Wall Street plummeted on Thursday as concerns over European debt problems and U.S. economic downturn spurred broad sell-off. Big banks were hit most because of more exposure to the European debt, leading the declines in the market. Dismal economic data added to losses as investors worried the U. S. economy was in danger of a double-dip recession. The Labor Department said on Thursday that the number of people applying jobless benefits rose 9,000 to 408,000 last week, worse than economists had expected. The department also reported that the CPI rose 0.5 percent in July, the largest gain since March, after falling 0.2 percent in June, which sparks worries of stagnation. Even worse, the Philadelphia Federal Reserve Bank said its business activity index dropped to minus 30.7 from positive 3.2 the month before, far below expectation. The Dow Jones Industrial Average plunged 419.63 points, or 3.68 percent, to 10,990.58. The Standard & Poor\'s 500 tumbled 53.24 points, or 4.46 percent, to 1,140.65. The Nasdaq Composite Index nosedived 131.05 points, or 5.22 percent, to 2,380.43.