From the New York Times:
For years now, people have been talking about the insulated world of the top 1 percent of Americans, but the top 20 percent of the income distribution is also steadily separating itself — by geography and by education as well as by income.
This self-segregation of a privileged fifth of the population is changing the American social order and the American political system, creating a self-perpetuating class at the top, which is ever more difficult to break into.
In hard numbers, the percentage of families with children living in very affluent neighborhoods more than doubled between 1970 and 2012, from 6.6 percent to 15.7 percent.
At the same time, the percentage of families with children living in traditional middle class neighborhoods with median incomes between 80 and 125 percent of the surrounding metropolitan area fell from 64.7 percent in 1970 to 40.5 percent.