"A lot of it had to do with the decline of heavy industry, which employed a lot of blacks and blue-collar whites, in a whole set of Rust Belt states, " he said.

CNN: Family roots lure many African-Americans back to South

The demolition of the Third Avenue Elevated subway line set off a building boom and a white-collar influx, most notably of young educated women who suddenly found themselves free of family, opprobrium, and, thanks to birth control, the problem of sexual consequence.

NEWYORKER: Looking for Someone

Majora Carter, who set up Sustainable South Bronx to help lift the area out of poverty by creating green-collar jobs, is frustrated by this difference between the European and American industries.

CNN: Green roofs cool cities, combat climate change, say Germans