Impact factor: Wikis

  
  

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.The impact factor, often abbreviated IF, is a measure reflecting the average number of citations to articles published in science and social science journals.^ The recursive impact factors are normalized so that the average citations has a weight of 1.
  • IDEAS/RePEc Recursive Impact Factors for Series and Journals 22 January 2010 12:56 UTC ideas.repec.org [Source type: Academic]
  • IDEAS/RePEc Recursive Discounted Impact Factors for Journals 22 January 2010 12:56 UTC ideas.repec.org [Source type: Academic]

^ Journal impact factor: a brief review .
  • Journal impact factor: a brief review -- Garfield 161 (8): 979 -- Canadian Medical Association Journal 22 January 2010 12:56 UTC www.cmaj.ca [Source type: Academic]

^ It tracks the citations in selected journals and calculates the impact factor, which are published in the Journal Citation Report [18] .
  • First CytoJournal Peer-Reviewer's Retreat in 2006 - Open access, peer-review, and impact factor Shidham VB, Sandweiss L, Atkinson BF - CytoJournal 22 January 2010 12:56 UTC www.cytojournal.com [Source type: Academic]

.It is frequently used as a proxy for the relative importance of a journal within its field, with journals with higher impact factors deemed to be more important than those with lower ones.^ Journal impact factor: a brief review .
  • Journal impact factor: a brief review -- Garfield 161 (8): 979 -- Canadian Medical Association Journal 22 January 2010 12:56 UTC www.cmaj.ca [Source type: Academic]

^ It is one thing to use impact factors to compare journals and quite another to use them to compare authors.
  • Journal impact factor: a brief review -- Garfield 161 (8): 979 -- Canadian Medical Association Journal 22 January 2010 12:56 UTC www.cmaj.ca [Source type: Academic]

^ It is, however, still important to use the JCR impact factor carefully.
  • Comparison of Journal Citation Reports and Scopus Impact Factors for Ecology and Environmental Sciences Journals 22 January 2010 12:56 UTC www.istl.org [Source type: Academic]

.The impact factor was devised by Eugene Garfield, the founder of the Institute for Scientific Information (ISI), now part of Thomson Reuters.^ The impact factor is calculated each year by a commercial company- Thomson Scientific, also known as the Institute for Scientific Information (ISI) [17] .
  • First CytoJournal Peer-Reviewer's Retreat in 2006 - Open access, peer-review, and impact factor Shidham VB, Sandweiss L, Atkinson BF - CytoJournal 22 January 2010 12:56 UTC www.cytojournal.com [Source type: Academic]

^ Impact factor Thompson Scientific 2004.
  • First CytoJournal Peer-Reviewer's Retreat in 2006 - Open access, peer-review, and impact factor Shidham VB, Sandweiss L, Atkinson BF - CytoJournal 22 January 2010 12:56 UTC www.cytojournal.com [Source type: Academic]

^ The Thomson Scientific impact factor.
  • Comparison of Journal Citation Reports and Scopus Impact Factors for Ecology and Environmental Sciences Journals 22 January 2010 12:56 UTC www.istl.org [Source type: Academic]

.Impact factors are calculated yearly for those journals that are indexed in Thomson Reuter's Journal Citation Reports.^ Journal impact factor: a brief review .
  • Journal impact factor: a brief review -- Garfield 161 (8): 979 -- Canadian Medical Association Journal 22 January 2010 12:56 UTC www.cmaj.ca [Source type: Academic]

^ The equation for calculation of the impact factor.
  • Understanding the Limitations of the Journal Impact Factor -- Kurmis 85 (12): 2449 -- Journal of Bone and Joint Surgery 22 January 2010 12:56 UTC www.ejbjs.org [Source type: Academic]

^ It tracks the citations in selected journals and calculates the impact factor, which are published in the Journal Citation Report [18] .
  • First CytoJournal Peer-Reviewer's Retreat in 2006 - Open access, peer-review, and impact factor Shidham VB, Sandweiss L, Atkinson BF - CytoJournal 22 January 2010 12:56 UTC www.cytojournal.com [Source type: Academic]

Contents

Calculation

.In a given year, the impact factor of a journal is the average number of citations to those papers that were published during the two preceding years.^ The recursive impact factors are normalized so that the average citations has a weight of 1.
  • IDEAS/RePEc Recursive Impact Factors for Series and Journals 22 January 2010 12:56 UTC ideas.repec.org [Source type: Academic]
  • IDEAS/RePEc Recursive Discounted Impact Factors for Journals 22 January 2010 12:56 UTC ideas.repec.org [Source type: Academic]

^ It tracks the citations in selected journals and calculates the impact factor, which are published in the Journal Citation Report [18] .
  • First CytoJournal Peer-Reviewer's Retreat in 2006 - Open access, peer-review, and impact factor Shidham VB, Sandweiss L, Atkinson BF - CytoJournal 22 January 2010 12:56 UTC www.cytojournal.com [Source type: Academic]

^ Do journals published by BioMed Central have Impact Factors and are their citations tracked?
  • BioMed Central | about us | General FAQ 22 January 2010 12:56 UTC www.biomedcentral.com [Source type: Academic]

[1] For example, the 2008 impact factor of a journal would be calculated as follows:
A = the number of times articles published in 2006 and 2007 were cited by indexed journals during 2008
.B = the total number of "citable items" published in 2006 and 2007. ("Citable items" are usually articles, reviews, proceedings, or notes; not editorials or Letters-to-the-Editor.^ The impact factor of a journal is calculated by dividing the references cited in one year by the number of citable articles published in the same journal over the previous two years.
  • Comparison of Journal Citation Reports and Scopus Impact Factors for Ecology and Environmental Sciences Journals 22 January 2010 12:56 UTC www.istl.org [Source type: Academic]

