Solid sales pushed up U.S. home prices at a steady pace in August from a year earlier, a sign that the housing market is improving despite a slowdown in the overall economy.

The Standard & Poor's/Case-Shiller 20-city home price index rose 5.1 percent in the 12 months ending in August, up from a 4.9 percent pace in July.

Home prices have risen at a 5 percent pace for most of this year, which economists see as more sustainable than last year's double-digit gains. Three years of solid hiring and historically low mortgage rates have enabled more Americans to buy homes. That's lifted sales of existing homes nearly 9 percent in the past year.

San Francisco and Denver both reported annual price gains of 10.7 percent, the largest of any city.