Universality of citation distributions–A validation of Radicchi et al.'s relative indicator cf = c/c0 at the micro level using data from chemistry.

In a recently published PNAS paper, Radicchi, Fortunato, and Castellano (2008) propose the relative indicator c_f as an unbiased indicator for citation performance across disciplines (fields, subject areas). To calculate c_f, the citation rate for a single paper is divided by the average number of citations for all papers in the discipline in which the single paper has been categorized. c_f values are said to lead to a universality of discipline-specific citation distributions. Using a comprehensive dataset of an evaluation study on Angewandte Chemie International Edition (AC-IE), we tested the advantage of using this indicator in practical application at the micro level, as compared with (1) simple citation rates, and (2) z-scores, which have been used in psychological testing for many years for normalization of test scores. To calculate z-scores, the mean number of citations of the papers within a discipline is subtracted from the citation rate of a single paper, and the difference is then divided by the citations' standard deviation for a discipline. Our results indicate that z-scores are better suited than c_f values to produce universality of discipline-specific citation distributions. [ABSTRACT FROM AUTHOR]