A compact representation of authorship-position composition and its relevance to bibliometric indicators

Quantitative indicators such as citation counts and h-type indices are widely used in research evaluation, yet they primarily capture cumulative output and often overlook structural differences in how researchers participate in collaborative scientific work. Authorship order provides a scalable but imperfect indicator of how researchers are positioned within collaborative publication records, but its organization at the researcher level has not been systematically characterized. Here, we analyze authorship composition among highly cited researchers in the life sciences and medicine and examine whether authorship-position profiles can be summarized by a small number of dimensions. Principal component analysis identified two dominant axes. The first contrasted profiles concentrated in first and last authorship with those dominated by middle authorship, while the second distinguished first-author–weighted from last-author–weighted profiles. These axes showed broadly similar descriptive patterns across career cohorts and major scientific domains. The first/last-author concentration axis showed modest but detectable associations with several career-level bibliometric indicators, although the direction and magnitude of these associations varied by indicator. Sensitivity analyses suggested that the observed structure was partly influenced by the compositional constraint of authorship shares, but related patterns remained evident. Together, these findings suggest that authorship-position composition can provide descriptive context for interpreting bibliometric indicators among highly cited researchers, rather than serving as a measure of individual contribution or research value.