^ Generally, the number of citable articles in JCR corresponds to the number of research and review articles indexed in Web of Science for any particular journal, however, the two numbers don't always correspond.
  • Comparison of Journal Citation Reports and Scopus Impact Factors for Ecology and Environmental Sciences Journals 22 January 2010 12:56 UTC www.istl.org [Source type: Academic]

^ Because we relied on the number of citable articles from JCR to create our Scopus impact factor, any title that isn't completely indexed by Scopus will have an underinflated impact factor.
  • Comparison of Journal Citation Reports and Scopus Impact Factors for Ecology and Environmental Sciences Journals 22 January 2010 12:56 UTC www.istl.org [Source type: Academic]

)
2008 impact factor = A/B
.(Note that 2008 impact factors are actually published in 2009; they cannot be calculated until all of the 2008 publications had been received by the indexing agency.^ Unofficial 2008 Impact Factor .
  • BioMed Central | for authors | General FAQ 22 January 2010 12:56 UTC www.biomedcentral.com [Source type: Academic]

^ Journals that publish articles on botanical or zoological taxonomy may also have lower impact factors because they often rely on older references, and references to taxonomic names are not included in the references list at the ends of these papers ( Werner 2006 ).
  • Comparison of Journal Citation Reports and Scopus Impact Factors for Ecology and Environmental Sciences Journals 22 January 2010 12:56 UTC www.istl.org [Source type: Academic]

^ The impact factor of a journal may be artificially inflated when it frequently includes review articles and letters, and there is also a bias against articles that are not published in English.
  • Comparison of Journal Citation Reports and Scopus Impact Factors for Ecology and Environmental Sciences Journals 22 January 2010 12:56 UTC www.istl.org [Source type: Academic]

)
.New journals, which are indexed from their first published issue, will receive an impact factor after two years of indexing; in this case, the citations to the year prior to Volume 1, and the number of articles published in the year prior to Volume 1 are known zero values.^ The impact factor of a journal is calculated by dividing the references cited in one year by the number of citable articles published in the same journal over the previous two years.
  • Comparison of Journal Citation Reports and Scopus Impact Factors for Ecology and Environmental Sciences Journals 22 January 2010 12:56 UTC www.istl.org [Source type: Academic]

^ Alert me to new issues of the journal .
  • Journal impact factor: a brief review -- Garfield 161 (8): 979 -- Canadian Medical Association Journal 22 January 2010 12:56 UTC www.cmaj.ca [Source type: Academic]
  • Understanding the Limitations of the Journal Impact Factor -- Kurmis 85 (12): 2449 -- Journal of Bone and Joint Surgery 22 January 2010 12:56 UTC www.ejbjs.org [Source type: Academic]
  • The Impact of Growth Hormone/Insulin-Like Growth Factor-I Axis and Nocturnal Breathing Disorders on Cardiovascular Features of Adult Patients with Prader-Willi Syndrome -- Marzullo et al. 90 (10): 5639 -- Journal of Clinical Endocrinology & Metabolism 22 January 2010 12:56 UTC jcem.endojournals.org [Source type: Academic]

^ Journal impact factor: a brief review .
  • Journal impact factor: a brief review -- Garfield 161 (8): 979 -- Canadian Medical Association Journal 22 January 2010 12:56 UTC www.cmaj.ca [Source type: Academic]

.Journals that are indexed starting with a volume other than the first volume will not get an impact factor until they have been indexed for three years.^ Unofficial Impact Factors* for other BioMed Central journals .
  • BioMed Central | about us | General FAQ 22 January 2010 12:56 UTC www.biomedcentral.com [Source type: Academic]
  • BioMed Central | for authors | General FAQ 22 January 2010 12:56 UTC www.biomedcentral.com [Source type: Academic]

^ Journal Impact Factors - 1998 Scientific Journal Impact Factors 1998 From the "Journal Citation Reports" published by ISI This list is not complete !
  • Journal Impact Factors - 1998 22 January 2010 12:56 UTC www.upstate.edu [Source type: Academic]

^ Note that in several cases the figures are artificially low, as they are based on a single year of citation data rather than the usual two.
  • BioMed Central | about us | General FAQ 22 January 2010 12:56 UTC www.biomedcentral.com [Source type: Academic]
  • BioMed Central | for authors | General FAQ 22 January 2010 12:56 UTC www.biomedcentral.com [Source type: Academic]

.Annuals and other irregular publications, will sometimes publish no items in a particular year, affecting the count.^ For example, to calculate the unofficial impact factor for CytoJournal, we would need to count the total number of articles published in 2005 (the first full calendar year of publications by the journal), and the total number of times these articles were cited in the 2006 calendar year.
  • First CytoJournal Peer-Reviewer's Retreat in 2006 - Open access, peer-review, and impact factor Shidham VB, Sandweiss L, Atkinson BF - CytoJournal 22 January 2010 12:56 UTC www.cytojournal.com [Source type: Academic]

^ Callaham M, Wears RL, Weber E. Journal prestige, publication bias, and other characteristics associated with citation of published studies in peer-reviewed journals.
  • Understanding the Limitations of the Journal Impact Factor -- Kurmis 85 (12): 2449 -- Journal of Bone and Joint Surgery 22 January 2010 12:56 UTC www.ejbjs.org [Source type: Academic]

