Data available in 2000. Regarding the situation in 2000, we estimate the total stock of adult immigrants in the OECD area at 58.496 million. The only country for which data on age, country of birth and educational attainment are missing is Mexico (0.493 million of immigrants). Data on immigrants’ age and educational attainment are not available for Japan, Iceland, Korea and Greece (2.030 million immigrants). However, the combination of European Council data and the European Labor Force Survey provides a good approximation of the Greek immigration structure (0.116 million adult immigrants). In the other 25 countries (55.974 million adult immigrants), Census and register data are (or will be) available. Adding Censuses and the Greek survey, we capture 56.090 million immigrants, i.e. 95.9% of the total. Finally, since about 1.8 million of those immigrants did not report their country of origin, we have accurate information on educational attainment and origin for 54.246 immigrant, i.e. 92.7% of the OECD adult immigration stock (to be compared with 44.1% in the US Census).

In the 26 countries (25 Census/Registers and Greece) where data on educational attainment will be available, we are usually able to work on the population aged 25 and over. However, this age limit is slightly di¤erent in some countries (18 in Switzerland, 15 in New Zealand, 13 in Poland). This should not distort our measure of the skilled immigration stock signi...cantly. Contrary to common belief, data on country of birth are available in a large majority of countries, even in European countries. The concept of citizenship must only be used for Germany, Italy, as well as for Greece (European Council data are based on the concept of citizenship), Japan and Korea.

Data available in 1990. The methodology is similar for 1990. To allow comparisons between 1990 and 2000, we consider the same number of receiving countries in 1990 (even if Hungary, Poland, ex-Czechoslovakia, Korea and Mexico were not members of the OECD). Our counterfactual 1990 OECD zone includes 29 countries (Slovakia and the Czech Republic were uni...ed). We estimate the total stock of adult immigrants in the OECD area at 39.844 million. Mexico is still the only country for which data on age, country of birth and educational attainment are missing (0.341 million immigrants). Data on immigrants’ age and educational attainment are not available in ex-Czechoslovakia, Hungary, Poland, Italy, Japan, Iceland, Korea and Greece (2.641 million immigrants). However, combining European Council data and the European Labor Force Survey provides a good approximation for Greece and Italy (0.646 million adult immigrants). In the other 20 countries (36.862 million adult immigrants), Census or register data are (or will be) available. Adding Censuses, Italian and Greek surveys, we capture 37.508 million immigrants, i.e. 94.1% of the total. About 2.1 million of those immigrants did not report their country of origin. We have accurate information on educational attainment and origin for 35.385 million immigrants, i.e. 88.8% of the OECD adult immigration stock (to be compared with 38.5% in the US Census).

In the 22 countries (20 Censuses/Registers, Italy and Greece) where data on 12