These communities need not be walled - they have economic walls. First, they are far away from urban centers with no access by public transportation. There is no way to get there without automobiles. Such communities are moving farther and farther out; in the old days you used to be wealthy if you lived twenty minutes from downtown, now the truly wealthy live at least an hour away. Second, these communities spend large amount of money on police forces. Why would wealthy communities with no poverty need large amounts of police? It's not to keep them safe from their fellow residents, it's to keep them safe from outsiders. Anyone looking "suspicious" (i.e. poor or minority), is pulled over and harassed, and often served up with tickets costing hundreds of dollars. Finally, high housing prices make sure anyone not in the top ten percent of income earners cannot afford to live there, or anywhere even close.
And due to "local control" these communities can keep all their money and spend it on the best schools and public services, while poor communities face closed libraries, failing schools, deactivated streetlights, and roads turned back into gravel. This, in turn, decreases social mobility. It also leads to political balkinization, as districts of wealthy are gerrymandered to keep Republican politicians in power. That's the finding out of this report:
Middle-Class Areas Shrink as Income Gap Grows, New Report Finds (New York Times)
The findings show a changed map of prosperity in the United States over the past four decades, with larger patches of affluence and poverty and a shrinking middle.
In 2007, the last year captured by the data, 44 percent of families lived in neighborhoods the study defined as middle-income, down from 65 percent of families in 1970. At the same time, a third of American families lived in areas of either affluence or poverty, up from just 15 percent of families in 1970.
The study comes at a time of growing concern about inequality and an ever-louder partisan debate over whether it matters. It raises, but does not answer, the question of whether increased economic inequality, and the resulting income segregation, impedes social mobility.
Much of the shift is the result of changing income structure in the United States. Part of the country’s middle class has slipped to the lower rungs of the income ladder as manufacturing and other middle-class jobs have dwindled, while the wealthy receive a bigger portion of the income pie. Put simply, there are fewer people in the middle.
But the shift is more than just changes in income. The study also found that there is more residential sorting by income, with the rich flocking together in new exurbs and gentrifying pockets where lower- and middle-income families cannot afford to live.
ean F. Reardon, an author of the study and a sociologist at Stanford, argued that the shifts had far-reaching implications for the next generation. Children in mostly poor neighborhoods tend to have less access to high-quality schools, child care and preschool, as well as to support networks or educated and economically stable neighbors who might serve as role models.
The isolation of the prosperous, he said, means less interaction with people from other income groups and a greater risk to their support for policies and investments that benefit the broader public — like schools, parks and public transportation systems. About 14 percent of families lived in affluent neighborhoods in 2007, up from 7 percent in 1970, the study found.
The map of that change for Philadelphia is a red stripe of wealthy suburbs curving around a poor, blue urban center, broken by a few red dots of gentrification. It is the picture of the economic change that slammed into Philadelphia decades ago as its industrial base declined and left a shrunken middle class and a poorer urban core.
The Germantown neighborhood, once solidly middle class, is now mostly low income. Chelten Avenue, one of its main thoroughfares, is a hard-luck strip of check-cashing stores and takeout restaurants.