Analysis of justification for author order and gender bias in author order among those contributing equally

The practice of designating two or more authors as equal contributors (ECs) on a scientific publication is increasingly common as a form of sharing credit. However, EC authors are often unclearly attributed on curriculum vitae (CVs) or citation engines, and it is unclear how research teams determine author order within an EC listing. In response to studies showing that male authors were more likely to be placed first in an EC listing, the American Society for Microbiology (ASM) required that authors explain the reasons for author order beginning in 2020. In this study, we analyze data from over 2,500 ASM publications to see how this policy affected gender bias and how research teams are making decisions on author order. Data on publications from 2018 to 2021 show that gender bias was largely nonsignificant both before and after authors were asked by ASM to provide an EC statement. The most likely reasons for EC order included alphabetical order, seniority, and chance, although there were differences for publications from different geographic regions. However, many research teams used unique methods in order selection, highlighting the importance of EC statements to provide clarity for readers, funding agencies, and tenure committees.IMPORTANCE First-author publications are important for early career scientists to secure funding and educational opportunities. However, an analysis published in eLife in 2019 noted that female authors are more likely to be placed second even when both authors report they have contributed equally. American Society for Microbiology announced in response that they would require submissions to include a written justification of author order. In this paper, we analyze the resultant data and show that laboratories are most likely to use some combination of alphabetical order, seniority, and chance to determine author order. However, the prevalence of these methods varies based on the research team's geographic location. These findings highlight the importance of equal contributor statements to provide clarity for readers, funding agencies, and tenure committees. Furthermore, this work is critically important for understanding how these decisions are made and provides a glimpse of the sociology of science. First-author publications are important for early career scientists to secure funding and educational opportunities. However, an analysis published in eLife in 2019 noted that female authors are more likely to be placed second even when both authors report they have contributed equally. American Society for Microbiology announced in response that they would require submissions to include a written justification of author order. In this paper, we analyze the resultant data and show that laboratories are most likely to use some combination of alphabetical order, seniority, and chance to determine author order. However, the prevalence of these methods varies based on the research team's geographic location. These findings highlight the importance of equal contributor statements to provide clarity for readers, funding agencies, and tenure committees. Furthermore, this work is critically important for understanding how these decisions are made and provides a glimpse of the sociology of science.