Berry, R. Albert and Ronald Soligo (1969), "Some Welfare Aspects of International Migration." Journal of Political Economy, 77(5), 778-794.

EXCERPT:
"The welfare implications of factor flows between countries, unlike those of flows of goods, have received very little theoretical treatment to date. It is widely accepted that emigration of highly skilled people constitutes a loss to a country (Oteiza 1965, Perkins 1966) and fairly generally agreed that emigration of unskilled labor can improve the lot of the remaining populace. Yet these propositions are not self-evident."