How can citation impact in bibliometrics be normalized? A new approach combining citing-side normalization and citation percentiles

• Published in: Quantitative science studies 2020-12, Vol.1 (4), p.1553-1569
• Main Author: Bornmann, Lutz
• Format: Article
• Language: English
• Subjects: Bibliometrics; citation analysis; citation percentiles; citing-side normalization; Mathematical analysis; Skewed distributions
• ISSN: 2641-3337; 2641-3337
• DOI: 10.1162/qss_a_00089

Since the 1980s, many different methods have been proposed to field-normalize citations. In this study, an approach is introduced that combines two previously introduced methods: citing-side normalization and citation percentiles. The advantage of combining two methods is that their advantages can be integrated in one solution. Based on citing-side normalization, each citation is field weighted and, therefore, contextualized in its field. The most important advantage of citing-side normalization is that it is not necessary to work with a specific field categorization scheme for the normalization procedure. The disadvantages of citing-side normalization—the calculation is complex and the numbers are elusive—can be compensated for by calculating percentiles based on weighted citations that result from citing-side normalization. On the one hand, percentiles are easy to understand: They are the percentage of papers published in the same year with a lower citation impact. On the other hand, weighted citation distributions are skewed distributions with outliers. Percentiles are well suited to assigning the position of a focal paper in such distributions of comparable papers. The new approach of calculating percentiles based on weighted citations is demonstrated in this study on the basis of a citation impact comparison between several countries.