Fractional counting of citations in research evaluation: A cross- and interdisciplinary assessment of the Tsinghua University in Beijing

In the case of the scientometric evaluation of multi- or interdisciplinary units one risks to compare apples with oranges: each paper has to be assessed in comparison to an appropriate reference set. We suggest that the set of citing papers can be considered as the relevant representation of the field of impact. In order to normalize for differences in citation behavior among fields, citations can be fractionally counted proportionately to the length of the reference lists in the citing papers. This new method enables us to compare among units with different disciplinary affiliations at the paper level and also to assess the statistical significance of differences among sets. Twenty-seven departments of the Tsinghua University in Beijing are thus compared. Among them, the Department of Chinese Language and Linguistics is upgraded from the 19th to the second position in the ranking. The overall impact of 19 of the 27 departments is not significantly different at the 5% level when thus normalized for different citation potentials.

Research highlights
► This study first applies fractional counting of citations to assess performance of research units with different disciplinary identities.
► Departments of a leading university of China, the Tsinghua University were chosen for the study.
► We distinguish among 27 departments in different disciplines and show that this correction for the in-between field variation changes the rank order in important respects.
► The Department of Chinese Language & Literature which is ranked on the 19th position (among 27) when the integer number of citations is used becomes the second most highly ranked department.
► We also show that using these measures it is possible to test whether differences in the impact among units are statistically significant.