U.S home prices rose rapidly in May, a trend that is thwarting some would-be buyers and pulling down home sales.

The S&P CoreLogic Case-Shiller 20-city home price index rose 6.5 percent in May from a year earlier. That's down slightly from April, but is still more than double the increase workers are seeing in their paychecks.

Mortgage rates have also increased, pushing up monthly costs for home buyers even further. Sales of existing homes have fallen for three straight months after peaking in November. Pending home sales have also declined over the past year.

Still, home prices in some of the hottest real estate markets continue to move higher: Prices rose 13.6 percent in Seattle from a year earlier, 12.6 percent in Las Vegas and 10.9 percent in San Francisco.