…are frickin’ huuuuge!
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.
In fact, existing estimates suggest that even small reductions in the barriers to labor mobility bring enormous gains. In the studies of Table 1, the gains from complete elimination of migration barriers are only realized with epic movements of people—at least half the population of poor countries would need to move to rich countries. But migration need not be that large in order to bring vast gains. A conservative reading of the evidence in Table 2, which provides an overview of efficency gains from partial elimination of barriers to labor mobility, suggests that the emigration of less than 5 percent of the population of poor regions would bring global gains exceeding the gains from total elimination of all policy barriers to merchandise trade and all barriers to capital flows.