These days, it seems, you need a college degree just to live in or around New York City. Almost 5 million people over the age of 25 in the New York metropolitan area — more than a third of the region’s population — had at least a bachelor’s degree in 2005, according to the latest data from the Census Bureau. In Manhattan, nearly three out of five residents were college graduates and one out of four had advanced degrees, forming one of the highest concentrations of highly educated people in any American city. The degree-holders are rapidly displacing the dropouts,...