THE INFLUENCE OF INTERNATIONAL COLLABORATION ON THE IMPACT OF RESEARCH RESULTS - SOME SIMPLE MATHEMATICAL CONSIDERATIONS CONCERNING THE ROLE OF SELF-CITATIONS

There is an ongoing discussion on the influence of international colla boration on impact as measured by citation-based indicators. Collabora tion generally involves more authors than 'no collaboration' work and it is obvious that the phenomenon of self-citation will be stronger (t here are more authors to cite themselves). Thus it can be seen as an i mportant amplifier' of measured impact. Although this effect is certai nly possible and already demonstrated recently, it should not be consi dered as the only or even major explanation of higher impact in the co mparison between 'no collaboration' and international collaboration. U sing data of an extensive bibliometric study of astronomical research in the Netherlands, we prove that higher rates of self-citation in int ernational collaboration do not play any significant role as 'impact a mplifier'. The central point is that proper impact measurement must in volve corrections for self-citations.