Adult immigrants will benefit less from the system than locals over their lifetime, but may end up contributing as much. Adult immigrants with advanced degrees who come to work here for a few years and then move out are penalized quite severely by the tax system, to the point where I think it makes very little sense to do that.
On my locally quite high $80k annual income (STEM PhD, 40yo), my employer pays an additional $36k in taxes and pension. Then I pay $22k in income taxes and 25% VAT on everything I buy.
Why would anyone with an advanced degree from China, India or the U.S. come to work here? Lowering the taxes for a couple of years following immigration, possibly proportionally to level of education, would encourage immigration and would be ethically defensible.
