Read Wolff's article here.

Read Clemens's post here.

Excerpt:

In fact, the average African-trained member of the American Medical Association left his or her country of training well over five years after earning the Medical Doctor degree—as I learned when I surveyed them. Thus an African country that has invested in the training of a typical emigrant doctor has already received several years of service from that doctor (without even accounting for care provided during medical school). So it is false to say that the investment in the training of those people is fully “lost”. Furthermore, African-trained members of the American Medical Association send home to Africa, on average, over $6,000 per year, even 20 years after arriving in the United States—including those who send no money. Far from being “scant compensation”, this means that the typical African-trained doctor coming to the United States has sent back much more than the cost of training another doctor in the country he or she came from.

Read an academic paper on this topic here.