Paid Family and Childbearing Leave Policies at Top US Medical Schools

Of the 32 829 research articles published from 2005 through 2014 among 10 journals with high impact factors, 3706 (11.3%) credited multiple authors as equal contributors. After inspecting the bylines of these articles, 2250 (6.9%) had exactly 2 co-first authors. We excluded 1260 with co-first authors of the same gender and 128 with at least 1 co-first author of uncertain gender, leaving 862 eligible articles with co-first authors of different genders.