# A Data appendix

Migration data presented in Section 3 follow Docquier et al. (2010) who construct comprehensive 195x195 matrices of bilateral migration stocks. These matrices cover the two skill groups (college graduates and less educated individuals), and two years (1990 and 2000). Migration is de...ned on the basis of country of birth which is time invariant (contrary to the concept of citizenship, which changes with naturalization) and independent of the changes in policies regarding naturalization. However, this de...nition does not account for whether education has been acquired in the home or in the host country. This induces a potential over-estimation of the intensity of the brain drain migration of children and students can represent an important fraction of total immigration for certain countries.<sup>17</sup> The methodology is described in detail in Docquier et al. (2010) and it consists of three main steps. The starting point (step 1) is the database described in Docquier, Lowell and Marfouk (2009) documenting bilateral migration stocks in OECD host countries. It is based on a collection of census and register immigration data by country of birth and educational level in the 30 OECD countries in 1990 and 2000. This OECD set of destinations does not include the three member states which joined the OECD in 2010 (Chile, Israel and Slovenia) and future members (Estonia and Russia). This database characterizes the education level, origin and destination of about 57.4 million migrants in 2000 and 40.8 million migrants in 1990. High-skill migration represents 35.4 percent of the total in 2000 (30.1 percent in 1990). The second step consists of a collection of similar immigration data from 46 nonOECD destinations in 2000 and 31 destinations in 1990. In the third step, data collected in steps 1 and 2 are used to estimate the determinants of the size of bilateral migration (Mijt<sup>s)from countryitocountryjintheeducationgroupsatyeart.Then,basedonthese</sup> estimations, the size of the migrant stock from each origin country to the remaining 119 non-OECD host countries in 2000 (and 134 in 1990) for each education level is predicted. The ...nal 195x195 database combines recorded migration stocks (when census and register data are available) and out-of-sample predictions (when o¢ cial statistics are missing).

Table A1 provides summary statistics for migration stocks which are comparable with labor force data. The database characterizes the origin, destination and education level of about 100.5 million adult migrants in 2000, and 80.2 million in 1990. Table A2 distinguishes observed and imputed values for immigrants to countries included in our sample. Table A3 shows stock of immigrants and emigrants in 1990 and 2000 as percentage of the skill-speci...c labor force. Table A4 describes the distribution of the labor force between college graduates and less educated as percentage of total.

> 17Beine et al (2007) have estimated the age-of-entry structure of high-skill immigration and proposed alternative measures of the brain drain excluding those who left their home country before age 12, 18 or 22. The corrected rates are obviously lower than those calculated without age-of-entry restrictions. However, the correlation between corrected and uncorrected rates is extremely high and the country rankings by brain drain intensities are basically una¤ected by the correction. This should mitigate concerns about children migration possibly leading to cross-sectional biases in the brain drain estimates.

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