A relative authorship index. A new metric for evaluating individual contribution in scientific research

This study presents the relative authorship index (RAI), a novel metric designed to address the limitations of traditional bibliometric indicators, such as publication counts, citation numbers, and the h-index, by correcting for authorship inflation. Conventional metrics can overestimate productivity by failing to account for the number of co-authors or the possibility of inflated authorship. To detect such inflation, this index evaluates the number of co-authors on a paper relative to the number of authors in the references cited within the same paper, which are assumed to reflect the researcher's specific field of study. By using this field-specific baseline, the index identifies whether a publication involves an unusually high number of co-authors compared to field standards, thus flagging potential authorship inflation. Applied to neuroscience articles authored by researchers affiliated with Italian universities, the index revealed significant regional and university differences, with higher values in southern regions and private universities. A case study of a single department also revealed high variability among individual researchers, indicating that the index can capture consistent patterns in authorship practices. In addition, we propose an authorship correction formula to adjust bibliometric indicators. The formula introduces parameters that penalize authorship inflation based on the RAI and also penalize large co-author counts, with the latter scaled according to whether the researcher occupies key authorship positions (first, last, and/or corresponding author).