<p>Supplementary table 1. Prevalence of authorship policies in 5 highest impact-factor journals in selected categories indexed in 2009 edition of Science Citation Index or Social Sciences Citation Index and in a random third of all journals from selected categories of Arts & Humanities Citation index* Science Citation Index (SCI) No. of journals with authorship Journal category (total No. journals in the policy (out of 5 Source of authorship policy category) top ranked journals) Acoustics (28) 2 publisher (Elsevier) (n=2) own definition (n=2) Agriculture, multidisciplinary (35) 5 professional organization (ACS) (n=1) publisher (Elsevier) (n=2) publisher (Elsevier) (n=1) Agronomy (49) 2 publisher (Wiley-Blackwell) (n=1) Astronomy & Astrophysics (48) 0 own definition (n=1) Behavioural Sciences (45) 3 publisher (Elsevier) (n=2) Biochemistry & Molecular Biology (263) 3 own definition (n=3) own definition (n=1) Biology (79) 2 professional organization (COPE) (n=1) own definition (n=2) Chemistry, multidisciplinary (127) 5 professional organization (ACS) (n=3) own definition (n=1) Computer Science, interdisciplinary 3 publisher (Elsevier) (n=1) applications (92) professional organization (ICMJE) (n=1) own definition (n=1) Education, Scientific Disciplines (23) 4 publisher (Elsevier) (n=1) professional organization (ICMJE) (n=2) publisher (Elsevier) (n=1) Engineering, multidisciplinary (67) 2 publisher (Wiley-Blackwell) (n=1) own definition (n=2) Geosciences, multidisciplinary (137) 4 publisher (Elsevier) (n=2) History & Philosophy of Science (37) 0 own definition (n=2) Materials Science, multidisciplinary (189) 5 professional organization (ACS) (n=1) publisher (Elsevier) (n=2) Medicine, General & Internal (100) 4 professional organization (ICMJE) (n=4) Multidisciplinary Science (50) 4 own definition (n=4) own definition (n=2) Neurosciences (211) 3 publisher (Elsevier) (n=1) Physics, Multidisciplinary (69) 3 own definition (n=3) Statistics & Probability (91) 0 Telecommunications (66) 0 Veterinary Sciences (133) 2 publisher (Elsevier) (n=2) own definition (n=1) Zoology (124) 2 publisher (Elsevier) (n=1) Social Sciences Citation Index No. of journals with authorship Journal category (total No. journals in the policy (out of 5 Source of authorship definition category) top ranked journals) publisher (Elsevier) (n=1) Anthropology (58) 3 publisher (Wiley-Blackwell) (n=2) Business (72) 0 Economics (191) 1 publisher (Elsevier) (n=1) Education & Education Research (105) 0 Geography (44) 1 publisher (Elsevier) (n=1) History (17) 0 own definition (n=1) Information Science & Library Science (56) 2 professional organization (ICMJE) (n=1) Law (100) 0 Linguistics (55) 2 publisher (Elsevier) (n=2) own definition (n=1) Management (81) 3 publisher (Wiley-Blackwell) (n=2) Political Sciences (93) 0 Psychology, multidisciplinary (102) 4 professional organization (APA) (n=4) Social Sciences, interdisciplinary (57) 2 publisher (Elsevier) (n=2) own definition (n=1) Sociology (96) 2 publisher (Wiley-Blackwell) (n=1) Transportation (16) 4 publisher (Elsevier) (n=4) Arts and Humanities Citation Index No. of journals Category (No of analyzed journal/total No. with authorship Source of authorship definition in category) policy own definition (n=1) Archaeology (n=24/72) 3 publisher (Elsevier) (n=1) (no information available for 2 journals)† publisher (Wiley-Blackwell) (n=1) Architecture (n=12/36) publisher (Wiley-Blackwell) (n=1) 1 (no information available for 4 journals) Art (n=23/70) publisher (Wiley-Blackwell) (n=3) 3 no information (n=4) Humanities, multidisciplinary (n=35/111) own definition (n=1) 1 (no information available for 6 journals)‡ Literature (n=39/117) 0 (no information available for 5 journals) Music (n=25/76) own definition (n=1) 1 (no information available for 2 journals) Philosophy (n=47/141) publisher (Wiley-Blackwell) (n=4) 4 (no information available for 2 journals) Poetry (n=17/17) 1 publisher (Wiley-Blackwell) (n=1) Religion (n=42/118) own definition (n=1) 2 (no information available for 4 journals) publisher (Wiley-Blackwell) (n=1) Theatre (n=28/28) 0 (no information available for 3 journals) *The first 5 journals with the highest impact factor in each category of SCI and SSCI from the 2008 edition Journal Citation Records; journals’ web pages were available for all 5 first ranked journals. For A&HCI, a random 1 third of journals from 10 out of 27 subject categories indexed in the database, except for Poetry and Theatre, where all indexed journals were analyzed because of their small number. †The web page of the journal was not available and could not be found after extensive search of the Internet, or the web-page was not in function. ‡Publicaton of 1journal was discontinued.</p>