Per Journal Demographics and Linear Regression Analysis of Authorship over Time.

Data collected per journal (Starting year in which data was collected on MEDLINE, total # of articles analyzed, total # of authors analyzed, mean number of authors/article for all years included per journal). Linear regression analysis of the relationship between mean number of authors/article per journal and time. See S1 Table for full journal names. Explicit endorsement of ICJME guidelines on each journal’s website was determined. 1) Explicitly endorses ICMJE. 2) Does not explicitly endorse ICMJE but has a statement regarding authorship criteria in their instructions for authors. 3) Has no mention of ICJME or authorship contributions.