Home prices held their ground in many metropolitan areas in May, according to the S&P/Case-Shiller indices released Tuesday. Nineteen of 20 markets tracked by Case-Shiller showed positive growth, with Minneapolis reporting the highest monthly increase at 2.8%. Only Las Vegas declined, with a -0.5% slip.

With such broad-based, although small, gains, both Case-Shiller’s 10-city and 20-city composites showed improvements.

The 10-city index, which includes Boston, Chicago, Denver, Las Vegas, Los Angeles, Miami, New York, San Diego, San Francisco, and Washington, posted a 1.2% monthly gain and a 5.4% annual jump. The 20-city composite, which incorporates the 10 cities above as well as Atlanta, Charlotte, Cleveland, Dallas, Detroit, Minneapolis, Phoenix; Portland, Ore.; Seattle, and Tampa, reported a 1.3% monthly increase and a 4.6% annual gain.

While growth, even small growth, certainly is better news than declines, David Blitzer, who is chairman of Standard and Poor’s index committee, reminded number-watchers to keep perspective. “While May’s report on its own looks somewhat positive, a broader look at home price levels over the past year still do not indicate that the housing market is in any form of sustained recovery,” he said. “Since reaching its recent trough in April 2009, the housing market has really only stabilized at this lower level.”

May’s gains may be due to common seasonal home buying patterns and the effects of the housing tax credit, which just expired April 30. “We need to watch where the housing markets will go after these temporary stimuli go away. June’s existing and new-home sales and housing starts data do not show much improvement in those statistics either. It still looks possible that the housing market might bounce along the bottom for the foreseeable future, before showing any real improvement that will filter through to the rest of the economy.”

In terms of annual numbers, the top two performing markets were coastal. San Francisco notched an 18.3% year-over-year gain, followed by San Diego, with a 12.4% improvement. The next-best? Minneapolis, with an 11.6% increase.

The worst decline came from Las Vegas, where home prices have declined by 6.5% over the past 12 months.

Alison Rice is senior editor, online, at BUILDER magazine.

Learn more about markets featured in this article: San Francisco, CA, San Diego, CA, Las Vegas, NV, Minneapolis-St. Paul, MN.