.The impact factor relates to a specific time period; it is possible to calculate it for any desired period and the Journal Citation Reports (JCR) also includes a 5-year impact factor.^ Journal impact factor: a brief review .
  • Journal impact factor: a brief review -- Garfield 161 (8): 979 -- Canadian Medical Association Journal 22 January 2010 12:56 UTC www.cmaj.ca [Source type: Academic]

^ Do journals published by BioMed Central have Impact Factors and are their citations tracked?
  • BioMed Central | about us | General FAQ 22 January 2010 12:56 UTC www.biomedcentral.com [Source type: Academic]

^ Hoeffel C. Journal impact factors [letter].
  • Journal impact factor: a brief review -- Garfield 161 (8): 979 -- Canadian Medical Association Journal 22 January 2010 12:56 UTC www.cmaj.ca [Source type: Academic]

[2] .The JCR shows rankings of journals by impact factor, if desired by discipline, such as organic chemistry or psychiatry.^ Journal impact factor: a brief review .
  • Journal impact factor: a brief review -- Garfield 161 (8): 979 -- Canadian Medical Association Journal 22 January 2010 12:56 UTC www.cmaj.ca [Source type: Academic]

^ Extension of the impact factor to cross-discipline journal comparison is also inappropriate.
  • Understanding the Limitations of the Journal Impact Factor -- Kurmis 85 (12): 2449 -- Journal of Bone and Joint Surgery 22 January 2010 12:56 UTC www.ejbjs.org [Source type: Academic]

^ Linde A. On the pitfalls of journal ranking by Impact Factor.
  • Understanding the Limitations of the Journal Impact Factor -- Kurmis 85 (12): 2449 -- Journal of Bone and Joint Surgery 22 January 2010 12:56 UTC www.ejbjs.org [Source type: Academic]

Use

The IF is used to compare different journals within a certain field. .The Web of Knowledge indexes 9000 science and social science journals from 60 countries and the results are widely (though not freely) available.^ In discussing the results of a review of German social science periodicals, Seglen 23 reported that only two of 542 such journals listed in a German database were included in the Science Citation Index.
  • Understanding the Limitations of the Journal Impact Factor -- Kurmis 85 (12): 2449 -- Journal of Bone and Joint Surgery 22 January 2010 12:56 UTC www.ejbjs.org [Source type: Academic]

^ The Science Citation Index, a commercial property of the Institute of Scientific Information (Philadelphia, Pennsylvania) 5 - 7 , is used to generate the Journal Citation Reports, produced annually.
  • Understanding the Limitations of the Journal Impact Factor -- Kurmis 85 (12): 2449 -- Journal of Bone and Joint Surgery 22 January 2010 12:56 UTC www.ejbjs.org [Source type: Academic]

^ Science and scholarship on the World Wide Web: a North American perspective.
  • Web Impact Factors for Iranian Universities 22 January 2010 12:56 UTC www.webology.ir [Source type: Academic]

In addition, the IF is an objective measure.

Criticisms

.Numerous criticisms have been made of the use of an impact factor.^ The Web Impact Factor: a critical review.
  • Web Impact Factors for Iranian Universities 22 January 2010 12:56 UTC www.webology.ir [Source type: Academic]

^ While impact factors may be useful for the qualitative evaluation of journals, the usefulness does not extend to individual articles.
  • Understanding the Limitations of the Journal Impact Factor -- Kurmis 85 (12): 2449 -- Journal of Bone and Joint Surgery 22 January 2010 12:56 UTC www.ejbjs.org [Source type: Academic]

^ Seglen PO. Why the impact factor of journals should not be used for evaluating research.
  • Understanding the Limitations of the Journal Impact Factor -- Kurmis 85 (12): 2449 -- Journal of Bone and Joint Surgery 22 January 2010 12:56 UTC www.ejbjs.org [Source type: Academic]

.Besides the more general debate on the usefulness of citation metrics, criticisms mainly concern the validity of the impact factor, possible manipulation, and its misuse.^ Saper CB. What's in a citation impact factor?
  • Understanding the Limitations of the Journal Impact Factor -- Kurmis 85 (12): 2449 -- Journal of Bone and Joint Surgery 22 January 2010 12:56 UTC www.ejbjs.org [Source type: Academic]

^ Many of the journals listed have very low impact factors, suggesting that a high citation rate alone may not be a key consideration for inclusion.
  • Understanding the Limitations of the Journal Impact Factor -- Kurmis 85 (12): 2449 -- Journal of Bone and Joint Surgery 22 January 2010 12:56 UTC www.ejbjs.org [Source type: Academic]

^ In a similar context, general journals tend to have higher impact factors than specialist journals 13 , 25 , 35 because of the larger pool for citation.
  • Understanding the Limitations of the Journal Impact Factor -- Kurmis 85 (12): 2449 -- Journal of Bone and Joint Surgery 22 January 2010 12:56 UTC www.ejbjs.org [Source type: Academic]

[3]

Validity

.
  • The impact factor is highly discipline-dependent.^ Extension of the impact factor to cross-discipline journal comparison is also inappropriate.
    • Understanding the Limitations of the Journal Impact Factor -- Kurmis 85 (12): 2449 -- Journal of Bone and Joint Surgery 22 January 2010 12:56 UTC www.ejbjs.org [Source type: Academic]

    .The percentage of total citations occurring in the first two years after publication varies highly among disciplines from 1-3 percent in the mathematical and physical sciences to 5-8 percent in the biological sciences.^ For example, to calculate the unofficial impact factor for CytoJournal, we would need to count the total number of articles published in 2005 (the first full calendar year of publications by the journal), and the total number of times these articles were cited in the 2006 calendar year.
    • First CytoJournal Peer-Reviewer's Retreat in 2006 - Open access, peer-review, and impact factor Shidham VB, Sandweiss L, Atkinson BF - CytoJournal 22 January 2010 12:56 UTC www.cytojournal.com [Source type: Academic]

