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Key MEDLINE® Indicators

  FY2016 % Change FY2015 % Change FY2014 % Change FY2013 % Change
Citations Indexed for MEDLINE 869,666 +8% 806,326 +5% 765,850 +4% 734,052 -3.5%
MEDLINE/PubMed® Searches1 3.2 Billion +14% 2.8 Billion +4% 2.7 Billion +8% 2.5 Billion +14%
Sub-Total: Web3 853 Million -6% 910 Million +1% 900 Million -3% 932 Million 0%
Sub-Total: API3 2.8 Billion +21% 1.9 Billion +6% 1.8 Billion +13% 1.6 Billion +23%
Journal Titles in MEDLINE 5,6238 +0.1% 5,6188 -0.5% 5,6478 +0.1% 5,6408 +0.1%
Journal Titles in
Index Medicus6
5,1368 +0.3% 5,1238 +0.1% 5,1188 +1% 5,0678 +0.8%
Total Citation Data Creation9 1,020,678 +16% 879,709 -10% 981,783 +6% 926,479 +6%
OCRed Citations 39,051 -11% 43,864 -21% 55,222 -8% 60,019 -4%
Citations Received
Electronically via XML
981,627 +17% 835,845 -10% 926,561 +7% 866,460 +7%
Retraction Notices 64110 -4%10 66610 +41%10 4735, 10 +15%5, 10 410 +18%
Retracted Articles 66410 -3%10 68410 +37%10 5005, 10 +7%5, 10 467 +25%
Partial Retraction Notices7 ---- ---- 4 +400% 0 -300% 3 +200%
Partially Retracted Articles7 ---- ---- 4 +400% 0 -300% 3 +200%
Errata 8,992 -27% 12,344 +29% 9,602 +5% 9,178 +13%
Comments 47,906 -9% 52,921 -7% 56,652 +16% 48,714 +31%
Gene Indexing 86,458 +3% 83,734 +7% 78,491 -8% 85,429 -4%

 

See also additional MEDLINE statistics.

Prior Years:
2010-2012
2005-2009
2000-2004
1996-1999

The U.S. Government Fiscal Year (FY) runs from October 1 - September 30.

Not all footnotes apply to archived years.

Note:  See Errata Fact Sheet for definitions. NLM began to report retracted articles separately in FY2003. Prior to that the numbers reported were Retraction Notices only.

Note:  See Gene Indexing and Entrez Gene. Gene indexing began to be phased in during 4th Quarter FY2001 (Jul-Sep) with several hundred links. In 2005, gene indexing changed from LocusLink, where 10 organisms were in scope, to Entrez Gene, where more than 1,800 organisms are in scope. In 2007, gene indexing was applied to more clinical genetics articles.

1Statistical gathering method refined in FY2009.
2June 2007 implementation of Entrez 2.0 ("portals") resulted in changes to the statistical gathering process. FY2008 represents a new baseline for the data and cannot be compared to FY2007.
3Sub-Total labels changed for FY2012 from "Web/Interactive" to "Web" and from "Scripts/E-Utilities" to "API" (Application Programming Interface).
4FY2011 is last full reporting year for the original NLM Gateway; it was transitioned to a new pilot project containing two databases in December 2011. See Reminder: NLM Gateway Changing for additional information.
5Corrected from previously reported numbers:

  • FY2008 Gateway Searches previously 998 Million
  • FY2008 Total Citation Data Creation previously 726,097

  • FY2011 Retraction Notices previously 267 and +21%
  • FY2011 Retracted Articles previously 273

  • FY2014 Retraction Notices previously 373 and -9%
  • FY2014 Retracted Articles previously 400 and -14%

6 Index Medicus® was a monthly bibliographic listing of current biomedical references derived from MEDLINE. The item remains an online indicator in MEDLINE citations found in PubMed. Index Medicus® ceased in print after December 2004 edition.
7 NLM began to report partial retractions separately in December 2006; discontinued in September 2016. All past and future partial retractions are handled as errata.
8The small net increase or decrease results from identification of journals that have ceased publication or for which NLM is no longer receiving citation data electronically; it does not mean that fewer new journals were recommended for indexing.
9Includes PubMed citations that are in these subsets [sb]: inprocess [sb], MEDLINE [sb], OLDMEDLINE [sb], and PubMednotMEDLINE [sb] (completed out-of-scope). Does not include PubMed citations that are publisher [sb]; these are the ahead-of-print, author manuscripts, and Bookshelf-derived citations.
10For Retraction Notices, statistical gathering method changed to count the number of links made between Retraction Notices and Retracted Articles during the fiscal year for any citation in PubMed (not limited to MEDLINE journals); previously, NLM counted the number of Retraction Notice citations completed during the fiscal year. For Retracted Articles, the count has always been the number of citations referenced by the Retraction Notices, regardless of whether a citation for the original paper exists in PubMed.


