NEW YORK (MarketWatch) -- U.S. fixed-rate mortgages fell for the third straight week, according to Freddie Mac's survey released Thursday. The national average interest rate on the benchmark 30-year, fixed-rate loan averaged 6.04% in the week ending Thursday, down from last week's 6.14% and the year-ago 6.20%. The 15-year fixed-rate loan averaged 5.73%, down from the week-ago 5.81% and the year-ago 5.83%. The five-year Treasury-indexed hybrid adjustable-rate mortgage averaged 5.87%, compared with 5.98% a week ago and 5.88% a year ago. One-year Treasury-indexed ARMs averaged 5.29% this week, down from last week's 5.33% and the year-ago 5.42%. "Long- and short-term mortgage rates fell for the third consecutive week amid continuing signs of a slowing economy," said Frank Nothaft, Freddie Mac vice president and chief economist.