    ^ To calculate even an unofficial impact factor, the journal needs to have been published for at least two calendar years (such unofficial factor calculation requires us to know the total number of publications in one year, and the number of times these articles were published in the following year).
    • First CytoJournal Peer-Reviewer's Retreat in 2006 - Open access, peer-review, and impact factor Shidham VB, Sandweiss L, Atkinson BF - CytoJournal 22 January 2010 12:56 UTC www.cytojournal.com [Source type: Academic]

    ^ The impact factor is calculated based on a three-year period by the following formula: A = Total number of times the articles published in a two year period (e.g.
    • First CytoJournal Peer-Reviewer's Retreat in 2006 - Open access, peer-review, and impact factor Shidham VB, Sandweiss L, Atkinson BF - CytoJournal 22 January 2010 12:56 UTC www.cytojournal.com [Source type: Academic]

    [4]
  • .
  • The impact factor could not be reproduced in an independent audit[5] (but see Thomson Scientific's reply[6]).
  • The impact factor refers to the average number of citations per paper, but this is not a normal distribution.^ The recursive impact factors are normalized so that the average citations has a weight of 1.
    • IDEAS/RePEc Recursive Impact Factors for Series and Journals 22 January 2010 12:56 UTC ideas.repec.org [Source type: Academic]
    • IDEAS/RePEc Recursive Discounted Impact Factors for Journals 22 January 2010 12:56 UTC ideas.repec.org [Source type: Academic]

    ^ Citation analysis and impact factor .
    • Evaluating E-Contents Beyond Impact Factor - A Pilot Study Selected Open Access Journals In Library And Information Science 22 January 2010 12:56 UTC quod.lib.umich.edu [Source type: Academic]

    ^ What about number of citations to the Editor's papers?
    • Impact Factor — Site 22 January 2010 12:56 UTC www.wame.org [Source type: Academic]

    It is rather a Bradford distribution, as predicted by theory. .Being an arithmetic mean, the impact factor therefore is not a valid representation of this distribution and unfit for citation evaluation.^ Saper CB. What's in a citation impact factor?
    • Understanding the Limitations of the Journal Impact Factor -- Kurmis 85 (12): 2449 -- Journal of Bone and Joint Surgery 22 January 2010 12:56 UTC www.ejbjs.org [Source type: Academic]

    ^ Probably nowadays the impact factor is the most popular and influential measurement to evaluate the people's quality of publications.

    ^ Many of the journals listed have very low impact factors, suggesting that a high citation rate alone may not be a key consideration for inclusion.
    • Understanding the Limitations of the Journal Impact Factor -- Kurmis 85 (12): 2449 -- Journal of Bone and Joint Surgery 22 January 2010 12:56 UTC www.ejbjs.org [Source type: Academic]

    [7]
  • .
  • In the short term - especially in the case of low-impact-factor journals - many of the citations to a certain article are made in papers written by the author(s) of the original article.^ Also for papers and articles: citation counts ( recent ) and simple discounted impact factors ( recent ).
    • IDEAS/RePEc Recursive Impact Factors for Series and Journals 22 January 2010 12:56 UTC ideas.repec.org [Source type: Academic]
    • IDEAS/RePEc Recursive Discounted Impact Factors for Journals 22 January 2010 12:56 UTC ideas.repec.org [Source type: Academic]

    ^ Journal impact factor: a brief review .
    • Journal impact factor: a brief review -- Garfield 161 (8): 979 -- Canadian Medical Association Journal 22 January 2010 12:56 UTC www.cmaj.ca [Source type: Academic]

    ^ Journal impact factors generally involve relatively large populations of articles and citations.
    • Journal impact factor: a brief review -- Garfield 161 (8): 979 -- Canadian Medical Association Journal 22 January 2010 12:56 UTC www.cmaj.ca [Source type: Academic]

    [8] .This means that counting citations may be independent of the real “impact” of the work among investigators.^ Many of the journals listed have very low impact factors, suggesting that a high citation rate alone may not be a key consideration for inclusion.
    • Understanding the Limitations of the Journal Impact Factor -- Kurmis 85 (12): 2449 -- Journal of Bone and Joint Surgery 22 January 2010 12:56 UTC www.ejbjs.org [Source type: Academic]

    ^ Recently published articles may not have had enough time to be cited, so it is tempting to use the impact factor as a surrogate, virtual count.
    • Journal impact factor: a brief review -- Garfield 161 (8): 979 -- Canadian Medical Association Journal 22 January 2010 12:56 UTC www.cmaj.ca [Source type: Academic]

    ^ The fact that a journal or article is available electronically 7 , 9 may also increase the rate of citation and thus the impact factor.
    • Understanding the Limitations of the Journal Impact Factor -- Kurmis 85 (12): 2449 -- Journal of Bone and Joint Surgery 22 January 2010 12:56 UTC www.ejbjs.org [Source type: Academic]

    .Garfield, however, maintains that this phenomenon hardly influences a journal's impact factor.^ Garfield E. Which medical journals have the greatest impact?
    • Understanding the Limitations of the Journal Impact Factor -- Kurmis 85 (12): 2449 -- Journal of Bone and Joint Surgery 22 January 2010 12:56 UTC www.ejbjs.org [Source type: Academic]

    ^ Garfield E. Journal impact factor: a brief review.
    • Understanding the Limitations of the Journal Impact Factor -- Kurmis 85 (12): 2449 -- Journal of Bone and Joint Surgery 22 January 2010 12:56 UTC www.ejbjs.org [Source type: Academic]

