Inflated Co-authorship Introduces Bias to Current Scientometric Indices

Background: Although scientometry gradually became prevalent way of measuring one's research output, there are many inherent drawbacks in main indices that are used: impact factor, number of citations, number of published papers and Hirsch's index. Objective: The aim of this study was to analyze effects of inflated co-authorship on values of scientometric indices among authors in biomedicine who participated in published papers with more than 30 co-authors. Methods: The study was of cross-sectional type, based on 100 publications randomly extracted from the MEDLINE database. The inclusion criterion was publication with more than 30 authors. The studies with topics not related to humans were excluded from further analysis. Results: On average about 10% of papers published by the surveyed authors had more than 30 co-authors, but these papers brought more than 40% of all citations and more than 40% of Hirsch's index attributed to these authors. The duration of scientific activity was well correlated to number of citations, Hirsch's index and the number of publications themselves with 30 or less co-authors, while the correlation did not exist with number of citations, Hirsch's index and the number of publications with more than 30 authors. In summary, publications with > 30 authors carry more scientometric points than publications with less co-authors, and the researchers with shorter scientific activity had larger scientometric benefit from publications with more than 30 authors than senior researchers. Conclusion: Unjustified and prolific co-authorship is one of methods for inflation of scientometric indices that are not further reflecting true quality of research output of an individual. Further improvement of scientometric indicators may prevent unjustified co-authorship if it reflects the work invested in a research result