The number of millionaires in the country's top ten metropolitan areas increased 17.5 percent in 2009, the highest growth rate in the last four years. According to Capgemini's 2010 U.S. Metro Wealth Index, New York City remains at the top of the list with the greatest number of millionaires (that means individuals with at least $1 million or more in investable assets, excluding primary residence, collectibles, consumable and consumer durables). In fact, Gotham is home to more millionaires than the next top three metro areas — Los Angeles, Chicago, and Washington D.C. — combined.

While many of the metro areas on the list maintained the same positions they held in 2008, Philadelphia and Boston switched positions, with Philly moving up to the number six spot and Boston slipping to seventh. Capgemini says that's because Philadelphia didn't feel the impact of unemployment or declines in real estate prices and per capita income as sharply as many other major cities did. Philadelphia now has about 104,000 millionaires while New York City lays claim to 667,000 wealthy individuals. Los Angeles, second on the list, is home to 236,000 millionaires.