Scale-Independent Bibliometric Indicators

Van Raan (this issue) makes an excellent case for using bibliometric data to measure some central aspects of scientific research and to construct indicators of groups: research groups, university departments, and institutes. He claims that, next to peer review, these indicators are indispensable for evaluating research and can be used in parallel with peer review processes. By way of an example, van Raan provides a table containing nine indicators for a German medical research institute. Two of these indicators—articles (P) and citations (C)—are established proxy measures for the size of a group and the impact of its published research (Katz & Hicks, 1997). The ratio between citations and articles (CPP) and the ratios between CPP and the mean Journal Citation Score and between the field-based world average and the Germany-specific world average—which are uniquely defined CPP reference values—are used to construct a set of indicators that van Raan suggests can be used to assess international research performance. This commentary focuses solely on the use of bibliometric indicators to compare international research performance. It addresses the fundamental question of whether CPP or measures like CPP can be used to accurately compare the performance of groups of different sizes.