I've simplified a bit but not really.
Right now every nation juices its GDP numbers using immigration numbers to substitute for population growth.
Remove the count of immigrants from "population growth", and watch every single nation reverse course on immigration.
Heres the full explaination:
https://www.worldometers.info/gdp/what-is-gdp/Immigration pushes up consumption and 'income', as well as government spending.
Remove the immigrant population from the equation, and there is no longer
a financial excuse for bringing in immigrants into any nation.
There doesn't seem to be anything here yet