Average home prices increased a seasonally adjusted 1.2% for February, according to a new S&P/Case-Shiller Home Price Index report (link opens a PDF) released today.

The report's larger 20-city composite index exceeded analysts' expectations for a 1% month-over-month improvement, and a 9.3% leap in year-over-year prices proved a pleasant 0.3 percentage point surprise above market predictions. According to the report, February's numbers mark the highest annual growth rate since May 2006.

This newest report also shows a slight increase in price growth over January's 1% month-over-month gains. But as National Association of Realtors Chief Economist Lawrence Yun suggested yesterday, recent price increases may be due more to lack of supply than to a more inherently valuable housing market. This is the first time since early 2005 that all 20 cities have experienced high seasonally adjusted prices for two consecutive months.

"Despite some recent mixed economic reports for March, housing continues to be one of the brighter spots in the economy," said S&P Dow Jones Indices Chairman of the Index Committee David Blitzer in a statement today. "The 2013 first-quarter GDP report shows that residential investment accelerated from the 2012 fourth quarter and made a positive contribution to growth. One open question is the mix of single family and apartments; housing starts data show a larger than usual share is apartments."

On a city-by-city basis, Phoenix continues to lead price leaps with a 23% jump over the past 12 months. San Francisco prices have increased 18.9%, and Las Vegas homes are 17.6% more expensive than in February 2012. All cities report positive price growth, but New York lags significantly with a 1.9% price gain.