The paper discusses definitions of mobility, the choice of unit of observation for mobility (establishment or enterprise) and classifications of sectors of the economy. The rationale for the discussion is to find a good basis for using mobility research to investigate flows of human capital in an innovation system. Consequences are then illuminated using Danish and Finnish data. These aspects of measurement are of interest because they illuminate important consequences of methodological choices related to the use of matched employee/employer register datasets, since the use of these in mobility research is in its infancy. These methodological considerations are the output of a Nordic project which is dealing with the flow of human capital through job mobility in general, through researcher mobility in particular, and through migration between the Nordic countries. The project is jointly undertaken by STEP, The Danish Institute for Studies in Research and Research Policy, Statistics Finland, Statistics Iceland, and Vinnova.
