Prices of existing single-family homes rose by 3.2% in July, compared to the same month a year ago, according to the S&P/Case Shiller Home Price Index, which tracks prices in 20 major U.S. cities monthly. S&P released these data on Tuesday morning, Sept. 28.

A dozen of those 20 markets showed price increases over June, too. But July’s composite index, at 148.91, represents a slowdown in growth from the previous month: 0.6% compared to 1% in June over May. Sixteen of the 20 markets tracked showed weaker composite gains in July than in June. And on a seasonally adjusted basis, the 20-city composite index in July actually declined by 0.1% compared to June.

"While we could still see some residual support from the home buyers' tax credit, which covers purchases through Sept. 30, anyone looking for home prices to return to the lofty 2005-2006 might be disappointed," said David Blitzer, who chairs Standard & Poor's Index Committee, in a prepared statement. "Judging from the recent behavior of the housing market, stable prices seem more likely." 

Measured from the housing market's peak in June/July 2006 to July 2010, the 20-city index has fallen by 27.9%. But in recent months, the trend has been for the prices in most markets to level off.

Ten of the 20 cities tracked enjoyed year-over-year gains in July, and California led the charge, with home prices in San Francisco increasing by 11.2% to an index of 143.23; San Diego (9.3% to 165.02); and Los Angeles (7.5% to 176.27.) On the East Coast, Washington, D.C.’s recovery continued apace, as its index rose by 6.5% to 187.98.

Once again, Las Vegas had the dubious distinction of having the largest decline in home prices in July, when its index fell by 4.9% to 100.91 compared to July 2009. From the peak of the last housing boom to the present, Las Vegas’ home price index has dropped by 57%. The second-biggest loss occurred in Charlotte, N.C., where prices in July eroded by 3.5% to 117.03, from July 2009.

Because the S&P/Case Shiller Index focuses primarily on major metro areas, its indices typically show more dramatic home price changes than the Federal Housing Finance Agency (FHFA) home price index, which is based on the purchase prices of homes with loans owned or guaranteed by government-sponsored enterprises Freddie Mac and Fannie Mae in all 50 states. Last week, FHFA estimated that home prices in July were down 3.3% from July 2009, and fell by 0.5% from a revised June 2010 number.

John Caulfield is a senior editor for BUILDER magazine.

Learn more about markets featured in this article: San Francisco, CA, Las Vegas, NV, Los Angeles, CA, Charlotte, NC.