Erik,

You use the mathematical approach in problem-solving.

Can you take the two extreme hypotheses?

First, let it be that there are no restrictions whatsoever in border crossing. Would it mean that, as Indi writes, all people from Sri Lanka would leave and the last would turn the light off? We can anticipate that countries perceived as the rich one, Norway, for example, would receive the influx of foreigners far above what they can engage in any reasonable productive activity, not to mention providing elementary surviving conditions. Locals would be upset, but let us say that these countries' governments would do nothing to stop new foreigners from coming. How many of them would survive the first winter living under the bridge?

The second hypothesis lets it be that practically no migration across the borders is allowed. Except for a very few cases as yours, for example, but with multiple restrictions. Can it be maintained? Or the whole world would become a mirror of the current situation in the United States, where we have 4% of the population living outside of the nation's legal texture?