1. Introduction
The establishment of research networks and the mobility of researchers across different countries, fields, and sectors have become a major policy objective in recent years (OECD, 2008; EC, 2012). Studies of mobile inventorsâ social capital show that links to the original location are maintained and that knowledge flows are deeply embedded in labor mobility (Agrawal, Cockburn, & McHale, 2006, 2011; Almeida & Kogut, 1999; Breschi & Lissoni, 2003). Thus, mobility generates positive spillovers among firms (Cooper, 2001; Møen, 2005), sectors (Crespi, Geuna, & Nesta, 2007; Zucker, Darby, & Brewer, 1998), academic institutions (Azoulay, Zivin, & Sampat, 2012), and countries (Hunt & Gauthier-Loiselle, 2010; Moser, Voena, & Waldinger, 2014). The evidence also shows that university scientists can increase their individual visibility and credibility by moving to a different academic environment and improving their performance, patterns of collaboration, and career development (Azoulay et al., 2012). Therefore, both the research system and the individual researcher can benefit from mobility.
Recent developments in the research system are demanding a better understanding of the consequences of mobility across locations, sectors, and career stages. First, globalization of the research community and increasing levels of international mobility (Auriol, Misu, & Freeman, 2013; Franzoni, Scellato, & Stephan, 2012; Moguerou & Di Pietrogiacomo, 2008) and collaboration (Glanzel, Debackere, & Meyer, 2008) are making the geographical mobility of researchers more relevant to an adequate flow of knowledge across locations. Second, the importance of improved knowledge transfer between research sectors (Gassmann, Enkel, & Chesbrough, 2010; Howells, Ramlogan, & Cheng, 2012; Powell, Koput, & Smith-Doerr, 1996) calls for a stronger emphasis on moves between public and private sectors. Third, the increased number of foreign PhD students and PhD graduates joining firms, and the greater number of fixed-term academic positions and the rapid diversification of academic work roles, are requiring a better understanding of the labor markets for researchers and the career consequences of mobility (Enders, 2005; Enders & Weert, 2004; Mangematin, 2000; Stephan, 2012; Zellner, 2003).
This chapter focuses on the mobility of academic researchers across locations, sectors, and career stages; its social relevance; and its consequences for researcher performance. We propose an approach to the analysis of researcher mobility that considers multiple mobility events throughout a researcherâs career (Eurobarometer, 2005). We start by reviewing the relevant literature on researcher mobility to understand its increasing importance, advantages, and disadvantages. We develop a typology of mobility events based on a life-course perspective, which allows us to present and select the more relevant mobility events during a researcherâs career. We also discuss the modeling difficulties (including selection bias, unobserved heterogeneity, and reverse causality) related to analyzing the effects of researcher mobility, and we suggest ways to overcome them.
2. Why Are We Increasingly Interested in Researcher Mobility?
Researchers have always moved across countries and sectors, and throughout their careers. Current research systems, however, are characterized by higher levels of internationalization and increased importance of intersector mobility and collaboration, as well as career diversification (temporariness and changes in work roles), all of which are making researcher mobility more significant to the development of the research system.
Data from the Organisation for Economic Co-operation and Development and the United Nations Educational, Scientific and Cultural Organization (UNESCO) Institute for Statistics (hereafter UIS) show a five-fold increase in foreign students worldwide between 1975 and 2012. Since 2000 alone their number has almost doubled (OECD, 2014),1 whereas in the United States, the number of international students has increased by 32% since 2000â2001 (Institute of International Education, 2012). The trend is similar in the United Kingdom, where the number of international students in research degree programs in UK higher education institutions increased threefold between 1994/1995 and 2012/2013.2 There is less precise and less comparable information available on the nationalities of research scientists. Moguerou and Di Pietrogiacomo (2008) show that the share of nonnational science and technology professionals without citizenship in the 27 countries of the European Union at that time increased from 1.6% to 2.4% in nine European member states between 2000 and 2006. An analysis of the mobility patterns of published authors listed on Scopus between 1996 and 2011 shows that the share of mobile authors differs among countries and regions. In Switzerland nearly 20% of authors have had a foreign affiliation, whereas in the rest of Western Europe the share is 12%, in Southern Europe it is 9%, and in the United States it is 7.4%; in China, Japan, and Brazil, however, this share is only 5% (OECD, 2013).3 The same study shows that the United States is the most internationally connected because it is the most important destination for researchers from other parts of the world (confirmed in Franzoni et al., 2012). In the United Kingdom, one of the European countries with a high level of internationalization, Higher Education Statistics Agency data show that in 2012/2013, 28% of research-active academic staff were of a non-UK nationality.
At the same time, an increasing share of researchers, especially among postdoctoral researchers, is leaving academia because of a lack of available academic positions (Stephan, 2012). For instance, in the United States about 37% of doctoral graduates are employed by private-sector firms; the shares are similar for Germany (39%) and the United Kingdom (32%).4 In Japan about 56% of all PhD students for whom destinations are known moved to take up positions outside of academia after graduating (NISTEP, 2009). Once doctorate holders join a specific sector following the completion of their PhD degree, they are primarily mobile within that sector, especially in countries with high-intensity research and development, such as Germany and the United States (OECD, 2014).
Within academia, there has been a greater shift toward employment with part-time and fixed-term contracts, particularly through an increase in positions financed by external grants. For example, in the United States the number of postdoctorates in scien...