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1996-1999

  FY1999 % Change FY1998 % Change FY199715 % Change FY199615
Citations Indexed for MEDLINE 434,000 +5% 411,921 -21% 519,012 +38% 322,825
MEDLINE/PubMed® Searches16 ---- --- --- --- --- --- ---
Journal Titles in MEDLINE 4,007 +2% 3,942 +2% 3,879 <+1% 3,868
Journal Titles in
Index Medicus7
3,378 +2% 3,302 +3% 3,211 <+1% 3,200
Total Citation Data Creation 453,000 +4% 434,000 -13% 496,000 +33% 336,000

Keyboarded Citations13

198,000 -24% 260,000 -41% 434,000 +23% 336,000

OCRed Citations8

151,000 +16% 130,000 +53% 62,000 --- 0

Citations Received
Electronically via XML9

104,000 +136% 44,000 --- 0 --- 0
Retraction Notices10 33 -38% 53 +112% 25 +56% 16
Retracted Articles10 ---- ---- ---- ---- ---- ---- ----
Errata10 2,848 -42% 4,953 +40% 3,526 +245% 1,021
Comments10 16,270 -4% 16,867 -46% 30,986 +48% 20,952

See also additional MEDLINE statisitics.

Current Years
Prior Years:
2005-2009
2000-2004
1996-1999

The U.S. Government Fiscal Year (FY) runs from October 1 - September 30.

Not all footnotes apply to archived years.

1Statistical gathering method changed effective with April 2003 data.
2Includes Internet Grateful Med® searches totaling about 27 million.
3NLM Gateway was released to the public on October 16, 2000 but the statistics include only April-September 2001 usage.
4The net increase of one journal resulted from the deselection of nearly 250 nursing and dental journals that had not been indexed for several years and the addition of about 50 titles from the former SPACELINE, HISTLINE®, and BIOETHICSLINE® databases. These journals were not included in IM.
5About 40 titles of the increase were due to the addition of former AIDSLINE® titles.
6Re: FY2000 - About half of the 325 title increase was due to the addition of former HealthSTAR titles. The remainder are new titles.
7Index Medicus® (ceased in print after December 2004 issue) was a monthly bibliographic listing of current biomedical references derived from MEDLINE. Included: subject and author sections and separate Bibliography of Medical Reviews. Remains an online indicator in MEDLINE citations found in PubMed.
8Optical Character Recognition after scanning.
9eXtensible Markup Language
10See Errata Fact Sheet for definitions. NLM began to report retracted articles separately in FY2003. Prior to that the numbers reported were Retraction Notices only.
11No maintenance was done on comments and errata from October 2000 - April 2001 as the new maintenance system was being developed and tested.
12Includes revised and re-edited comments entered in previous years.
13Keyboarding ceased as a method of data entry in June 2004.
14Numbers are coincidentally the same; there were 3 notices published twice (retracting the same publications) while there were some notices retracting multiple articles.
15There was a data entry and concomitant indexing backlog resulting from the General Services Administration Board of Contract Appeals' suspension of NLM editing and data entry contract from late February 1996 to late April 1996. The large backlog was eliminated in early April 1997. This caused fewer records to be added to MEDLINE during FY1996 and a greater number added in FY1997.
16For comparison, ELHILL® (mainframe computer retrieval software for MEDLINE and other NLM databases) searches were 7,397,000 in FY1996; 8,741,000 in FY1997; 15,600,000 in FY1998; and dropped to about 3,000,000 in FY1999 when ELHILL ceased Sept. 30, 1999 for direct searching. That drop is attributed to the main search access having shifted to PubMed (including IGM, Internet Grateful Med) which was estimated to be 220 million searches for FY1999.
17June 2007 implementation of Entrez 2.0 ("portals") resulted in changes to the statistical gathering process. FY2008 represents a new baseline for the data and cannot be compared to FY2007.
18Statistical gathering method was enhanced effective October 2006 to collect previously unreported access.
19Includes about 110 history of medicine journals and 13 bioethics journals.
20NLM began to report partial retractions separately in December 2006.


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