Professor of Economies, Columbia University, and Senior Research Staff, National Bureau of Economic Research. This paper is based, in large part, upon ongoing research in human capital at the National Bureau. This research is financed by grants from the Carnegie Corporation and from the Economic Development Administration of the United States Department of Commerce. I am grateful to Gary Becker, Barry Chiswick, and Victor Fuchs for helpful comments, and to Masanori Hashimoto and Sara Paroush for most competent assistance.