Area and U.S. home prices were up modestly in May compared with a year ago, according to the Standard & Poor's/Case-Shiller index, but an economist said it could be several more months before prices improve enough to affect the economy.

Dallas-Fort Worth home prices rose 2.9 percent in May, the seventh month of gains compared with a year earlier, according to the closely watched index, released Tuesday. On average, home prices were up 4.6 percent in the 20 U.S. metropolitan areas recorded in the index.

Area home prices have posted year-over-year gains since November, when they rose 1.4 percent. In January, the annual gain peaked at 4.1 percent. Since then, home prices have continued to show gains, but the increase has been smaller each month.

Compared with the month before, area home prices were up 1.5 percent in May, less of an increase than the 2 percent in April over March.

Nationally, 13 of the 20 metro areas surveyed saw increases in May from a year earlier. The biggest gains were in San Francisco, up 18.3 percent; San Diego, 12.4 percent; and Minneapolis, 11.6 percent.

Prices declined the most in Las Vegas, which posted a 6.5 percent drop in May from a year ago.

"While May's report on its own looks somewhat positive, a broader look at home price levels over the past year still does not indicate that the housing market is in any form of sustained growth," said S&P economist David Blitzer. "The last seven months have basically been flat."

U.S. home prices have risen 5.1 percent from their April 2009 bottom. But they remain 29 percent below their July 2006 peak.

Blitzer said analysts are still evaluating the impact of the first-time home-buyer federal tax credit, which continues to apply to pending home sales that were under contract by April 30.

Sandra Baker, 817-390-7727

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