Freddie Mac released the results of its weekly mortgage rate survey Thursday, showing average fixed mortgage rates largely unchanged and near their record lows, helping to keep housing affordability high for those borrowers who are in the market.

The 30-year fixed rate dipped to 3.99 percent (0.7 point) for the week ending December 8, down from last week when it averaged 4.00 percent. Last year at this time, the 30-year rate was 4.61 percent.

At 3.27 percent (0.8 point), the 15-year fixed rate this week averaged just slightly above its all-time low of 3.26 percent on October 6, 2011. The 15-year rate slipped from 3.30 percent last week. A year ago at this time, it was averaging 3.96 percent.

Adjustable-rate mortgages (ARMs) rose slightly this week, but both products included in Freddie’s study are coming off of all-time historic lows recorded last week.

The 5-year ARM is now averaging 2.93 percent (0.5 point), up from 2.90 percent last week. This time last year, the 5-year ARM was at 3.60 percent.

One-year ARMs averaged 2.80 percent (0.6 point) this week. The average was 2.78 percent last week and 3.27 percent at the same time last year.