Another argument against the brain drain hypothesis is that bringing talented workers to the “frontier” countries will boost the supply of global public goods. Rui Xu, in her job market paper from Stanford (pdf), considers exactly this effect. Here are her main results:
Science and engineering (S&E) workers are the fundamental inputs into scientific innovation and technology adoption. In the United States, more than 20% of the S&E workers are immigrants from developing countries. In this paper, I evaluate the impact of such brain drain from non-OECD (i.e., developing) countries using a multi-country endogenous growth model. The proposed framework introduces and quantifies a “frontier growth effect” of skilled migration: migrants from developing countries create more frontier knowledge in the U.S., and the non-rivalrous knowledge diffuses to all countries. In particular, each source country is able to adopt technology invented by migrants from other countries, a previously ignored externality of skilled migration. I quantify the model by matching both micro and macro moments, and then consider counterfactuals wherein U.S. immigration policy changes. My results suggest that a policy – which doubles the number of immigrants from every non-OECD country – would boost U.S. productivity growth by 0.1 percentage point per year, and improve average welfare in the U.S. by 3.3%. Such a policy can also benefit the source countries because of the “frontier growth effect”. Taking India as an example source country, I find that the same policy would lead to faster long-run growth and a 0.9% increase in average welfare in India. This welfare gain in India is largely the result of additional non-Indian migrants, indicating the significance of the previously overlooked externality.
In other words, the brain drain argument is overrated. You might also wish to sample our MRUniversity video on the brain drain argument.