Might not be. The Nordic states seem rich enough already. Norway, for example, has a fund that makes all its citizens millionaires, so you do get richer if you join them. Can’t speak for Finland, but because it’s a welfare state you are going to get more than you give, at least until you start making serious money. I think they realise that immigration helps counter stagnation, especially if their population is aging and/or the birth rate is less than 2.
Norway is rich. They have oil. Their government is actually pretty decent with money also.
Sweden is an older country and has been historically pretty wealthy also.
Finland on the other hand... Well, we mostly have have trees and lakes. Our monetary policy consists of taking it up the behind from bigger countries, having sky high rates of taxes on everything, and finally, selling the few natural resources actually worth something to other foreign companies.
Norway is an extreme outlier due to their state controlled oil fund. You'd be better comparing them to Saudi Arabia than Finland. (Finland has no petroleum resources)
