Skip Navigation Bar

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 2015

*The data presented on this Web page were extracted from the 2016 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 2015 production year, which occurred in mid-November, after the global updating for the new year of MeSH (Medical Subject Headings). Publication Year 2015 is not yet complete and fewer than three dozen citations with Publication Year 2016 are included in the All category. 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 Personal Author Occurrences Average # Personal Author Occurrence Maximum # Personal Author Occurrence
All   24,358,442 23,831,304 87,978,436 3.69 5,154
2015* 357,990 352,172 1,930,940 5.48 5,154
2010-2014 4,497,946 4,457,513 23,085,358 5.18 3,172
2005-2009   3,552,177 3,508,974 16,162,815 4.61 656
2000-2004   2,779,444 2,730,385 11,257,093 4.12 743
1995-1999   2,248,418 2,199,542 8,274,055 3.76 631
1990-1994   2,034,696 1,988,942 6,736,138 3.39 97
1985-1989   1,792,263 1,748,833 5,460,486 3.12 77
1980-1984   1,481,167 1,443,797 4,067,336 2.82 100
1975-1979   1,315,817 1,276,202 3,171,095 2.48 49
pre-1975   4,298,524 4,124,944 7,833,120 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   24,358,442 140,600 153,863 1.09 29
2015* 357,990 5,243 5,732 1.09 14
2010-2014 4,497,946 54,757 60,429 1.10 17
2005-2009   3,552,177 43,172 47,858 1.11 29
2000-2004   2,779,444 27,292 29,517 1.08 25
1995-1999   2,248,418 1,858 1,904 1.02 4
1990-1994   2,034,696 1,972
1.02 16
1985-1989   1,792,263 3,199 3,253 1.02 4
1980-1984   1,481,167 1,697 1,742 1.03 3
1975-1979   1,315,524 883 886 1.00 2
pre-1975   4,298,524 527 530 1.01 2



Summary of Personal Author and Collective Name Counts Total
Number of Citations: 24,358,442
Number of Citations with Personal Author: 23,831,304
Number of Citations with Collective Name: 140,600
Number of Citations with Personal Author and/or Collective Name: 23,859,446
Number of Citations with no Personal Author: 527,138
Number of Citations with no Collective Name: 24,217,842
Number of Citations with Personal Author(s), no Collective Name: 23,718,846
Number of Citations with Collective Name(s), no Personal Author: 28,142
Number of Personal Authors: 87,978,436
Largest Personal Authors Count (PMID 26024162): 5,154
Number of Collective Names: 153,863
Largest Collective Names Count (PMID 19126777): 29
Number of Personal Author and/or Collective Name: 88,132,299
Largest Combined Personal Author/Collective Name Count (PMID 26024162): 5,156
Number of Citations with Author Identifiers: 16,027
    ORCID: 16,027
Number of Personal Authors with Author Identifiers: 29,901
    ORCID: 29,901

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

  1. Number of personal authors:
    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 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).
    4. Effective with 2000 date of publication, the personal author limit was removed.
    5. Beginning in mid-2005, the various policy restrictions 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.
  2. Format of personal author names:
    1. Until about 2002 date of publication, author forenames (first and middle names) are initials only. See the January-February 2001 and November-December 2001 NLM Technical Bulletin articles.
    2. 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. See the May-June 2005 NLM Technical Bulletin article.
  3. Collective Names (also known as corporate names or group names):
    1. Until the 2001 indexing year (that started in mid-November 2000), 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.
    2. 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. See the March-April 2003 NLM Technical Bulletin article.
    3. 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.
  4. Collaborators (also known as investigators):
    1. 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.
  5. Identifiers for authors (both personal and collective) and for collaborators:
    1. Effective for 2010, NLM defined an element to contain a unique identifier associated with a name. This Identifier element began to be used by XML citation suppliers in 2013, largely for personal authors.
  6. Transliterations of author names:
    1. Until 1990, NLM transliterated up to five authors' Cyrillic or Japanese names to the Roman alphabet.
    2. Since 1990 to 2015, 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.
    3. As of 2016, author names are published in Roman characters in all MEDLINE journals, and NLM is no longer required to transliterate Cyrillic or Japanese names. All author names are included as published.
  7. Letters and author replies:
    1. Effective with 1992 date of publication, letters are indexed individually with authors rather than as an anonymous group.
    2. Effective for 2013 date of publication, NLM cites author replies to comments separately. See the September-October 2012 NLM Technical Bulletin article.
  8. Interviews:
    1. Effective for the 2015 indexing year, the interviewee becomes the first author and the interviewer is the second author on citations with Interview as the Publication Type [pt]. Previously only the interviewee was cited as the author.
    2. Effective 2016, authorship of interviews reflects the published record – an author is included if published in the article byline. Interviewees are not added as authors.

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, corporate author, investigator, and author identifier fields.