The share of U.S. applications to refinance an existing home contracted to its smallest in 9-1/2 years last week as 30-year home borrowing costs climbed to their highest in more than four years, the Mortgage Bankers Association said on Wednesday.

The refinance share of mortgage applications in the week ended March 9 shrank to 40.1 percent of all applications, the slimmest proportion since September 2008 at the height of the global credit crisis.

This compared with 41.8 percent the previous week, the Washington-based industry group said.

The Market Composite Index, a measure of mortgage loan application volume, increased 0.9 percent on a seasonally adjusted basis from one week earlier.

The average contract interest rate for 30-year fixed-rate mortgages with conforming loan balances ($453,100 or less) increased to its highest level since January 2014, 4.69 percent, from 4.65 percent.

The average contract interest rate for 15-year fixed-rate mortgages decreased to 4.07 percent from 4.11 percent.