U.S. home values rose at a modest pace in December, a sign there are too few potential buyers to bid up prices. Real estate data provider CoreLogic says home prices rose 5 percent in December from 12 months earlier. That is down from the 5.5 percent price gain recorded in November. It’s much lower than the double-digit gains that occurred last year. Yet those much larger increases in early 2014 priced many potential buyers out of the market. Sales of existing homes actually slipped last year, after several years of gains. There is a bright side to the price slowdown, however: Smaller price increases, along with lower mortgage rates, may spur a rebound in sales this year. Just three states saw prices fall compared with 12 months earlier: Maryland, Vermont and Connecticut.