Against the current of scientific researchers moving to universities and research institutes outside their home countries, there is also an observable flow of researchers who relocate back to their home countries following a foreign stay. The aim of this report is to take stock of conceptual and measurement issues related to this phenomenon, referred to as the “return mobility” of researchers. In the context of European policies striving to promote excellent research while realizing it by efficient spending, there are fears that researcher mobility towards centers of excellence (seen as “brain drain” in “net exporter” countries) further widens the gap between regions of Europe. This fear is behind a growing concern for fostering the return mobility of talented researchers to ensure a more equal distribution of research capacity.

The in-depth literature survey carried out in the framework of this study suggests that the very concepts of “brain drain” or “brain gain” are associated with a specific understanding of researcher mobility, which rests on rather strict assumptions that strongly influences the framing of research problems and policy interventions. This most widely diffused “allocative approach”, mainly based on economic neo-classical and general equilibrium-based models and concepts, conceptualizes researcher mobility under the assumptions that human capital, embodied in rational agents, is efficiently used by the productive system. The study shows that at least two other approaches may be distinguished. These approaches may be more aligned with how scientific research activity is carried out and how it is embedded in the socio-economic fabric. An eventual shift of focus from the “allocative” to the “connective” approach (which, based on evolutionary economics, conceives human capital as inherently networked, in a complex, evolving system) would point in the direction of changing the object of study. Rather than on the changing stock of researchers, it would focus on the heterogeneity of research actors and networks, the impact of reconfigurations of scientific, technological and social networks in which researchers’ work is embedded. As one of the case studies reviewed shows, a research system of a given country can substantially benefit from the establishment of new academic and social network connections due to a temporary mobility event even if the mobile researcher has physically “emigrated” from a given country. Alternatively, a focus on the “creativity” approach (which considers changes of contexts as inherent to creating the conditions for knowledge recombination) would lead to putting greater emphasis on the study of the evolution of ideas, research agendas and research careers. The possibilities for improving our knowledge regarding the role played by researcher mobility within the epistemic and organizational dynamics of the European Research Area are extensive, particularly if we do not only think of mobility as a re/allocative phenomenon.

The empirical section of the study provides evidence on country-level return mobility patterns of researchers, following the “allocative approach”, using data collected in the context of the MORE2 survey, a Study on Mobility Patterns and Career Paths of Researchers. Return mobility patterns are identified by highlighting differences across gender, discipline, seniority, country of citizenship as well as of PhD degree completion. To the possible extent, motivations for return mobility of researchers are also investigated, which highlight the importance of personal and family ties apart from academic ones. Potential alternative data sources are also examined, including the Career of Doctorate Holders Survey, the Labour Force Survey as well as novel “big data” sources, highlighting the limitations in the former and the vast potential in the latter. A final contrast of return mobility of researchers with the scientific and technological excellence of national research systems of destination countries presents a mixed picture, showing that countries on the entire spectrum of research excellence may experience high shares of returning researchers.