TAMPA - Tampa posted the fourth-largest annual home price decline among 20 metropolitan cities tracked in an S&P/Case-Shiller index released Tuesday.

On average, sale prices of existing homes in Tampa declined 6.7 percent in May, compared with the same month last year, according to the index. Miami, the only other Florida city in the index, had a 3.3 percent drop.

'Tampa and Miami are just beginning the downturn,' said Maureen Maitland, a vice president with S&P. 'Tampa had extremely high, double-digit increases for the past four years and saw its first decrease earlier this year.'

That's not to say, though, that the downturn will continue.

'We'll have to wait on the data to know for sure,' Maitland said.

Florida's relatively strong economy could keep home sale prices from dropping much lower, she said. Maitland pointed to Detroit - which saw the largest decrease, 11.1 percent - as an example of a city where home prices have consistently dropped during the past year.

Nationwide, home prices in the 20 U.S. cities fell the most in at least six years, suggesting the housing recession has yet to touch bottom.

Even so, the nationwide annual price decline was 2.8 percent, significantly lower than Tampa's. Behind Detroit, San Diego had the second-largest drop, down 7 percent, according to the report issued by Standard & Poor's and MacroMarkets LLC.

The declines indicate housing will continue to hamstring the U.S. economy, some economists say. A glut of unsold properties and mounting defaults are forcing builders to scale back construction and hindering consumer spending as homeowners are less able to borrow against home equity.

'Things are getting worse rather than better,' said Sal Guatieri, senior economist at BMO Capital Markets in Toronto. 'If home prices keep falling, eventually consumer confidence and spending will take a hit.'

Sales of new and previously owned homes fell to a 6.58 million annual pace in June, down 23 percent from their peak in 2005, according to reports last week. Inventories of unsold homes in June were at 4.7 million, close to a record. Housing starts in June were down 36 percent from their January 2006 peak pace of 2.29 million units.

Fifteen cities showed a year-over-year decrease in prices. But some cities showed an increase. Seattle, where prices rose 9.1 percent, had the biggest increases in home value, and Charlotte, N.C., was a runner-up with a 7 percent gain.

The S&P/Case-Shiller index and another gauge by the Office of Federal Housing Enterprise Oversight track individual homes through repeat sales and more accurately reflect price trends than the median prices reported by the government and National Association of Realtors, some economists say.

The Commerce Department and Realtors' price measures can be influenced by changes in the types of homes sold. Higher sales of cheaper homes relative to more-expensive properties will yield figures biased toward the low side.

Median new home prices fell 2.2 percent in June from a year earlier, while median existing home prices rose 0.3 percent, according to last week's reports from the Commerce Department and the National Association of Realtors.

A recovery in housing is being held back, in part, by a wave of subprime mortgage defaults, which is throwing homes back onto the market and prompting banks to tighten standards for borrowers with poor or limited credit histories. Mortgage lenders are feeling the pinch.

'We are experiencing home price depreciation almost like never before, with the exception of the Great Depression,' Angelo Mozilo, chief executive officer of Countrywide Financial Corp., said last week in a conference call after the biggest U.S. mortgage lender reported a 33 percent decline in second-quarter net income because of late loan payments.

Information from Bloomberg News was used in this report. Reporter Shannon Behnken can be reached at (813) 259-7804 or sbehnken@tampatrib.com.