U.S. stock funds lost ground, falling 1.02% on average in the week ended Jan. 29, according to Lipper Inc. It was the fifth weekly setback in the past six weeks for U.S. diversified stock mutual funds. And it put their year-to-date loss at 1.38%. U.S. stocks fell amid stock market news about falling oil prices. Investors worried that they were a sign of slowing demand overseas.