The average price of a single-family home inched higher in August with gains in most areas of the country, according to the Standard & Poor’s/Case-Shiller index. Both the 10-city composite index and 20-city index rose 0.2% in August from the prior month. The indices remain lower than a year ago, with the 10-city down 3.5% and the 20-city composite 3.8% lower than August 2010. “There was some weakness in the monthly statistics, as 10 of the cities post price declines in August over July,” said David Blitzer, chairman of the S&P index committee. “And even though the annual rates are largely improving, 18 MSAs and both composites are still negative.” Blitzer said there is a “modest glimmer of hope” in the fact 16 metropolitan areas experienced price gains in August from July. “The Midwest is one region that really stands out in terms of recent relative strength. Chicago, Detroit and Minneapolis have all posted very sharp monthly increases going back to May,” he said. Detroit with a 2.7% gain and Washington with a 0.3% increase were the only two metropolitan areas to see prices rise in August from a year earlier. Write to Jason Philyaw. Follow him on Twitter: @jrphilyaw.