Gender homophily: In-group citation preferences and the gender disadvantage

Based on an extensive sample of articles in the life sciences, we find that gender homophily in forward citations is substantial: compared to men-led articles (i.e., those with men as either the first or last author), women-led articles receive fewer forward citations from subsequent men-led articles and more forward citations from subsequent women-led articles. This occurs across life science fields with varying gender ratios. Forward citations flow differentially to papers led by women versus men for a variety of reasons, including the detailed field and scientific concepts covered in the articles, the journals in which they are published, article length, authors' research experience, and the size of the author team. After accounting for this extensive set of factors, we find some forward citations appear to be driven by gender citation homophily – that is, gender alignment between citing and cited authors. This pattern greatly disadvantages women in fields where they are underrepresented, leading to a gender citation gap, compared to more gender-balanced fields, where the gap is shrinking. We also find that articles written by more recent cohorts of scientists are subject to less gender citation homophily than earlier cohorts. Investigation into potential pathways by which gender citation homophily operates suggests it stems from gendered specialization in research niches and, to a lesser extent, from gender homophily in professional connections among scientists, as opposed to from direct discrimination against unknown authors based on gender inferred from their names. Since gender homophily in citations impedes gender-indifferent knowledge flow in most fields, its adverse impact on science likely includes not only slowing women's careers but also creating a less efficient diffusion of knowledge and recombination of work from earlier papers into newer work.