FRIEDRICH-EBERT-STIFTUNG 6 The concept of brain drain is used mainly by economists for macro-analyses of human capital transfer from developing to developed countries(for example, Boeri, Brücker, Docquier and Rapoport 2012). It provides a helpful framework for understanding highly qualified migration within the EU. Inter­national labour migration is characterised by positive selection (in other words, migrants have above-average skills; Chiswick 1999) and positive sorting(that is, highly skilled migrants tend to emigrate to countries where there is a high return to skills; Docquier and Rapoport 2012). This, in turn, leads to brain gain for the destination countries: they make use of immigrants’ qualifications, for whose acquisition they did not incur any costs, to offset labour shortages and boost their knowledge economy. From the perspective of the sending countries, on the other hand, highly qualified emigration implies brain drain: on one hand, they lose their»investment« in education and skills and, on the other hand, have to face a shortage of qualified workers. The cost of brain drain depends on the sectoral composition of highly qualified emigration, especially if the professions that are the most affected influence the production potential of others(such as health care professionals or engineers; Beine et al. 2008). Sending countries might nevertheless benefit from highly qualified emigration through remittances, transnational networks(Chiswick 2005) or knowledge transfer(Gibson and McKenzie 2012). Brain drain happens not only from developing to developed countries, but also between developed countries, such as between EU countries (Galgóczi, Leschke and Watt 2009). Highly qualified immigra­tion is indeed becoming an essential component of national technology and economic development policies in European and most other industrialised countries(Mahroum 2001: 27). This is leading to competition between countries to attract the brightest workers(Boeri et al. 2012). The extent to which the current intra-EU mobility of highly qualified workers can be equated with intra-EU brain drain and gain, however, remains an open question that has to be assessed empirically. 1.1.2 METHODOLOGICAL ISSUES IN EVALUATING INTRA-EU BRAIN DRAIN AND GAIN Investigating the presence of brain drain within the EU, ide­ally, requires considering the duration of the immigration of highly qualified workers: the concepts of brain drain and gain imply permanent or long-term immigration of highly qualified workers from economically less prosperous sending countries to the most prosperous destination countries. By contrast, a scenario of intra-EU mobility of highly qualified workers characterised by a fluidity of movement between sending and destination countries would provide evidence of an intra-EU »brain circulation«. Whether intra-EU mobility of highly qualified citizens contributes to the building of an integrated EU skilled labour market – the brain circulation scenario – or whether it leads to new forms of inequality between EU countries thus depends on the duration of the migration of intra-EU highly qualified immigrants: distinguishing between short- and long-term, as well as permanent immigration is essential for answering this question. This distinction between short- and long-term immigration is particularly relevant in the EU context because of the very low mobility constraints and costs for EU workers as result of the free movement rights and EU citizenship. Unfortunately, macro-level and cross-national population survey data only provide informa­tion on aggregate migration flows and stocks and do not enable the assessment of multiple and complex migration trajectories, which would be required to measure this phenomenon with confidence and precision. The analyses presented in this study can therefore only grossly approximate the significance of brain drain and brain gain within the EU. Moreover, and due to the limited comparability of the available data, in this study intra-EU brain drain and gain will be assessed by applying a broad definition of highly qualified workers: intra-EU highly qualified immigrants will be operationalised as EU citizens with a tertiary degree residing in an EU country that is not their country of citizenship. Such a broad definition has the advantage of being applicable to a wide range of national data and of providing more com­parable findings across national survey data for the country studies. Nevertheless, there are obviously many variations in the socio-economic profiles of citizens with a tertiary degree and in the migration plans and trajectories of highly qualified intra-EU immigrants that would affect the severity of brain drain and gain. Investigating the presence of intra-EU brain drain and gain ideally requires such a fine-grained analysis of the socio-demographic profiles of intra-EU immigrants. Unfortunately, this is beyond the scope of this study, whose aim is to provide a first overview of this issue in a selection of countries. Lastly, brain drain and gain can best be assessed by considering not only the immigration stock but also the immigration and emigration flows of highly qualified intra-EU immigrants. Intra-EU immigration stock refers to the total population of EU citizens residing in a different member state from their country of origin. By contrast, intra-EU immigration flow refers to the population of EU citizens who immigrate to another EU member state than their country of origin in a given year. In a similar vein, intra-EU emigration flow refers to the population of EU citizens who emigrated from their country of origin to another EU member state within a given year. Applied to the population of highly qualified workers, immigration stock provides information on the total population of highly qualified intra-EU immigrants, while immigration flow provides insights into the amplitude of this on-going process. The availability of the data required for assessing the extent of intra-EU labour mobility differs strongly for immigration stock, immigration and emigration flows. Intra-EU immigration stock is the easiest component to assess: general population surveys carried out by EU member states, such as the European Labour Force Survey(EU-LFS), are based on representative samples of the population resid­ing in a country. Such representative samples of the overall population therefore contain a subsample of non-national citizens – composed of EU and non-EU immigrants – that can be used for assessing immigrant stocks. Moreover, such surveys contain detailed questions on respondents’ education and socio-economic status. The analysis of general popula­tion surveys carried out by EU member states can thus shed light on the stock of highly qualified intra-EU immigrants. However, such general population surveys can provide data