The number of Americans who filed mortgage applications rose 4.1% last week, as homeowners continued to take advantage of low interest rates when refinancing, a leading trade group said Wednesday. The Mortgage Bankers Association's weekly mortgage applications survey for the week ending Aug. 12 noted its market composite index – a measure of mortgage loan applications – grew 4.1% on a seasonally adjusted basis, while the same index increased 3.6% on an unadjusted basis. As interest rates remained low in the face of rocky economic data, the refinance index continued its upward tilt last week, rising 8%, but remaining 16.3% below year ago levels. Meanwhile, the seasonally adjusted purchase index fell 9.1% as shaky economic data kept potential homebuyers on the sidelines. "Unprecedented volatility in the stock market last week amid additional signs that the economy has slowed led to further drops in mortgage rates, with the 15-year rate reaching a new low for the MBA survey," said Mike Fratantoni, MBA vice president of research and economics. "Purchase application activity fell sharply over the previous week, likely the result of potential homebuyers hesitant to purchase in this highly volatile and uncertain environment." The four-week moving average for the seasonally adjusted market index and the refinance index went up 6.9% and 10.1%, respectively, while the four-week moving average on the seasonally adjusted purchase index fell 2.2%. Home refinancings dominated last week, representing 78.8% of all applications, up from 75.6% a week earlier. The average contract interest rate for the 30-year, fixed-rate mortgage fell to 4.32%, down from 4.37% a week earlier, while the 15-year, FRM declined to 3.47% from 3.52%. Write to: Kerri Panchuk.