I don't see what we are arguing about. In the 1970-80's a large percentage of the center city's population fled to the suburbs to get away from "them". Since then, a significant part of the center city's black population has followed them out to the suburbs, and the whites they displaced have moved further out. Meanwhile, millennials are moving back into the city to reclaim areas like Uptown, Bucktown, Lincoln Park that 30 years ago were hellholes. Armitage and Sheffield in the 1960's was an absolute dump where you would be afraid to wait for the bus. I remember riding the L past Willow St and looking down at all the abandoned buildings and seeing a dead dog in the middle of the street. Look at it now! This is the natural cycle, where an area is colonized by the relatively wealthy, gets passed down to less and less wealthy until it becomes a dump, then gets re-colonized by the wealthy looking for a "deal".
Places like Calumet City, Dolton, South Holland are still on the downward part of the cycle. As for city depopulation, considering many more housing units are being demolished than being built, why is this a surprise? In the early 60's my girlfriend Samantha's family lived at 53rd and Peoria. We went back there a couple of years ago. There is a single house standing within two blocks. So in that square block, the population has gone down by what, 99%? Most of Englewood is like that. So is much of Austin. If there are no houses, chances are nobody lives there.
As a historical statement, in the mid-60's, when I started exploring, this is what I saw: the west side was black largely bound by Western on the east, the CNW on the north, Burlington on the south, Garfield Park on the west. South side was black south of 31st to about 79th, between the Rock Island and the IC, excluding 47th to 60th east of Washington Park (Hyde Park area). Black suburbs were East Chicago Heights, Robbins, Dixmoor, parts of Harvey, Chicago Heights east of the C&EI, and what was referred to as the Juneway Jungle, Howard to Juneway east of the L yards. That was about it. It might really surprise people today that on 9/28/69 the area around 95th/Dan Ryan was all white except for the projects west of the Ryan, even around 87th. South of South Shops was too.
Just some historical perspective...