The average 30-year fixed mortgage has been below 4 percent for every week but one in 2012, Freddie Mac said.
In the current week, interest rates for 30-year, fixed-rate loans dropped from 3.56 percent to 3.53 percent with 0.7 points.
In the same week of 2011, interest rates for 30-year loans averaged 4.52 percent.
For 15-year loans in the week ending Thursday, interest rates fell from 2.86 percent to 2.83 percent with an average 0.6 points. A year ago, 15-year loan rates averaged 3.66 percent.
"With little signs of inflation and the Federal Reserve's 'Operation Twist' keeping U.S. treasury bond yields in check, fixed mortgage rates are remaining low and helping to stir the housing market," said Frank Nothaft, vice president and chief economist at Freddie Mac.
A five-year treasury-indexed hybrid adjustable-rate mortgage in the week ending Thursday averaged 2.69 percent with an average 0.6 points, down from last week when it averaged 2.74 percent.
A one-year treasury-indexed ARM loan averaged 2.69 percent this week with an average 0.4 point, unchanged in the week.