(Reuters) - Traders work on the floor of the New York Stock Exchange February 7, 2012. REUTERS/Brendan McDermid

(Reuters) - Specialist Trader Frank Masiello (L) takes an order from trader Jonathon Corpina on the floor of the New York Stock Exchange, February 10, 2012. REUTERS/Brendan McDermid (UNITED STATES - Tags: BUSINESS)

(Reuters) - A trader works on the floor of the New York Stock Exchange February 10, 2012. REUTERS/Brendan McDermid (UNITED STATES - Tags: BUSINESS)

(Reuters) - A trader works on the floor of the New York Stock Exchange February 10, 2012. REUTERS/Brendan McDermid (UNITED STATES - Tags: BUSINESS)

(Reuters) - A trader works on the floor of the New York Stock Exchange February 10, 2012. REUTERS/Brendan McDermid (UNITED STATES - Tags: POLITICS BUSINESS)

(Reuters) - Italian Prime Minister Mario Monti (C) tours the floor of the New York Stock Exchange, February 10, 2012. REUTERS/Brendan McDermid (UNITED STATES - Tags: POLITICS BUSINESS)

(Reuters) - Italian Prime Minister Mario Monti prepares for an interview at the New York Stock Exchange February 10, 2012. REUTERS/Brendan McDermid (UNITED STATES - Tags: POLITICS BUSINESS)

(Reuters) - Italian Prime Minister Mario Monti (R) talks with specialist traders Michael Cacace (L) and Donald Civitanova (C) during a tour of the floor of the New York Stock Exchange, February 10, 2012. REUTERS/Brendan McDermid (UNITED STATES - Tags: POLITICS BUSINESS)

(Reuters) - Italian Prime Minister Mario Monti (R) is greeted by NYSE CEO Duncan Niederauer during a tour of the floor of the New York Stock Exchange, February 10, 2012. REUTERS/Brendan McDermid (UNITED STATES - Tags: POLITICS BUSINESS)

(Reuters) - Italian Prime Minister Mario Monti (L) is greeted by NYSE CEO Duncan Niederauer during a tour of the floor of the New York Stock Exchange, February 10, 2012. REUTERS/Brendan McDermid (UNITED STATES - Tags: POLITICS BUSINESS)

(Reuters) - Italian Prime Minister Mario Monti (C) tours the floor of the New York Stock Exchange, February 10, 2012. REUTERS/Brendan McDermid (UNITED STATES - Tags: POLITICS BUSINESS)

(AP) - FILE - In this Tuesday, Aug. 23, 2011 file photo, Bank of America Merrill Lynch traders work on the floor of the New York Stock Exchange in New York. There are fewer and fewer traders on the NYSE floor because of the dominance of computer trading of securities - including the high-frequency trading that can take advantage of price changes in a millisecond. Bank of America is the stock of the moment for high-frequency trading; investors use computer algorithms to exploit small changes in a stock's price. If a computer can seize on a stock like Bank of America a fraction of a second faster than the rest of the market, it can book a tiny profit. (AP Photo/Henny Ray Abrams)

(Reuters) - A Wall St. sign is seen outside the New York Stock Exchange, February 6, 2012. REUTERS/Brendan McDermid

(AP) - FILE - In this Oct. 10, 2011 file photo, musician Kanye West visits the 'Occupy Wall Street' protests in Zuccotti Park, New York. West was nominated for seven Grammy Awards. (AP Photo/Andrew Burton, file)

(Reuters) - Groupon CEO Andrew Mason poses with his newly married wife, pop musician Jenny Gillespie, outside the Nasdaq Market following his company's IPO in New York in this file photo taken November 4, 2011. Groupon reports its first results as a public company on Wednesday and the market will be keen to see if the largest daily deal website makes its first quarterly profit. REUTERS/Brendan McDermid/Files (UNITED STATES - Tags: BUSINESS ENTERTAINMENT)

(Reuters) - Employees and guests of Groupon ring the opening bell in celebration of the company's IPO at the Nasdaq Market in New York in this file photo taken November 4, 2011. Groupon reports its first results as a public company on Wednesday and the market will be keen to see if the largest daily deal website makes its first quarterly profit. REUTERS/Brendan McDermid/Files (UNITED STATES - Tags: BUSINESS)

(Reuters) - William P Stiritz, (L) chief executive officer of cereal maker Post Holdings, talks with specialist trader Peter Kennedy (R) of Getco Securities at the trading post that trades his company's stock on the floor of the New York Stock Exchange, February 7, 2012. REUTERS/Brendan McDermid (UNITED STATES - Tags: BUSINESS FOOD DRINK)

(Reuters) - William Stiritz, (R) chief executive officer of cereal maker Post Holdings, stands at the Getco Securities kiosk that trades his companies' stock on the floor of the New York Stock Exchange, February 7, 2012. REUTERS/Brendan McDermid (UNITED STATES - Tags: BUSINESS)

