While many price reports have indicated an increase in home prices this summer, another price index suggests that the short ride may be over. The average sales price in the Altos Research 10-City Composite Index, a measure of home data in 10 major US metro regions, effectively bottomed out in January at $470,017, and climbed every month this year — including a July increase of 0.9% — until August, when it decreased 0.6%. Altos Research said it is a sign of an early start to the seasonally slow fall and winter months. The 10-City Composite Index was $506,180 in August. Average prices increased in only five of 26 major markets surveyed in August. “While lagging sources of housing market data are starting to report price increases, The Altos 10-City Composite Index now shows that the season spring buying season, and economic stimulus have run their course,” the report said. Inventory also declined in 22 of 26 major markets, lead by a 6.4% decrease in San Jose and a 5.1% decrease in San Francisco. The 10-City Composite Index inventory declined 2.6%. In San Diego, inventory increase 1.6%. Altos Research said the decrease was a positive sign as the housing market enters a slow season, since typically fewer borrowers participate in fall and winter months. The median number of days homes stayed on the market was above 100 days in all of the 26 markets except San Francisco. Miami had the longest median listing time of 251 days, more than eight months. Write to Austin Kilgore.