No, what happened is that people moved to the cities 50 or more years ago from the south because there were good jobs to be had and more opportunities. Eventually the jobs left, but the people stayed. That's also why immigrants moved to the cities in years past, and now many are bypassing the cities in favor of the suburbs or factory farms where there are jobs.
In the 40's in NYC (where I lived for 50+yrs.) politicians exhorted Puerto Ricans to come there and escape the poverty of the island. The generous welfare system was a major factor. During the 60's and 70's another migration of blacks from the South took place. At that time, the jobs were aldready leaving, so the only incentive was welfare.