NEW YORK - The average rate on the 30-year fixed mortgage edged up this week as bond yields increased.

Freddie Mac said Thursday the average rate rose to 4.81 percent this week from 4.80 percent the previous week. It hit a 40-year low of 4.17 percent in November.

The average rate on the 15-year loan slipped to 4.08 percent from 4.09 percent. It reached 3.57 percent in November, the lowest level on records starting in 1991.

Rates have been little changed this year after spiking more than half a percentage point in the last two months of 2010. Investors sold off Treasury bonds during that time, driving yields lower. Mortgage rates tend to track the yield on the 10-year Treasury note.

High foreclosures, job worries and expectations that home prices will fall further have kept many potential homebuyers on the sidelines. Historically low mortgage rates haven't been enough to jumpstart the housing market.

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 fell to 3.69 percent from 3.70 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 was unchanged at 3.26 percent.

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 and 15-year loan in Freddie Mac's survey was 0.8 point. The average fee for the five-year ARM was 0.7 point, and the fee for the 1-year ARM was 0.6 point.