NB Huge generalization here - As I see it, in regards to immigration, if you exclude the one's fleeing from war/persecution (who might go back if things change, where they came from).

You have two types of migrants - the economic and the ambitious. The economic are typically poorly educated, rural people with little to no prospects where they come from. The ambitious are the bright middle-class, who due to class systems, corruption and various other factors can't see a way up in their society, so immigration could seem a better option. 
Every country likes most of the ambitious and has problems with some of the economic migrants.