Service businesses, which employ roughly 80 percent of American workers, grew more slowly in February and their workforces contracted for the first time in more than two years, according to a survey of executives, MarketWatch reported. The Institute for Supply Management said its non-manufacturing index dropped to 51.6 percent last month from 54 percent in January. The index, based on a survey of senior executives who buy supplies for their companies, shows that retailers, health care suppliers and hotels stumbled in February. Unusually poor weather was partly, but not entirely, to blame.