Research performance analysis in physics - The Leiden example

We feel that bibliometric performance indicators are very useful in past-performance analysis of fields like physics and astronomy. Interviewed researchers stated that a ranking of research groups on the basis of the citation-per-publication ratio corresponds generally with their perception on the impact of these research groups. Those on top of ranking are active in their fields and perform research of high quality. However short-term indicators should be completed with citation-based measures indicating the impact of publications over a longer period of time. As a result of the application of bibliometric indicators, interesting factors due to communication practices and to types of research (for example, the role of fashionable research subjects) are identified. A very interesting point is the comparison of peer's expectations in an earlier stage with updated bibliometric results later on. We have presented in this paper a few examples. Our general conclusion is that bibliometric performance indicators provide for a field like physics (and astronomy as well) a useful instrument for research management and science policy.