Those who only read the New York papers could be forgiven for thinking that almost all of the nation's rich live within a 10-block area on the Upper East Side or along a single stretch of Round Hill Road in Greenwich, Conn. New Yorkers see so much wealth around them, they figure that it has to have the most rich people in the country, if not the world. But they're wrong. According to a new study by TNS, the research company, Manhattan's number of millionaire households doesn't even rank among the top 10 counties in the country. (I know, not all millionaires in Manhattan are official residents of New York. But even subtracting...