Table 1.
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.
Fig 1.
Overall mean number of authors/article for all included journals from 1946 to 2013.
Analysis of mean authorship trends over time for radiology journals from 1946 to 2013. Time points for the implementation and major revisions to ICJME guidelines in 1979, 1997, 2003, 2010 and 2013 are denoted by red arrows.
Fig 2.
Mean Number of Authors/Article and Change of Authorship per Journal.
This is a double axis bar chart showing the mean number of authors/article per journal and the overall change in authorship per journal over time. Journals were organized by change in authorship over time. All journals show an increase in the change in authorship over time with the exception of the Korean Journal of Radiology which has a -0.003 change of authorship per year.
Fig 3.
Average Number of Authors/Article per Year for Top 10 Contributing Journals.
This graph shows the mean number of authors/article for the Top 10 contributing journals by # of articles published relative to the # of articles published for all radiology journals analyzed.
Fig 4.
Mean Number of Authors/Article and Change of Authorship per Country.
This is a double axis bar chart showing the mean number of authors/article per journal and the overall change in authorship per country over time. Countries were organized by change in authorship over time. Most countries analyzed show an increase in authorship over time with the exception of Tunisia (-0.029), Peru (-0.026), Croatia (-0.008), Belgium (-0.006) and Egypt (-0.003).
Fig 5.
Mean Number of Authors/Article from 1946–2013 by Publication Type.
This graph shows the mean number of authors/article for the three publication types analyzed: 1) Case Reports, 2) Reviews and 3) Original Research.
Fig 6.
Average Authorship from 1946–2013 by Publication Language.
* Trendline for Italian language journals was not included due to data being available for only 2 publication years.
Table 2.
Per Publication Language Linear Regression Analysis of Change of Authorship over Time.
Fig 7.
Relationship between Impact Factor and Average Authorship in 2013.
The 2013 impact factor of journals analyzed compared against the average number of authors/article in 2013. JBR-TBR and Journal of Radiology Case Reports were excluded from this graph as they did not have a 2013 impact factor.