The average price of a single-family home in the Standard & Poor's/Case-Shiller 20-city composite index edged up 0.6% in July from a month earlier. Data from the ratings agency's benchmark home price index showed prices inched up in 12 of the 20 largest metropolitan areas in July from the prior month. Prices appear to be leveling off somewhat as demand slows following the expiration of the homebuyer tax credit, which pulled tons of sales forward into the first half of this year. The 20-city composite index for July is up 3.2% from a year earlier, while the 10-city composite is 4.1% higher than the year ago and up 0.8% from June. "Home prices crept forward in July," said David Blitzer, chairman of the Standard & Poor’s index committee. "Ten of the 20 cities saw year-over-year gains and only one – Las Vegas – made a new bottom, as the impact of the first-time homebuyer program continued to fade away. While we could still see some residual support from the homebuyers’ tax credit, which covers purchases closing through September 30, anyone looking for home price to return to the lofty 2005-2006 might be disappointed." Home prices have risen steadily in San Diego for 15 months. Meanwhile, prices in Las Vegas slid another 0.6% in July from the month earlier to yet another low and have fallen in 44 of the past 46 months, according to Standard & Poor's, which bases the indices on closed sales contracts. Write to Jason Philyaw.