(Reuters) - Specialist traders work at the Getco Securities kiosk on the floor of the New York Stock Exchange February 7, 2012. REUTERS/Brendan McDermid (UNITED STATES - Tags: BUSINESS)

(Reuters) - A trader wears a New York Giants Superbowl hat on the floor of the New York Stock Exchange February 7, 2012. REUTERS/Brendan McDermid (UNITED STATES - Tags: BUSINESS)

(Reuters) - Traders work on the floor of the New York Stock Exchange, February 6, 2012. REUTERS/Brendan McDermid

(Reuters) - Specialist traders gather at the Getco Securities kiosk on the floor of the New York Stock Exchange, February 6, 2012. REUTERS/Brendan McDermid (UNITED STATES - Tags: BUSINESS)

(Reuters) - Traders work on the floor of the New York Stock Exchange, February 6, 2012. REUTERS/Brendan McDermid (UNITED STATES - Tags: BUSINESS)

(Reuters) - Traders gather at a post on the floor of the New York Stock Exchange February 3, 2012. REUTERS/Brendan McDermid

(Reuters) - Specialist trader Jason Hardzewicz (L) of Barclay's Capital gives prices to traders on the floor of the New York Stock Exchange February 3, 2012. REUTERS/Brendan McDermid

(Reuters) - A specialist trader watches his screen on the floor of the New York Stock Exchange, February 3, 2012. REUTERS/Brendan McDermid (UNITED STATES - Tags: BUSINESS)

(Reuters) - J.R. Smith (2nd L), CEO of AVG Technologies, looks up at the board on the floor of the New York Stock Exchange February 3, 2012. Smith and other executives of AVG Technologies rang the opening bell in celebration of the company's IPO on January 2. REUTERS/Brendan McDermid (UNITED STATES - Tags: BUSINESS)

(Reuters) - J.R. Smith, CEO of AVG Technologies (L), listens to trading specialist Michael O'Connor on the floor of the New York Stock Exchange February 3, 2012. Smith rang the opening bell in celebration of AVG Technologies which began trading on the NYSE January 2. REUTERS/Brendan McDermid (UNITED STATES - Tags: BUSINESS)

(Reuters) - Specialist trader Jason Hardzewicz (L) of Barclay's Capital gives a price to a trader on the floor of the New York Stock Exchange, February 3, 2012. REUTERS/Brendan McDermid (UNITED STATES - Tags: BUSINESS)

(Reuters) - A trader yells out prices during the Initial Public Offering of Greenway Medical Technologies Inc. on the floor of the New York Stock Exchange February 2, 2012. REUTERS/Lucas Jackson

(Reuters) - Specialist trader Frank Masiello (R) wears a New York Giants football jersey on the floor of the New York Stock Exchange February 1, 2012. Wall Street has long been known as a place for trying to one-up one another regardless of how mundane the event, so it's natural that the Super Bowl - the biggest U.S. sporting event of the year - becomes a big event for casual betting. REUTERS/Brendan McDermid (UNITED STATES - Tags: BUSINESS)

(Reuters) - A trader wears a New York Giants jersey on the floor of the New York Stock Exchange February 1, 2012. Wall Street has long been known as a place for trying to one-up one another regardless of how mundane the event, so it's natural that the Super Bowl - the biggest U.S. sporting event of the year - becomes a big event for casual betting. REUTERS/Brendan McDermid (UNITED STATES - Tags: BUSINESS SPORT FOOTBALL)

(Reuters) - A trader wears a New York Giants jersey on the floor of the New York Stock Exchange February 1, 2012. Wall Street has long been known as a place for trying to one-up one another regardless of how mundane the event, so it's natural that the Super Bowl - the biggest U.S. sporting event of the year - becomes a big event for casual betting. REUTERS/Brendan McDermid (UNITED STATES - Tags: BUSINESS SPORT FOOTBALL)

(Reuters) - Royal Caribbean's "Allure of the Seas" cruise ship enters its new home port in Fort Lauderdale in this November 11, 2010 file photo. Royal Caribbean Cruises Ltd, the world's second-largest cruise operator, warned that earnings in the current quarter could fall by as much as 50 percent as the Costa Concordia disaster off the coast of Italy caused a sharp drop-off in new cruise bookings. Royal Caribbean shares fell as much as 5.7 percent on Thursday morning but later pared losses to trade down 0.8 percent at $28.01 on the New York Stock Exchange. REUTERS/Joe Skipper/Files (UNITED STATES - Tags: DISASTER TRANSPORT TRAVEL MARITIME BUSINESS)

(Reuters) - Traders work at their terminals during the Initial Public Offering of Greenway Medical Technologies Inc. on the floor of the New York Stock Exchange February 2, 2012. REUTERS/Lucas Jackson (UNITED STATES - Tags: BUSINESS)

