So that is why it's good to let boat loads of Africans and Arabs on to the shores each day 
I merely explained the why.
I don’t know why each country has picked the immigrants it has but I assumed it might have something to do with future trade agreements. Here we have Indians, Chinese, Philippinos. The Americans are going with Mexicans. So it seems plausible trade relations might be playing a part.
One thing to note is white wealthy people are not migrating. So even if you want UK, American, Australian, we are not leaving our own country so it’s not an option. Meaning the selection for mass import of people means poorer nations.
I’m not sure what country you are in but it’s something you could email your cabinet minister about in regards to their criteria of immigrants.