Published in May 2012, Foreign born scientists provides a first systematic study on the mobility of researchers in 16 countries across four fields - biology, chemistry, earth and environmental sciences, and materials. Data were collected from 17 182 respondents using a web-based survey during 2011 and show considerable variation across countries in both immigration and emigration patterns. The authors of the study employed a slightly different methodology  as opposed to conventional brain drain studies - for researchers in each country, they asked where they were at age 18, yielding data both on which countries rely on immigrant talent and on which countries are supplying that talent.

Some of the interesting results include:

• Switzerland has by far the greatest percentage of scientists from other countries (56.7 %), while India has the lowest (0.8%) followed closely by Italy and Japan
• The most likely reason to come to a country for postdoctoral study or work was professional (career growth, research environment, and funding opportunities)
• In diaspora rates, India heads the list with three in eight of those living in the country when they were 18 out of the country in 2011. On the other hand, Japan is on the opposite tail of the data.
• As for return rates, researchers from Spain were the most likely to return and those from India least likely.

The National Bureau of Economic Research