U.S. 30-year fixed-rate mortgage rates fell in the week ending Dec. 15 to 3.94 percent, matching an all-time historic low, according to Freddie Mac.

The 30-year fixed-rate mortgage rate was down from 3.99 percent in the previous week and 4.83 percent in the same time last year. The rate was previously at the all-time low of 3.94 percent on Oct. 6.

The 15-year fixed-rate mortgage was 3.21 percent, a new record low, down from 3.27 percent in the last week and 4.17 percent in the previous year.

Five-year adjustable-rate mortgages (ARMs) had an average rate of 2.86 percent, down from 2.93 percent in the previous week and 3.77 percent in the previous year. One-year ARMs were 2.81 prcent, down from 2.80 percent in the previous week.

Mortgage rates were at or near all-time record lows this week amid a rough environment for housing, said Frank Nothaft, vice president and chief economist of Freddie Mac, in a statement.

Despite the low mortgage rates, housing demand remains weak. New home sales in October were below forecasts, and prices continue to fall.