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.
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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.
Reardon and Bischoff write:
Segregation of affluence not only concentrates income and wealth in a small number of communities, but also concentrates social capital and political power. As a result, any self-interested investment the rich make in their own communities has little chance of “spilling over” to benefit middle‐ and low-income families. In addition, it is increasingly unlikely that high‐income families interact with middle‐ and low‐income families, eroding some of the social empathy that might lead to support for broader public investment in social programs to help the poor and middle class.