NEW YORK (CNNMoney.com) -- Mortgage rates fell for the ninth time in 10 weeks, according to a survey released Thursday.

The 30-year fixed-rate mortgage (FRM) averaged 6.31 percent for the week ending Sept. 28, down from 6.40 percent, according to Freddie Mac's (Charts) Primary Mortgage Market Survey. A year ago, the 30-year FRM averaged 5.91 percent.

The 15-year FRM averaged 5.98 percent this week, down from 6.06 percent last week. A year ago, it averaged 5.48 percent.

Five-year adjustable-rate mortgages (ARMs) came in at 6.00 percent this week, down from 6.08 percent last week. A year ago, they averaged 5.44 percent.

One-year ARMs averaged 5.47 percent, down from 5.54 percent last week. A year ago, the one-year ARM averaged 4.68 percent.

"This week's economic releases, which showed a slight one-year decline in both new and existing house prices in August, fell short of market expectations and prompted market analysts to reassess how much the housing sector will contribute to economic growth in the coming year," said Frank Nothaft, Freddie Mac vice president and chief economist, in a statement.

"As a result, mortgage rates declined even further this week to match those set six months ago. One bright note in the releases was that the average time new homes stood for sale narrowed from 6.6 months to 6.3 months in August, which should mitigate some of the softening of new home prices over the next few months.

"In addition, both lower mortgage rates and a moderation in house price growth should lead to increased housing affordability - especially as family incomes are forecasted to continue rising."

Freddie Mac competes on the secondary market with Citigroup (Charts), Countrywide Financial (Charts) and Fannie Mae (Charts).

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