The evolution of order of authorship based on researchers' age

We examine the evolution of order of authorship based on seniority during 1975-2021. Results show that for small teams (<= 5 authors), the likelihood of placing the most junior author first has been increasing since the nineties. Additionally, the likelihood of placing the most senior author in last place has also been increasing. The results are at least partially driven by digitization of bibliographic records that drastically facilitated assignment of citations to all authors. We interpret our findings as a growing trend of small author teams becoming fairer. We do not find any significant effects for larger teams suggesting different practices when team size increases. Given that team size is, slowly but steadily, increasing over the last decades, the debate over the ethical considerations around authorship practices should place significance on the number of co-authors.