The potential gains, especially from freer immigration, are astounding.<p>&quot;The gains from eliminating migration barriers dwarf---by an order of a magnitude or two---the gains from eliminating other types of barriers. For the elimination of trade policy barriers and capital flow barriers, the estimated gains amount to less than a few percent of world GDP. For labor mobility barriers, the estimated gains are often in the range of 50–150 percent of world GDP.&quot; [1]<p>A typical example:<p>&quot;Take a male construction worker in the capital of Ghana. There isn’t much you could do to greatly raise his economic productivity in Ghana; access to better tools or training might make him modestly more productive. But if you let the exact same person emigrate to work at a construction site in any big U.S. city, his economic productivity would rise roughly 700% to 1,000%.&quot; [2]<p>[1] Clemens, Michael A. 2011. &quot;Economics and Emigration: Trillion-Dollar Bills on the Sidewalk?&quot; Journal of Economic Perspectives, 25(3): 83-106.
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