    ^ Many of the journals listed have very low impact factors, suggesting that a high citation rate alone may not be a key consideration for inclusion.
    • Understanding the Limitations of the Journal Impact Factor -- Kurmis 85 (12): 2449 -- Journal of Bone and Joint Surgery 22 January 2010 12:56 UTC www.ejbjs.org [Source type: Academic]

    [9] .However, a study of author self-citations in diabetes literature found that the frequency of author self-citation was not associated with the quality of publications.^ However, these authors note that studies of the impacts of accommodations on LEP students are scant.
    • Framing Impact Factors to Aid Limited-English-Proficient Students in Mathematics and Science 22 January 2010 12:56 UTC www.ncrel.org [Source type: FILTERED WITH BAYES]

    [10] .Similarly, journal self-citation is common in journals dealing in specialized topics having high overlap in readership and authors, and is not necessarily a sign of low quality or manipulation.^ If there is such a problem, then is it possible that an author could be equally devious by including a disproportionate number of citations to articles in the journal to which the current manuscript is being submitted?
    • Impact Factor — Site 22 January 2010 12:56 UTC www.wame.org [Source type: Academic]

    ^ The editor of a journal on haematology routinely sent authors a letter asking them to increase the number of citations to papers published in that journal.
    • Impact Factor — Site 22 January 2010 12:56 UTC www.wame.org [Source type: Academic]

    ^ Typically, when the author's bibliography is examined, a journal's impact factor is substituted for the actual citation count.
    • Journal impact factor: a brief review -- Garfield 161 (8): 979 -- Canadian Medical Association Journal 22 January 2010 12:56 UTC www.cmaj.ca [Source type: Academic]

    [11]

Manipulation

.A journal can adopt editorial policies that increase its impact factor.^ Journal impact factor: a brief review .
  • Journal impact factor: a brief review -- Garfield 161 (8): 979 -- Canadian Medical Association Journal 22 January 2010 12:56 UTC www.cmaj.ca [Source type: Academic]

^ Hoeffel C. Journal impact factors [letter].
  • Journal impact factor: a brief review -- Garfield 161 (8): 979 -- Canadian Medical Association Journal 22 January 2010 12:56 UTC www.cmaj.ca [Source type: Academic]

^ For journals that have not been tracked for long enough to have an Impact Factor, or are not yet tracked by Thomson Reuters(ISI), it is nonetheless possible to calculate a unofficial Impact Factor, which we have done for some journals.
  • BioMed Central | about us | General FAQ 22 January 2010 12:56 UTC www.biomedcentral.com [Source type: Academic]

[12] .These editorial policies may not solely involve improving the quality of published scientific work.^ These items (e.g., letters, news stories and editorials) are not included in JCR 's calculation of impact, yet we all know that they may be cited.
  • Journal impact factor: a brief review -- Garfield 161 (8): 979 -- Canadian Medical Association Journal 22 January 2010 12:56 UTC www.cmaj.ca [Source type: Academic]

^ Outside of the editorial and publishing world, the complex factors that affect impact factors, journal/article quality, and relevance are poorly understood.
  • Impact Factor — Site 22 January 2010 12:56 UTC www.wame.org [Source type: Academic]

^ Granting and other policy agencies often wish to bypass the work involved in obtaining actual citation counts for individual articles and authors.
  • Journal impact factor: a brief review -- Garfield 161 (8): 979 -- Canadian Medical Association Journal 22 January 2010 12:56 UTC www.cmaj.ca [Source type: Academic]

.
  • Journals may publish a larger percentage of review articles which generally are cited more than research reports.^ However, most journals publish primarily substantive research or review articles.
    • Journal impact factor: a brief review -- Garfield 161 (8): 979 -- Canadian Medical Association Journal 22 January 2010 12:56 UTC www.cmaj.ca [Source type: Academic]

    ^ Three of the e-journals publish refereed articles.
    • Evaluating E-Contents Beyond Impact Factor - A Pilot Study Selected Open Access Journals In Library And Information Science 22 January 2010 12:56 UTC quod.lib.umich.edu [Source type: Academic]

    ^ Journal Impact Factors - 1998 Scientific Journal Impact Factors 1998 From the "Journal Citation Reports" published by ISI This list is not complete !
    • Journal Impact Factors - 1998 22 January 2010 12:56 UTC www.upstate.edu [Source type: Academic]

    .Therefore review articles can raise the impact factor of the journal and review journals will therefore often have the highest impact factors in their respective fields.
  • Journals may change the fraction of "citable items" compared to front-matter in the denominator of the IF equation.^ The strong influence of these articles is clear when it is considered that journals that have been historically assigned the highest impact factors in each field tend to be the review journals.
    • Understanding the Limitations of the Journal Impact Factor -- Kurmis 85 (12): 2449 -- Journal of Bone and Joint Surgery 22 January 2010 12:56 UTC www.ejbjs.org [Source type: Academic]

    ^ The Web Impact Factor: a critical review.
    • Web Impact Factors for Iranian Universities 22 January 2010 12:56 UTC www.webology.ir [Source type: Academic]

    ^ The equation for calculation of the impact factor.
    • Understanding the Limitations of the Journal Impact Factor -- Kurmis 85 (12): 2449 -- Journal of Bone and Joint Surgery 22 January 2010 12:56 UTC www.ejbjs.org [Source type: Academic]

    .Which types of articles are considered "citable" is largely a matter of negotiation between journals and Thomson Scientific.^ To force somebody to cite articles from Journal X, Y or Z without considering how it would improve the scientific value of the paper is simply NONSENSE. .
    • Impact Factor — Site 22 January 2010 12:56 UTC www.wame.org [Source type: Academic]

