As publication-based metrics form the foundation of most university ranking systems, the growing prevalence of hyperauthored papers has emerged as an influential factor shaping ranking outcomes. Hyperauthored papers are defined here as those within the uppermost 0.1% of the cumulative author count distribution in each discipline. This study investigates universities in clinical medicine and physics included in the 2022 NTU Ranking to evaluate how hyperauthorship affects the measurement of research productivity. Four counting methods, namely whole counting, first author counting, fractional counting, and harmonic counting, are compared to assess changes in university rankings after excluding hyperauthored papers. The results demonstrate that hyperauthorship can substantially alter university rankings, with effects varying across disciplines, ranking tiers, and countries. In clinical medicine, the first-author counting method shows more pronounced effects on lower-ranked universities, while in physics whole counting also has stronger effects on lower-ranked universities. By comparison, rankings across all tiers remain relatively stable under fractional and harmonic counting methods, indicating that these methods are less influenced by hyperauthored papers. At the national level, universities in the United States and China generally rose in ranking following the exclusion of hyperauthored papers, while those in Germany and Italy declined, and institutions in the United Kingdom were largely unaffected. Whole counting exhibited the highest sensitivity to hyperauthorship, while fractional counting and harmonic counting proved the most robust. These findings highlight the importance of accounting for hyperauthorship in research evaluation frameworks and adopting counting practices that mitigate distortions in institutional performance assessment.

Liu Xiaojuan, Hu Wei, Huang Mu-hsuan, Liu Ting-Wei. The impact of hyperauthorship on university rankings across different counting methods [J]. Journal of Informetrics, 2026,20(4).