Traders work on the floor of the New York Stock Exchange February 23, 2009. Wall Street plunged Monday with the Dow Jones average and the S&P 500 index dropping to a 12-year-low on concerns about dim economic outlook.

　　Traders work on the floor of the New York Stock Exchange February 23, 2009. Wall Street plunged Monday with the Dow Jones average and the S&P 500 index dropping to a 12-year-low on concerns about dim economic outlook.

　　A trader works on the floor of the New York Stock Exchange February 23, 2009. Wall Street plunged Monday with the Dow Jones average and the S&P 500 index dropping to a 12-year-low on concerns about dim economic outlook.