    ^ Journal impact factors generally involve relatively large populations of articles and citations.
    • Journal impact factor: a brief review -- Garfield 161 (8): 979 -- Canadian Medical Association Journal 22 January 2010 12:56 UTC www.cmaj.ca [Source type: Academic]

    ^ Such journals publish large numbers of items that are neither traditional research nor review articles.
    • Journal impact factor: a brief review -- Garfield 161 (8): 979 -- Canadian Medical Association Journal 22 January 2010 12:56 UTC www.cmaj.ca [Source type: Academic]

    .As a result of such negotiations, impact factor variations of more than 300% have been observed.^ In a similar context, general journals tend to have higher impact factors than specialist journals 13 , 25 , 35 because of the larger pool for citation.
    • Understanding the Limitations of the Journal Impact Factor -- Kurmis 85 (12): 2449 -- Journal of Bone and Joint Surgery 22 January 2010 12:56 UTC www.ejbjs.org [Source type: Academic]

    ^ In a more extreme example, the recorded impact factor distribution 17 ranges from hundredths of a unit to > 40.
    • Understanding the Limitations of the Journal Impact Factor -- Kurmis 85 (12): 2449 -- Journal of Bone and Joint Surgery 22 January 2010 12:56 UTC www.ejbjs.org [Source type: Academic]

    ^ There are of course many other, more subtle methods for increasing the impact factor; however, as this paper is not intended to be a recipe for the unscrupulous, they will not be discussed here.
    • Understanding the Limitations of the Journal Impact Factor -- Kurmis 85 (12): 2449 -- Journal of Bone and Joint Surgery 22 January 2010 12:56 UTC www.ejbjs.org [Source type: Academic]

    [13] .For instance, editorials in a journal are not considered to be citable items and therefore do not enter into the denominator of the impact factor.^ Journal Impact Factors - 1998 Scientific Journal Impact Factors 1998 From the "Journal Citation Reports" published by ISI This list is not complete !
    • Journal Impact Factors - 1998 22 January 2010 12:56 UTC www.upstate.edu [Source type: Academic]

    ^ If you as a scientist seek funding - and apply to say a trust or govt research funder - the funders take into account, the impact factors of the journals you publish in.
    • Bad Science: Funding and findings: the impact factor | Comment is free | The Guardian 22 January 2010 12:56 UTC www.guardian.co.uk [Source type: FILTERED WITH BAYES]

    ^ I assume they are doing this to increase citations and thus boost the impact factors of their journals.
    • Impact Factor — Site 22 January 2010 12:56 UTC www.wame.org [Source type: Academic]

    .However, citations to such items will still enter into the numerator, thereby inflating the impact factor.^ Saper CB. What's in a citation impact factor?
    • Understanding the Limitations of the Journal Impact Factor -- Kurmis 85 (12): 2449 -- Journal of Bone and Joint Surgery 22 January 2010 12:56 UTC www.ejbjs.org [Source type: Academic]

    ^ Journal Impact Factors - 1998 Scientific Journal Impact Factors 1998 From the "Journal Citation Reports" published by ISI This list is not complete !
    • Journal Impact Factors - 1998 22 January 2010 12:56 UTC www.upstate.edu [Source type: Academic]

    ^ Many of the journals listed have very low impact factors, suggesting that a high citation rate alone may not be a key consideration for inclusion.
    • Understanding the Limitations of the Journal Impact Factor -- Kurmis 85 (12): 2449 -- Journal of Bone and Joint Surgery 22 January 2010 12:56 UTC www.ejbjs.org [Source type: Academic]

    .In addition, if such items cite other articles (often even from the same journal), those citations will be counted and will increase the citation count for the cited journal.^ [Medline] This article has been cited by other articles: .
    • Journal impact factor: a brief review -- Garfield 161 (8): 979 -- Canadian Medical Association Journal 22 January 2010 12:56 UTC www.cmaj.ca [Source type: Academic]

    ^ Calculated by the count of articles 2006-2007 divided by the count of citations to the corresponding articles .
    • Journal Impact Factors 22 January 2010 12:56 UTC www.helsinki.fi [Source type: Academic]

    ^ Recently published articles may not have had enough time to be cited, so it is tempting to use the impact factor as a surrogate, virtual count.
    • Journal impact factor: a brief review -- Garfield 161 (8): 979 -- Canadian Medical Association Journal 22 January 2010 12:56 UTC www.cmaj.ca [Source type: Academic]

    This effect is hard to evaluate, for the distinction between editorial comment and short original articles is not always obvious. ."Letters to the editor" might refer to either class.
  • Several methods, not necessarily with nefarious intent, exist for a journal to cite articles in the same journal which will increase the journal's impact factor.^ Journal Impact Factors - 1998 Scientific Journal Impact Factors 1998 From the "Journal Citation Reports" published by ISI This list is not complete !
    • Journal Impact Factors - 1998 22 January 2010 12:56 UTC www.upstate.edu [Source type: Academic]

    ^ Other well-recognized ways of increasing the impact factor of a journal include increasing the rate of self-citation, whereby articles published in a given journal make formal reference to other articles previously published in the same journal.
    • Understanding the Limitations of the Journal Impact Factor -- Kurmis 85 (12): 2449 -- Journal of Bone and Joint Surgery 22 January 2010 12:56 UTC www.ejbjs.org [Source type: Academic]

    ^ Many of the journals listed have very low impact factors, suggesting that a high citation rate alone may not be a key consideration for inclusion.
    • Understanding the Limitations of the Journal Impact Factor -- Kurmis 85 (12): 2449 -- Journal of Bone and Joint Surgery 22 January 2010 12:56 UTC www.ejbjs.org [Source type: Academic]

