A recent NBER working paper, “Internationalization of U.S. Doctorate Education,” takes a look at trends in doctoral degrees awarded by American institutions in the physical sciences, engineering, and economics.

From the abstract, “The representation of a large number of students born outside the United States among the ranks of doctorate recipients from U.S. universities is one of the most significant transformations in U.S. graduate education and the international market for highly-trained workers in science and engineering in the last quarter century.”

That transformation wouldn’t be possible without travel and visa allowances, as well as an educational and cultural atmosphere that es immigrants. The trend also speaks to the level of prestige and respect accorded to U.S. institutions and degrees, and the portability and value of those degrees abroad.