@Garfield M. Thank you for sharing this cmap link, it is fascinating to look at how each Chicago neighborhood has been evolving over the last 20 years.
Lots of interesting facts there. For example, I know Beverly is a very nice area but I did not realize 34% of the households make more then $150,000 year there. If accurate, that is more then double the Chicago average,so quiet amazing.
While other areas like Belmont Cragin are also very interesting. I thought that was an area that was always part of the gentrification conversation.
According to this data, however, back in 2000, Belmont Cragin was 28% white and 65% hispanic. In 2020 it is 14% white. 80% Hispanic.
Anyway , @Ryan Bird back to the migration question: as many pointed out, this would only matter if you are some big shot like Grant Cardone, looking to buy or build a 500 unit multifamily in a town with a population of 50,000 people. Net migration will not matter to your situation, if you are in a City with 2.7 million people, and you are looking to buy a 6 flat, you will still find tenants no problem, even if the city had a negative 20,000 net migration in the last 20 years.
Another thing that is misleading also is that many times developers are replacing the old housing stock like a 3 flat with a fancy single family home, so 10 peoples may leave the area as a result and 2 new people may be moving in. Net result will look like this area lost 8 more people. There is a difference between change in density versus peoples simply escaping an area due to high crime or property taxes. (The latter obviously also happens in parts of Chicago unfortunately).