    [14]
  • .
  • In 2007 a specialist journal with an impact factor of 0.66 published an editorial that cited all its articles from 2005 to 2006 in a protest against the absurd use of the impact factor.^ HemmingssonA. The use of impact factors is becoming important for scientific journals.
    • Understanding the Limitations of the Journal Impact Factor -- Kurmis 85 (12): 2449 -- Journal of Bone and Joint Surgery 22 January 2010 12:56 UTC www.ejbjs.org [Source type: Academic]

    ^ IMPACT FACTORS 2007 .
    • Journal Impact Factors 22 January 2010 12:56 UTC www.helsinki.fi [Source type: Academic]

    ^ Do journals published by BioMed Central have Impact Factors and are their citations tracked?
    • BioMed Central | about us | General FAQ 22 January 2010 12:56 UTC www.biomedcentral.com [Source type: Academic]
    • BioMed Central | for authors | General FAQ 22 January 2010 12:56 UTC www.biomedcentral.com [Source type: Academic]

    [15] .The large number of citations meant that the impact factor for that journal increased to 1.44. As a result of the increase, the journal was not included in the 2008 Journal Citation Report.^ I assume they are doing this to increase citations and thus boost the impact factors of their journals.
    • Impact Factor — Site 22 January 2010 12:56 UTC www.wame.org [Source type: Academic]

    ^ Journal Impact Factors - 1998 Scientific Journal Impact Factors 1998 From the "Journal Citation Reports" published by ISI This list is not complete !
    • Journal Impact Factors - 1998 22 January 2010 12:56 UTC www.upstate.edu [Source type: Academic]

    ^ If there is such a problem, then is it possible that an author could be equally devious by including a disproportionate number of citations to articles in the journal to which the current manuscript is being submitted?
    • Impact Factor — Site 22 January 2010 12:56 UTC www.wame.org [Source type: Academic]

    [16]

Misuse

.
  • The impact factor is often misused to evaluate the importance of an individual publication or evaluate an individual researcher.^ The importance of precautionary motives in explaining individual and aggregate saving ," Carnegie-Rochester Conference Series on Public Policy , Elsevier, vol.
    • IDEAS/RePEc: Top 1‰ research items by number of citations, weighted by simple impact factors 22 January 2010 12:56 UTC ideas.repec.org [Source type: Academic]

    ^ IDEAS/RePEc: Top 1‰ research items by number of citations, weighted by simple impact factors .
    • IDEAS/RePEc: Top 1‰ research items by number of citations, weighted by simple impact factors 22 January 2010 12:56 UTC ideas.repec.org [Source type: Academic]

    ^ Top 1‰ research items by number of citations, weighted by simple impact factors .
    • IDEAS/RePEc: Top 1‰ research items by number of citations, weighted by simple impact factors 22 January 2010 12:56 UTC ideas.repec.org [Source type: Academic]

    [17] .This does not work well since a small number of publications are cited much more than the majority - for example, about 90% of Nature's 2004 impact factor was based on only a quarter of its publications, and thus the importance of any one publication will be different from, and in most cases less than, the overall number.^ Probably nowadays the impact factor is the most popular and influential measurement to evaluate the people's quality of publications.

    ^ Providing a marketing outlook on a particular commodity involves much more these days than simply looking at supply and demand numbers, says Chuck Danehower, University of Tennessee Extension farm management specialist.

    ^ Note that in several cases the figures are artificially low, as they are based on a single year of citation data rather than the usual two.
    • BioMed Central | about us | General FAQ 22 January 2010 12:56 UTC www.biomedcentral.com [Source type: Academic]

    [18] .The impact factor, however, averages over all articles and thus underestimates the citations of the most cited articles while exaggerating the number of citations of the majority of articles.^ The recursive impact factors are normalized so that the average citations has a weight of 1.
    • IDEAS/RePEc Recursive Impact Factors for Series and Journals 22 January 2010 12:56 UTC ideas.repec.org [Source type: Academic]
    • IDEAS/RePEc Recursive Discounted Impact Factors for Journals 22 January 2010 12:56 UTC ideas.repec.org [Source type: Academic]

    ^ Saper CB. What's in a citation impact factor?
    • Understanding the Limitations of the Journal Impact Factor -- Kurmis 85 (12): 2449 -- Journal of Bone and Joint Surgery 22 January 2010 12:56 UTC www.ejbjs.org [Source type: Academic]

    ^ Probably nowadays the impact factor is the most popular and influential measurement to evaluate the people's quality of publications.

    .Consequently, the Higher Education Funding Council for England was urged by the House of Commons Science and Technology Select Committee to remind Research Assessment Exercise panels that they are obliged to assess the quality of the content of individual articles, not the reputation of the journal in which they are published.^ There is evidence to suggest that some academic assessment committees and institutional promotion, tenure, and funding bodies have also adopted this tool for evaluation of individual researchers or research groups 3 , 5 , 8 , 10 , 11 , 14 , 15 , although just how widespread this practice is remains unclear.
    • Understanding the Limitations of the Journal Impact Factor -- Kurmis 85 (12): 2449 -- Journal of Bone and Joint Surgery 22 January 2010 12:56 UTC www.ejbjs.org [Source type: Academic]

    ^ Extension of the impact factor to the assessment of journal quality or individual authors is inappropriate.
    • Understanding the Limitations of the Journal Impact Factor -- Kurmis 85 (12): 2449 -- Journal of Bone and Joint Surgery 22 January 2010 12:56 UTC www.ejbjs.org [Source type: Academic]

