The S&P Case-Shiller index of home prices in the 20 largest markets showed a month-to-month increase of 1.6% in July. For the third month in a row, all 20 cities posted gains. Had prices not dropped in a single market (Detroit) last April, this month would have made it four in a row of across-the-board gains.

The Case-Shiller index compares current sales of single-family houses with previous sales. Newly-constructed houses are not included, neither are condos and co-ops. An attempt is made to count only "arm's length" transactions. This would include regular foreclosures and short sales, but not for example a home that is sold to a family member at a favorable market price. The index is compiled as a three-month moving average, and the data lags by two months.

On an annual basis, overall prices were up 1.2% from July 2011, the largest year-over-year gain in two years. Sixteen of the 20 cities covered by the Case-Shiller index had annualized gains.  In Phoenix, prices are up over 16% from a year ago. Prices fell from the previous year in Atlanta, Chicago, New York, and Las Vegas.

The largest increases could be occurring in the lower-end market. In a New York Times article "Home Prices Rise Again, This Time on the Low End", authors Shaila Dewan and Nelson D. Schwartz cite claims that valuations in the lowest tier have been rising more than twice as fast as the mid and upper tiers. An uptick in consumer confidence, historically low mortgage rates, and generally improved affordability are bringing back sidelined buyers in that category.

CNBC reports that billions of dollars have returned to home equity as a result of the recent value appreciation. In the first half of the year, 1.3 million homes that were previously "underwater" (worth less than the mortgages on them) have now turned positive.

David Blitzer of S&P Dow Jones, expresses the opinion shared by many industry analysts: "The news on home prices in this report confirms recent good news about housing. Single family housing starts are well ahead of last year’s pace, existing home sales are up, the inventory of homes for sale is down, and foreclosure activity is slowing."