Tracing scientific mobility of Early Career Researchers in Spain and The Netherlands through their publications

International scientific mobility is acknowledged to be a key mechanism for the diffusion of knowledge, particularly tacit or 'sticky' knowledge that cannot be transferred without geographical proximity and personal contact, for the incorporation of young researchers into elite transnational scientific networks, and for accessing additional resources or infrastructures that are essential to the research process but located in other places. The inadequacy and lack of appropriate data to assess the phenomenon of researcher mobility has been repeatedly pointed out by scholars and policy makers. This paper presents an exploratory analysis of different typologies of researchers according to their traceable mobility using scientific publications covered in the Web of Science (WoS). We compare two populations of researchers, of the same 'scientific age', based in Spain and The Netherlands. We observe differences in the degree of mobility of Spain and Netherlands based researchers. Factors associated with the different institutional conditions characterizing the two national systems need to be taken into account. First, the Spanish and Dutch university and research systems are different in many ways. Second, there may be very different institutional incentives for mobility in the two systems. More sophisticated bibliometric analyses and comparisons with different 'generations' of researchers, possibly combined with qualitative investigation, will be required to better understand the role and function of national institutional context in both research mobility and research careers.