Michael Rubens Bloomberg (born February 14, 1942) is an American businessman, politician and philanthropist. Since 2002, he has been the Mayor of New York City and, with a net worth of $18.1 billion in 2011, he is also the 13th-richest person in the United States. He is the founder and eighty-eight percent owner of Bloomberg L.P., a financial news and information services media company.
A lifelong Democrat before seeking elective office, Bloomberg switched his registration in 2001 and ran for mayor as a Republican, winning the election that year and a second term in 2005. Bloomberg left the Republican Party over policy and philosophical disagreements with national party leadership in 2007 and ran for his third term in 2009 as an independent candidate on the Republican ballot line. He was frequently mentioned as a possible independent candidate for the 2008 presidential election, which fueled further speculation when he left the Republican Party. There was also speculation that he would run as a vice-presidential candidate. Bloomberg did not, however, seek the presidency nor was he selected as a running mate by any of the presidential candidates.
In the fall of 2008, Bloomberg successfully campaigned for an amendment to New York City's term-limits law, in order to allow him to run for a third term in 2009. Bloomberg won the election on November 3, 2009.