Important factors when interpreting bibliometric rankings of world universities: an example from oncology

This paper presents bibliometric characteristics of the 386 most frequently publishing world universities and of a (partly overlapping) set of 529 European universities. Rather than presenting a ranking itself, it presents a statistical analysis of ranking data, focusing on more general patterns. It compares US universities with European institutions; countries with a strong concentration of academic research activities among universities with nations showing a more even distribution; a ranking of universities based on indicators calculated for all research fields combined with one compiled for a single field (oncology); general with specialised universities; and rankings based on a single indicator with maps combining social network analysis and a series of indicators. It highlights important factors that should be taken into account in the interpretation of rankings of research universities based on bibliometric indicators. Moreover, it illustrates policy-relevant research questions that may be addressed in secondary analyses of ranking data. In this way, this paper aims at contributing to a public information system on research universities.