[chipsy]

Here's a real-world example of a mass migration occurring: German reunification. 20 years on, a disparity remains but both economies have grown substantially and towards parity, and the population figures have only shifted somewhat.[1] To some extent this is a best-case since there are other similarities among Germans, but it's an example of how it can go well.

[1] http://www.guardian.co.uk/world/2012/oct/09/west-east-german...