3.25 percent last month, the lowest rate on records dating back to January 2005.

The average rate on one-year adjustable-rate home loans increased to 3.21 percent from 3.17 percent, which was the lowest level in a year for the one-year ARM rate.

The rates do not include add-on fees, known as points. One point is equal to 1 percent of the total loan amount. The average fee for the 30-year fixed loan and 15-year fixed loan in Freddie Mac’s survey was 0.7 point. The average fee for the five-year ARM and the 1-year ARM was 0.6 point.