My understanding is that since Africa is connected to Europe by either land or a very small amount of water, you tend to get the same situation as Mexican immig

My understanding is that since Africa is connected to Europe by either land or a very small amount of water, you tend to get the same situation as Mexican immigrants into the US. You're optimizing more for risk-takers instead of wealth (which actually works pretty well with the US's culture, but might not in continental Europe). African immigrants to the US, on the other hand, tend to be quite wealthy/well educated. I think at one point Nigerian applicants for US citizenship were the most educated nationality. Presumably this is because the sheer cost of going there filters out a lot of people.