(Reuters) - Traders work on their personal terminals during the Initial Public Offering of Greenway Medical Technologies Inc. on the floor of the New York Stock Exchange February 2, 2012. REUTERS/Lucas Jackson (UNITED STATES - Tags: BUSINESS)

(Reuters) - Traders work on their personal terminals during the Initial Public Offering of AVG Technologies on the floor of the New York Stock Exchange February 2, 2012. REUTERS/Lucas Jackson (UNITED STATES - Tags: BUSINESS)

(Reuters) - Tommy Green (C), founder of Greenway Medical Technologies, watches the company's Initial Public Offering on the floor of the New York Stock Exchange February 2, 2012. REUTERS/Lucas Jackson (UNITED STATES - Tags: BUSINESS)

(Reuters) - Tommy Green, founder of Greenway Medical Technologies, watches the company's Initial Public Offering with his son and the company's CEO Wyche "Tee" Green (center L) on the floor of the New York Stock Exchange February 2, 2012. REUTERS/Lucas Jackson (UNITED STATES - Tags: BUSINESS)

(Reuters) - Tommy Green, founder of Greenway Medical Technologies, watches the company's Initial Public Offering with his son and company's CEO Wyche "Tee" Green (L) on the floor of the New York Stock Exchange February 2, 2012. REUTERS/Lucas Jackson (UNITED STATES - Tags: BUSINESS)

(Reuters) - Tommy Green, founder of Greenway Medical Technologies, watches the company's Initial Public Offering on the floor of the New York Stock Exchange February 2, 2012. REUTERS/Lucas Jackson (UNITED STATES - Tags: BUSINESS)

(Reuters) - Trader Dudley Devine works on the floor of the New York Stock Exchange, February 1, 2012. REUTERS/Brendan McDermid

(Reuters) - A trader wears a New York Giants jersey on the floor of the New York Stock Exchange, February 1, 2012. REUTERS/Brendan McDermid (UNITED STATES - Tags: BUSINESS SPORT FOOTBALL)

(Reuters) - A trader wears a New York Giants jersey on the floor of the New York Stock Exchange, February 1, 2012. REUTERS/Brendan McDermid (UNITED STATES - Tags: BUSINESS SPORT FOOTBALL)

(Reuters) - The Nasdaq Composite stock market index is seen inside their studios at Times Square in New York in this file image from April 1, 2011. Nasdaq OMX Group Inc's quarterly profit declined due to a number of expenses, but when stripping out the one-time charges, the Nasdaq stock market parent beat analysts' expectations, the company reported February 1, 2012. Picture taken April 1, 2011. REUTERS/Shannon Stapleton/Files (UNITED STATES - Tags: BUSINESS POLITICS)

(AP) - This undated picture made available by West Midlands Police on Wednesday Feb. 1, 2012, shows Mohammed Chowdhury, one of four British men radicalized by a U.S.-born Muslim cleric that pleaded guilty on Wednesday Feb. 1 to involvement in an al-Qaida inspired plot to spread terror and cause economic damage by bombing the London Stock Exchange at Christmastime. The men were among nine defendants facing trial in London over an alleged plot to attack the exchange and several other high-profile targets in December 2010. (AP Photo/West Midlands Police)

(AP) - This undated picture made available by West Midlands Police on Wednesday Feb. 1, 2012, shows Abdul Miah, one of four British men radicalized by a U.S.-born Muslim cleric that pleaded guilty on Wednesday Feb. 1 to involvement in an al-Qaida inspired plot to spread terror and cause economic damage by bombing the London Stock Exchange at Christmastime. The men were among nine defendants facing trial in London over an alleged plot to attack the exchange and several other high-profile targets in December 2010. (AP Photo/West Midlands Police)

(AP) - This undated picture made available by West Midlands Police on Wednesday Feb. 1, 2012, shows Gurukanth Desai, one of four British men radicalized by a U.S.-born Muslim cleric that pleaded guilty on Wednesday Feb. 1 to involvement in an al-Qaida inspired plot to spread terror and cause economic damage by bombing the London Stock Exchange at Christmastime. The men were among nine defendants facing trial in London over an alleged plot to attack the exchange and several other high-profile targets in December 2010. (AP Photo/West Midlands Police)

(AP) - This undated picture made available by West Midlands Police on Wednesday Feb. 1, 2012, shows Shah Rahman, one of four British men radicalized by a U.S.-born Muslim cleric that pleaded guilty on Wednesday Feb. 1 to involvement in an al-Qaida inspired plot to spread terror and cause economic damage by bombing the London Stock Exchange at Christmastime. The men were among nine defendants facing trial in London over an alleged plot to attack the exchange and several other high-profile targets in December 2010. (AP Photo/West Midlands Police)

(Reuters) - Traders work on the floor of the New York Stock Exchange January 31, 2012. REUTERS/Brendan McDermid