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Number of Authors per MEDLINE®/PubMed® Citation

Citations may contain personal author and/or collective (group or corporate) author names*. As illustrated by the following graph, the number of personal authors per citation has risen steadily since 1950.

Graph of personal and corporate author number trends from 1950 to 2013

*The data presented on this Web page were extracted from the 2014 Statistical Reports on MEDLINE®/PubMed® Baseline Data (choose the Baseline Including OLDMEDLINE Records Excel option), which include detailed statistics on all data elements in the baseline database. The baseline contains all completed records in PubMed at the end of the NLM 2013 production year, which occurred in mid-November, after the global updating for the new year of MeSH (Medical Subject Headings). Publication Year 2013 is not yet complete and a few hundred citations with Publication Year 2014 are included. The baseline files exclude PubMed records identified as "in process" or "as supplied by publisher" (approx. 4% of the total). Note that very few citations from 1966-2000 contain collective author data (see #8, below).

Personal Author Counts

Publication Dates Total Number Records Records with Personal Author Information Author Occurrences Average # Author Occurrence Maximum # Author Occurrence
All   22,376,811 21,870,677 77,676,557 3.55 3,172
2010-2013* 2,930,909 2,903,675 14,862,477 5.12 3,172
2005-2009   3,539,158 3,496,205 16,110,814 4.61 656
2000-2004   2,774,842 2,726,010 11,242,692 4.12 743
1995-1999   2,243,943 2,195,327 8,261,776 3.76 631
1990-1994   2,029,741 1,984,178 6,723,488 3.39 97
1985-1989   1,787,178 1,743,874 5,447,578 3.12 77
1980-1984   1,474,934 1,437,699 4,053,072 2.82 100
1975-1979   1,312,841 1,273,297 3,165,174 2.49 49
pre-1975   4,283,167 4,110,315 7,809,145 1.90 38

Collective Name (Group or Corporate Author) Counts

Publication Dates Total Number Records Records with Collective Name Information Collective Name Occurrences Average # Collective Name Occurrence Maximum # Collective Name Occurrence
All   22,376,811 116,617 127,396 1.09 29
2010-2013* 2,930,909 36,151 39,839 1.10 17
2005-2009   3,539,158 43,096 47,773 1.11 29
2000-2004   2,774,842 27,260 29,484 1.08 25
1995-1999   2,243,943 1,845 1,890 1.02 4
1990-1994   2,029,741 1,967
1.02 16
1985-1989   1,787,178 3,197 3,251 1.02 4
1980-1984   1,474,934 1,697 1,742 1.03 3
1975-1979   1,312,841 876 879 1.00 2
pre-1975   4,283,167 527 530 1.01 2


Summary of Personal Author and Collective Name Counts Total
Number of Citations: 22,376,811
Number of Citations with Personal Author: 21,870,677
Number of Citations with Collective Name: 116,617
Number of Citations with Personal Author and/or Collective Name: 21,896,177
Number of Citations with no Personal Author: 506,134
Number of Citations with no Collective Name: 22,260,194
Number of Citations with Personal Author(s), no Collective Name: 21,779,560
Number of Citations with Collective Name(s), no Personal Author: 25,500
Number of Personal Authors: 77,676,557
Largest Personal Authors Count (PMID 21230962): 3,172
Number of Collective Names: 127,396
Largest Collective Names Count (PMID 19126777): 29
Number of Personal Author and/or Collective Name: 77,803,953
Largest Combined Personal Author/Collective Name Count (PMID 21230962): 3,173

Please note that the policy related to author names in MEDLINE has changed over time:

  1. For citations created from 1966-1983 October, NLM included all authors.
  2. For citations created from October 29, 1983, personal authors were limited to a maximum of 10.
  3. Effective with 1992 date of publication, letters are indexed individually with authors rather than as an anonymous group.
  4. Effective with 1996 date of publication, the personal author limit was raised to a maximum of 25 (i.e., the first 24 and the last author; author #25 up to the last author were omitted).
  5. Effective with 2000 date of publication, the personal author limit was removed.
  6. Until 1990, NLM transliterated up to five authors' Cyrillic or Japanese names to the Roman alphabet.
  7. Since 1990, the first ten Cyrillic or Japanese names are transliterated. Chinese ideograms are not transliterated by NLM, but if transliterations of the authors' names are available in the journal article or table of contents, they are included in the citation, even if that includes only one author in a multi-author article.
  8. Until 2001, collective (group or corporate) author information was added to the end of the article title where it remains for those retrospective records. As encountered, these records may be maintained to move the collective name to the collective author field. Note: Citations prior to 1966, in general, have no indication of collective author unless they were created by NLM data creation partners. Citations from 1966-2000 with collective author field data are generally those created by NLM data creation partners, and are very few in number and typically in the population or ethics subject areas.
  9. From 2001 to April 2006, the collective (group or corporate) name was the last occurrence in the author field, as a separate data element after any personal authors. Effective May 2006, the collective author is retained in the order of all authors found in the byline of the published article. See the May-June 2006 NLM Technical Bulletin article for details.
  10. Effective with 2002 date of publication, full personal author names (including full first and middle names) are routinely included in the records. Some NLM data creation partners entered full personal author names prior to this date as well.
  11. Beginning in mid-2005, the various policy restictions on number of authors entered in past years were lifted so that, on an individual basis, a record may be edited to include all author names present in the published article, regardless of the limitations in effect at the time the record was first created.
  12. Effective in late March 2008 for 2008 date of publication, NLM introduced the individual names associated with group authors. These study collaborators (investigators) had a role in the research but were not necessarily authors. See the March-April 2008 NLM Technical Bulletin article for details.
  13. Effective for 2013 date of publication, NLM cites author replies to comments separately.

Current practices and policies on how authorship is reflected in MEDLINE are described in the Fact Sheet: Authorship in MEDLINE. See also more information about the MEDLINE author and corporate author fields.