By Amy Hoak

Rates on conforming mortgages fell again this week, with the 30-year fixed-rate mortgage hitting a record low of 4.78% for the week ending April 2, according to Freddie Mac's weekly survey results released Thursday.

The 30-year fixed-rate mortgage averaged 4.85% last week, and 5.88% a year ago. This week, it's at its lowest level since the survey began in 1971.

Rates on 15-year fixed-rate mortgages also hit a record low, averaging 4.52% this week. The mortgage averaged 4.58% last week and 5.42% a year ago. It hasn't been lower since Freddie Mac began tracking the mortgage in 1991.

Five-year Treasury-indexed hybrid adjustable-rate mortgages averaged 4.92%, another record low; Freddie Mac has tracked this mortgage since 2005. The ARM averaged 4.96% last week and 5.59% a year ago.

One-year Treasury-indexed ARMs averaged 4.75%, down from 4.85% last week. The ARM averaged 5.19% a year ago. It hasn't been lower since Sept. 29, 2005, when it averaged 4.68%.

To obtain the rates, the fixed-rate mortgages and the five-year ARM required payment of an average 0.7 point. The one-year ARM required an average 0.6 point. A point is 1% of the mortgage amount, charged as prepaid interest.

"Mortgage rates followed other interest rates lower this week amid reports of slower economic growth" said Frank Nothaft, Freddie Mac chief economist, in a news release. "The final estimate of economic growth in the fourth quarter was revised lower and personal incomes fell 0.2% in February, below the market consensus."

"On a positive note, pending existing home sales rose 2.1% in February, marking the second increase in three months as potential homebuyers are taking advantage of historically low mortgage rates and falling home prices," he continued. "Serving as a spur to sales, housing affordability reached an all-time high in February 2009 since the series' inception in 1971, according to the National Association of Realtors. By region, sales surged by nearly a third in the Northeast and Midwest, but fell in the West."

Earlier this week, the Mortgage Bankers Association reported that the volume of mortgage applications filed for the week ended March 27 rose a seasonally adjusted 3%, compared with the week before.

-Amy Hoak; 415-439-6400; AskNewswires@dowjones.com