title: Authorship in Radiation Oncology: Proliferation Trends Over 30 Years.
abstract: OBJECTIVE
  To investigate authorship trends in the radiation oncology literature.
  
  
  METHODS
  We examined the authorship credits of "original research articles" within 2 popular radiation oncology journals-International Journal of Radiation Oncology, Biology, Physics and Radiotherapy and Oncology-in 1984, 1994, 2004, and 2014. We compared the number of authors per publication during these 4 time periods using simple linear regression as a test for trend. We investigated additional author characteristics in a subset of articles.
  
  
  RESULTS
  A total of 2005 articles were eligible. The mean number of authors per publication rose from 4.3 in 1984 to 9.1 in 2014 (P<.001). On subset analysis of 400 articles, there was an increase in the percentage of multidisciplinary bylines (from 52% to 72%), multi-institutional bylines (from 20% to 53%), and publications with a trainee first author (from 16% to 56%) during the study period.
  
  
  CONCLUSIONS
  The mean number of authors per publication has more than doubled over the last 30 years in the radiation oncology literature. Possible explanations include increasingly complex and collaborative research as well as honorary authorship. Explicit documentation of author contributions could help ensure that scientific work is credited according to accepted standards.
authors.affiliation: Department of Radiation Oncology, University of Pennsylvania, Philadelphia, Pennsylvania. Electronic address: eric.ojerholm@uphs.upenn.edu.
authors.forename: Eric
authors.initials: E
authors.lastname: Ojerholm
authors.affiliation: Department of Radiation Oncology, University of Pennsylvania, Philadelphia, Pennsylvania.
authors.forename: Samuel
authors.initials: S
authors.lastname: Swisher-McClure
mesh_terms: D001319:Authorship; D015706:Bibliometrics; D003299:Cooperative Behavior; D035081:Editorial Policies; D006801:Humans; D033183:Interdisciplinary Communication; D010506:Periodicals as Topic / Q000706:statistics & numerical data*; D018787:Radiation Oncology / Q000706:statistics & numerical data / Q000639:trends*; D013997:Time Factors