The average rate on a 30-year mortgage was 4.32% this week, compared with 4.39% last week, Freddie Mac said Thursday.

The mortgage buyer noted that during the same period last year the average rate was 4.44%. Freddie Mac also said the average rate on a 15-year fixed mortgage was 3.50%, compared with 3.54% last week and 3.92% last year at this time.

Freddie Mac Chief Economist Frank Nothaft said the Fed's decision to keep interest rates unchanged drove the mortgage rates down. 

He also predicted that the lower rates would “help to maintain the high degree of home-buyer affordability in the market.”

On Wednesday, the National Association of Realtors reported that median existing-home prices declined in the second quarter and 27% of metropolitan areas experiencing price gains from a year ago.

According to the trade association, the median existing single-family home price was $171,900 in the second quarter, compared with $176,800 in the second quarter of 2010.