U.S. stocks ended lower on Thursday, with the Dow notching its biggest drop in nearly five months and falling below the psychologically key 10,000 level, after the leading NYMEX crude futures contract closed near the new high of $44.50 a barrel set earlier in the session. The Dow Jones industrial average was down 163.48 points, or 1.61 percent, to close unofficially at 9,963.03, based on the latest available data. The Standard & Poor's 500 Index was down 17.93 points, or 1.63 percent, at 1,080.70. The technology-laced Nasdaq Composite Index was down 33.43 points, or 1.80 percent, at 1,821.63.
