Is there a relation between size and scientific performance of research groups? A Spanish university as a case study

An analysis of the performance of research groups from a bibliometric point of view is presented. We take into account the 258 research groups from the University of Murcia as a case study (excluding those from Humanities), in order to delve into the relationship between the size and the scientific performance of research groups, using absolute and relative bibliometric measures. Results point out that groups with more members show higher absolute values of production, visibility and impact as a consequence of their bigger size. Regarding relative indicators, we conclude that there is a statistically significant relationship between group size and the share of first quartile publications, as well as with the normalised citation impact. These results are determined by the Social Sciences area, where also per capita output is positively affected by group size. However, no statistical evidence has been found in the other areas regarding the possible influence of group size upon relative indicators. Finally, implications of these results for decision-making in research policy are discussed.