Wall Street falls amid global growth worries

U.S. stocks dropped Thursday as oil prices slid and worries about the global economy resurfaced, putting pressure on the dollar as investors fled riskier assets and sought safety in the yen and gold. "There's concern about a global slowdown," said Michael O'Rourke, chief market strategist at JonesTrading in Greenwich, Connecticut. "I think what we're seeing is the market believes that these (global central bank) policies and discussions on negative rates have diminishing returns at this point an