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.

*The data presented on this Web page were extracted from the 2023 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 2022 production year, which occurred in January, after the global updating for the new year of MeSH (Medical Subject Headings). Note that very few citations from 1966-2000 contain collective author data (see #3, 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	34,960,700	34,218,945	150,368,250	4.39	5,154
2020-2023*	4,581,533	4,537,573	28,972,185	6.38	2,959
2015-2019	5,734,130	5,659,731	33,319,720	5.89	5,154
2010-2014	4,682,383	4,635,593	24,036,330	5.19	3,172
2005-2009	3,589,706	3,543,064	16,287,408	4.60	926
2000-2004	2,838,537	2,784,353	11,434,849	4.11	900
1995-1999	2,332,909	2,280,869	8,550,588	3.75	631
1990-1994	2,106,745	2,057,851	6,973,436	3.39	108
1985-1989	1,842,845	1,797,053	5,619,463	3.13	77
1980-1984	1,487,474	1,450,157	4,081,520	2.81	100
1975-1979	1,321,033	1,281,032	3,181,150	2.48	49
pre-1975	4,443,132	4,191,669	7,911,601	1.89	37

 

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	34,960,700	268,896	294,238	1.09	1,152
2020-2023*	4,581,533	36,730	40,463	1.10	1152
2015-2019	5,734,130	71,959	77,698	1.08	163
2010-2014	4,682,383	56,159	61,924	1.10	17
2005-2009	3,589,706	43,266	47,935	1.11	29
2000-2004	2,838,537	27,367	29,588	1.08	25
1995-1999	2,332,909	2,011	2,060	1.02	4
1990-1994	2,106,745	2,108	2,147	1.02	16
1985-1989	1,842,845	3,335	3,389	1.02	4
1980-1984	1,487,747	1,776	1,821	1.03	3
1975-1979	1,321,033	915	919	1.00	2
pre-1975	4,443,132	2,813	2,817	1.00	2

 

Summary

Summary of Personal Author and Collective Name Counts	Total
Number of Citations	34,960,700
Number of Citations with Personal Author	34,218,945
Number of Citations with Collective Name	268,896
Number of Citations with Personal Author and/or Collective Name	34,260,427
Number of Citations with no Personal Author	741,755
Number of Citations with no Collective Name	34,691,804
Number of Citations with Personal Author(s), no Collective Name	33,991,531
Number of Citations with Collective Name(s), no Personal Author	41,482
Number of Personal Authors Occurrences	150,368,250
Largest Personal Authors Count (PMID 27770180)	5,154
Number of Collective Names Occurrences	294,238
Largest Collective Names Count (PMID 30236235)	1,152
Number of Personal Author and/or Collective Name Occurrences	150,662,488
Largest Combined Personal Author/Collective Name Count (PMID 27770180)	5,156
Number of Citations with Author Identifiers	3,016,878
ORCID	3,016,878
Number of Personal Authors Occurrences with Author Identifiers	6,846,668
ORCID	6,846,710
Number of Citations with Investigator Identifiers	34

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 Authorship in MEDLINE. See also more information about the MEDLINE author, corporate author, investigator, and author identifier fields.

Last Reviewed: May 27, 2023