Home prices in 20 U.S. cities rose at a slower pace than forecast in the year ended in April as declining affordability put a lid on appreciation.

The S&P/Case-Shiller index of property values increased 10.8 percent from April 2013, the smallest 12-month gain in more than a year, after rising 12.4 percent in March, the group reported Tuesday in New York. The median projection of 25 economists in a Bloomberg survey called for an 11.5 percent year-over-year increase in April.