A gauge of the U.S. service sector fell in February to the lowest level in four months, with slower readings for employment and new business, Markit reported Monday. The index hit 52.7 in February, down from 56.7 in January. Readings above 50 indicate an expansion, with higher readings signaling faster expansions. "The unusually severe winter weather undoubtedly looks to have taken its toll on the economy in the first quarter," said Chris Williamson, Markit's chief economist.