Getting a visa to work in academia seems to be way easier than for private sector jobs. (I have ben working in academia in Europe and many people I know finished their PhD's and do postdocs in the states. One friend has changed to working in a company, but says it took nearly a year to get the paperwork sorted).

Another explanation:

More than 95% of people in the world are not American, and good American universities have access to the top talent. If the US is doing a competent job of hiring the best people then the majority of these researchers will not be American-born.

Or a counter explanation:

1. American colleges are still overwhelmingly the best in the world. https://en.wikipedia.org/wiki/Academic_Ranking_of_World_Univ...

2. 96% of students at American colleges are American. http://www.usnews.com/education/best-colleges/articles/2014/...

How does that explain the large numbers of foreign researchers?

Anecdotally, ~50% of the faculty in my department at a large American public university are foreigners. I've been told, but not verified, that if you count dual-citizens, that number gets closer to 65%.

Anecdotes are great.

Did some digging and found this article from 2012 which says that 38% of researchers in the U.S. are foreigners.

http://www.nature.com/news/global-mobility-science-on-the-mo...

> I've been told, but not verified, that if you count dual-citizens, that number gets closer to 65%.

Why on earth would you group dual citizens in the same category as foreigners?

Even if 100% of the faculty are dual citizens (Americans + something else), it would still be 100% American.

Because realistically, most of those dual citizens started out as foreigners and were eventually naturalized as a consequence of pursuing an academic career in the US.

My guess would be that a large number of dual citizens obtained their citizenship in the course of their scientific work. It speaks to the training problem we have.

Because many foreign cultures value education more than the U.S., overall.