# 2 How big is the brain drain?

There is clear evidence that the brain drain has increased dramatically since the 1970s, both in absolute and relative terms. Nearly 30 years ago, the United Nations estimated the total number of highly-skilled South-North migrants for 1961-72 at only 300,000 (UNCTAD, 1975); less than a generation later, in 1990, the U.S. Census revealed that there were more than 2.5 million highly educated immigrants from developing countries residing in the U.S. alone, excluding people under the age of 25 (that is, without counting most foreign students). Country studies commissioned by the International Labor Organization also show that nearly 40% of the Philippines’ emigrants are college educated, and, more surprisingly, that Mexico in 1990 was the world’s third largest exporter of college-educated migrants (Lowell and Findlay, 2001). Since 1990, the chief causes of the brain drain have gained in strength and these increasing trends have been con...rmed. Indeed, selective immigration policies ...rst introduced in Australia and Canada in the 1980s have spread to other OECD countries: the Immigration Act of 1990 as well as the substantial relaxation of the quota for highly skilled professionals (H1-B visas) in the US constitute a very signi...cant change in the immigration policy of the country that remains the destination of about 40% of the immigrants to the OECD area. Finally, a growing number of EU countries (including France, Germany, Ireland and the UK) have recently introduced similar programs aiming at attracting a quali...ed workforce (e.g., through the creation of labor-shortage occupation lists) (OECD, 2002).

Until very recently, there were no comparative data on the magnitude of the brain drain. The ...rst serious e¤ort to put together harmonized international data on migration rates by education level is due to William Carrington and Enrica Detragiache from the International Monetary Fund, who used US 1990 Census data and other OECD statistics on international migration to construct estimates of emigration rates at three education levels (primary, secondary and tertiary schooling) for about 60 developing countries.<sup>2</sup> The Carrington-Detragiache (henceforth CD) estimates, however, su¤er from four main shortcomings. First, CD assumed for each country that the skill composition of its emigration to non-US OECD countries is identical to that of its emigration to the US; for example, Nigerian immigrants in the UK are assumed to be distributed across educational categories in the same way as Nigerian immigrants in the US. Consequently, the CD estimates are not reliable for countries for which the US is not the main destination. Second, at the time CD conducted their study, the OECD immigration data (regarding the EU, Japan, Switzerland, New Zealand...) did not allow for a full decomposition of the immigrants’ origin-mix; more precisely, the OECD published statistics indicating the country of origin only for the top 5 or 10 sending countries. For small countries not captured in these statistics, the ...gures reported in the CD data set are therefore biased: the

> 2See Carrington and Detragiache (1998, 1999). Relying on the same assumptions, Adams (2003) provides estimates for 2000.

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