The number of U.S. mortgage refinancings (search) fell sharply last week suggesting that the refinancing boom may have run its course even as rates eased, economists said.

"The decline in the refinancing index suggests that we might simply be running out of consumers who want to refinance at these very low levels and makes another (refinancing) spike absent a drop in rates unlikely," Drew Matus, U.S. financial markets economist at Lehman Brothers (LEH) said in a research report on Wednesday.

The Mortgage Bankers Association (search) said its seasonally adjusted index on new refinancing applications fell by 14.2 percent to 1,949.2 for the week ended Oct. 8 from the previous week's 2,270.8, breaking a string of five consecutive weeks of increases in the refinancing index.

Last week marked the first time the refinancing index has fallen since the week of Aug. 27. The refinancing index is nearly 17 percent below its year-ago level of 2340.1.

The lower amount of refinancing applications came despite an ease in mortgage rates not seen since early March.

Thirty-year mortgage rates, excluding fees, averaged 5.69 percent, down 0.09 percentage point from the previous week and 0.12 percentage point lower than a year ago, the Washington trade group said.

"It may be underscoring that we have really run the course in terms of refinancing activity," said Michelle Girard, senior economist at RBS Greenwich Capital in Greenwich, Connecticut.

"It could be that rates have been so low for so long that everybody that is going to refinance has," she said.

The refinancing share of total new applications for last week was 44.5 percent, down from the prior week's 47.1 percent, the MBA said.

Overall, the MBA said its seasonally adjusted market index, a measure of mortgage activity, dropped 9.2 percent to 658.2 for the week ended on Oct. 8, down from the previous week's 724.8.

The association's purchase index, a gauge of new loan requests for home purchases, fell by 4.9 percent last week to 436.3 from 459.0 in the prior week.

The adjustable-rate mortgage share of last week's activity rose for the second week in a row to 34.9 percent of total applications from 33.9 percent the previous week, the group said.