Hi, assuming this question refers to cities in the USA like Detroit, there have been a few threads on the subjects of deurbanization, "white flight", red-lining, and so on. While you're waiting for answers here, you might be interested in checking these out:

• What led Detroit to the state it is in today? <-- includes links to loads more posts - check them out

• Is this Redditor's "Best-Of" comment about the history of Detroit accurate?