Originally Posted by Dralcoffin
Those middle class neighborhoods were retreating and shrinking in size, immigration was basically over, the economy was battered, and the rot of the West and South Sides was picking up steam.
Firstly, immigration rates nationally and in Chicago increased
following the immigration liberalization of the late 1960s --- that's the period when Chicago began to develop it's remarkably large and strong Mexican community, with that immigration largely supplanting a spurt domestic migration from the American south that occurred during the 1950s which partially off-set suburban flight.
Also, I think you're making a key mistake in interpreting total population counts between censues, whether at the neighborhood level or for a city as a whole. An enormous part of population decline in Chicago has been from its adult residents having fewer and fewer children --- thus as older cohorts die out, there are fewer and fewer youth replacing them in the total population counts.
As of 1980 Chicago had about 850,000 residents under the age of 18, whereas now it has just over 600,000. This reduction in children, of course, not only covers most of the entire population drop since then --- it's indicative that the issue isn't so much one of flight
(i.e. people rushing for the exits) as it is an issue of lower population replacement
(namely, city residents as of 2010 not having as many children as city residents as of yesteryear, for whatever reason).
Big, big difference... though it definitely is still related to a variety of challenging factors stated such as jobs, schools, safety.