Table 1

Frequencies of author contributions, and of conditions for fulfilling author requirements, overall and by author rank on the byline, among 1139 authors of research articles published in 2015 in the Annals of Internal Medicine

Author contributionMedian no of contributing authors per article (range)Overall,
% (n)
According to author rank, %
FirstSecondMiddleNext to lastLastp Value*
1. Conception and design of the study4 (1–17)52.2 (595)95.361.536.649.687.4<0.001
2. Analysis and interpretation of the data6 (0–22)73.6 (838)97.789.963.463.089.9<0.001
3. Drafting of the article4 (1–13)45.7 (520)98.457.832.240.058.0<0.001
4. Critical revision of the article for important intellectual content6 (1–26)74.8 (852)83.779.869.369.696.6<0.001
5. Final approval of the article7 (2–29)88.8 (1011)96.985.386.188.798.3<0.001
6. Provision of study materials or patients1 (0–18)24.2 (276)36.416.523.817.426.90.002
7. Statistical expertise2 (0–6)22.8 (260)48.129.415.918.332.8<0.001
8. Obtaining of funding1 (0–11)17.6 (200)38.013.88.414.852.9<0.001
9. Administrative, technical or logistical support2 (0–15)28.5 (325)38.026.623.134.844.5<0.001
10. Collection and assembly of data4 (0–20)49.7 (566)76.055.045.439.150.4<0.001
  • *From logistic regression model with the author contribution as dependent variable, article as random factor and author rank as fixed factor.