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Number of Authors per MEDLINE/PubMed Citation

Citations may contain personal author and/or collective (group or corporate) author names (see summary below). As illustrated by the following graph, the number of personal authors per citation has risen steadily since 1950. There is a small pattern of growth in the number of collective authors in recent years.

Graph of personal and corporate author number trends from 1950 to 2006

Statistics were produced at the conclusion of NLM's 2006 production year and generated from the MEDLINE/PubMed baseline files which consist of all completed records in PubMed. The baseline files exclude PubMed records identified as "in process" or "as supplied by publisher" (approx. 3% of the total). Note that very few citations from 1966-2000 contain collective author data (see #7, below).

The above data is extracted from author_counts.xls (Microsoft Excel file, 63 KB). This Excel workbook includes two spreadsheets with author data by year. Data include counts and averages of personal author names, collective author names, and combined, with the maximum instances of each for every year presented. This data is also available in author_counts_recent.pdf (6 KB) and author_counts.pdf (34 KB, Adobe Acrobat Reader required).

Personal Author Counts

Publication Dates Total Number Records Records with Personal Author Information Author Occurrences Average # Author Occurrence Maximum # Author Occurrence
All 16,120,074
 15,759,357
 49,792,823
 3.16 743
2005-2007 983,724
 971,139
 4,388,746
 4.52 651
2000-2004 2,710,155
 2,669,317
 11,074,664
 4.15 744
1995-1999 2,185,143
 2,141,614
 8,087,598
 3.78 230
1990-1994 1,979,427
 1,939,737 6,595,344
 3.40 30
1985-1989 1,746,091
 1,708,684
 5,358,455
 3.14 77
1980-1984 1,439,967
 1,407,886
 3,987,490
 2.83 50
1975-1979 1,289,566
 1,252,987
 3,125,528
 2.49 49
pre-1975 3,786,001
 3,684,549
 7,227,722
 1.96 26


CollectiveName (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 16,120,074
 48,969
 52,724
 1.08 25
2000-2007 983,724
 12,705
 14,124
 1.11 18
2000-2004 2,710,155 26,873
 29,058
 1.08 25
1995-1999 2,185,143 1,624
 1,653
 1.02 4
1990-1994 1,979,427 1,885
 1,905
 1.01 4
1985-1989 1,746,091 3,171
 3,225
 1.02 4
1980-1984 1,439,967 1,674
 1,719
 1.03 3
1975-1979 1,289,566 856 859 1.00 1
pre-1975 3,786,001 181
 276
 1.00 1

Summary:

Number of Citations: 16,120,074
Number of Citations with Personal Author: 15,759,357
Number of Citations with Collective Name: 48,969
Number of Citations with Personal Author and/or Collective Name: 15,775,913
Number of Citations with no Personal Author: 360,717
Number of Citations with no Collective Name: 16,071,105
Number of Citations with Personal Author(s), no Collective Name: 15,726,944
Number of Citations with Collective Name(s), no Personal Author: 16,556
Number of Personal Authors: 49,792,823
Largest Personal Authors Count (PMID 11289970): 743
Number of Collective Names: 52,724
Largest Collective Names Count (PMID 15617175): 25
Number of Personal Author and/or Collective Name: 49,845,547
Largest Combined Personal Author/Collective Name Count (PMID 11289970): 744

The data in the charts and summary above were extracted from the 2007 Statistical Reports on MEDLINE/PubMed Baseline Data, which include detailed statistics on number of occurrences and byte size of all data elements in the baseline database.

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

  1. Effective January 1984 (entry month) personal authors were limited to a maximum of 10.
  2. Effective with 1992 date of publication, letters are indexed individually with authors rather than as an anonymous group.
  3. Effective with 1996 date of publication, the personal author limit was raised to a maximum of 25.
  4. Effective with 2000 date of publication, the personal author limit was removed.
  5. Until 1990, NLM transliterated up to five authors' Cyrillic or Japanese names to the Roman alphabet.
  6. 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.
  7. 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's data creation partners. Citations from 1966-2000 with collective author field data are generally those created by NLM's data creation partners, and are very few in number and typically in the population or ethics subject areas.
  8. 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 names. 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 Technical Bulletin article for details.
  9. 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 more information about the MEDLINE author and corporate author fields.

Last updated: 06 February 2007
First published: 02 July 2002
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