Research coauthorship 1900-2020: Continuous, universal, and ongoing expansion

Research coauthorship is useful to combine different skill sets, especially for applied problems. While it has increased over the last century, it is unclear whether this increase is universal across academic fields and which fields coauthor the most and least. In response, we assess changes in the rate of journal article coauthorship 1900-2020 for all 27 Scopus broad fields and all 332 Scopus narrow fields. Although all broad fields have experienced reasonably continuous growth in coauthorship, in 2020, there were substantial disciplinary differences, from Arts and Humanities (1.3 authors) to Immunology and Microbiology (6 authors). All 332 Scopus narrow fields also experienced an increase in the average number of authors. Immunology and Classics are extreme Scopus narrow fields, as exemplified by 9.6 authors per Journal for ImmunoTherapy of Cancer article, whereas 93% of Trends in Classics articles were solo in 2020. The reason for this large difference seems to be the need for multiple complementary methods in Immunology, making it fundamentally a team science. Finally, the reasonably steady and universal increases in academic coauthorship over 121 years show no sign of slowing, suggesting that ever-expanding teams are a central part of current professional science.