    ^ I think the vaccine industry and their bad science lackeys will have to put their research house in order - and there is little chance of that - before the 'campaigners' will be convinced.
    • Bad Science: Funding and findings: the impact factor | Comment is free | The Guardian 22 January 2010 12:56 UTC www.guardian.co.uk [Source type: FILTERED WITH BAYES]

    [19]

Other measures of impact

Related indices

Some related values, also calculated and published by the same organization, are:
.
  • the immediacy index: the number of citations the articles in a journal receive in a given year divided by the number of articles published.
  • the cited half-life: the median age of the articles that were cited in Journal Citation Reports each year.^ The WIFs for Iranian universities were calculated by dividing link page counts by the number of pages found in AltaVista for each university at a given point in time.
    • Web Impact Factors for Iranian Universities 22 January 2010 12:56 UTC www.webology.ir [Source type: Academic]

    ^ However, the research unit of the Iranian Ministry of Science, Research & Technology writes a report entitled " Iran's national report on ranking universities based on their scholarly articles indexed by ISI " every year.
    • Web Impact Factors for Iranian Universities 22 January 2010 12:56 UTC www.webology.ir [Source type: Academic]

    ^ In other words, a WIF is the number of pages linking to a web site, divided by the number of pages in the web site at a given point in time.
    • Web Impact Factors for Iranian Universities 22 January 2010 12:56 UTC www.webology.ir [Source type: Academic]

    For example, if a journal's half-life in 2005 is 5, that means the citations from 2001-2005 are half of all the citations from that journal in 2005, and the other half of the citations precede 2001.[20]
  • the aggregate impact factor for a subject category: it is calculated taking into account the number of citations to all journals in the subject category and the number of articles from all the journals in the subject category.
.These measures apply only to journals, not individual articles or individual scientists (unlike the H-index).^ The strong influence of these articles is clear when it is considered that journals that have been historically assigned the highest impact factors in each field tend to be the review journals.
  • Understanding the Limitations of the Journal Impact Factor -- Kurmis 85 (12): 2449 -- Journal of Bone and Joint Surgery 22 January 2010 12:56 UTC www.ejbjs.org [Source type: Academic]

^ While impact factors may be useful for the qualitative evaluation of journals, the usefulness does not extend to individual articles.
  • Understanding the Limitations of the Journal Impact Factor -- Kurmis 85 (12): 2449 -- Journal of Bone and Joint Surgery 22 January 2010 12:56 UTC www.ejbjs.org [Source type: Academic]

^ If you as a scientist seek funding - and apply to say a trust or govt research funder - the funders take into account, the impact factors of the journals you publish in.
  • Bad Science: Funding and findings: the impact factor | Comment is free | The Guardian 22 January 2010 12:56 UTC www.guardian.co.uk [Source type: FILTERED WITH BAYES]

.The relative number of citations an individual article receives is better viewed as citation impact.^ Thus, increasing the number of review articles and technical reports per year and limiting the number of original research papers can bolster the impact factor.
  • Understanding the Limitations of the Journal Impact Factor -- Kurmis 85 (12): 2449 -- Journal of Bone and Joint Surgery 22 January 2010 12:56 UTC www.ejbjs.org [Source type: Academic]

^ While impact factors may be useful for the qualitative evaluation of journals, the usefulness does not extend to individual articles.
  • Understanding the Limitations of the Journal Impact Factor -- Kurmis 85 (12): 2449 -- Journal of Bone and Joint Surgery 22 January 2010 12:56 UTC www.ejbjs.org [Source type: Academic]

^ The fact that a journal or article is available electronically 7 , 9 may also increase the rate of citation and thus the impact factor.
  • Understanding the Limitations of the Journal Impact Factor -- Kurmis 85 (12): 2449 -- Journal of Bone and Joint Surgery 22 January 2010 12:56 UTC www.ejbjs.org [Source type: Academic]

.It is, however, possible to measure the Impact factor of the journals in which a particular person has published articles.^ Journal Impact Factors - 1998 Scientific Journal Impact Factors 1998 From the "Journal Citation Reports" published by ISI This list is not complete !
  • Journal Impact Factors - 1998 22 January 2010 12:56 UTC www.upstate.edu [Source type: Academic]

^ Probably nowadays the impact factor is the most popular and influential measurement to evaluate the people's quality of publications.

^ If you as a scientist seek funding - and apply to say a trust or govt research funder - the funders take into account, the impact factors of the journals you publish in.
  • Bad Science: Funding and findings: the impact factor | Comment is free | The Guardian 22 January 2010 12:56 UTC www.guardian.co.uk [Source type: FILTERED WITH BAYES]

This use is widespread, but controversial. .Garfield warns about the "misuse in evaluating individuals" because there is "a wide variation from article to article within a single journal".[9] Impact factors have a large, but controversial, influence on the way published scientific research is perceived and evaluated.^ While impact factors may be useful for the qualitative evaluation of journals, the usefulness does not extend to individual articles.
  • Understanding the Limitations of the Journal Impact Factor -- Kurmis 85 (12): 2449 -- Journal of Bone and Joint Surgery 22 January 2010 12:56 UTC www.ejbjs.org [Source type: Academic]

^ Seglen PO. Why the impact factor of journals should not be used for evaluating research.
  • Understanding the Limitations of the Journal Impact Factor -- Kurmis 85 (12): 2449 -- Journal of Bone and Joint Surgery 22 January 2010 12:56 UTC www.ejbjs.org [Source type: Academic]

^ Hansson S. Impact factor as a misleading tool in evaluation of medical journals.
  • Understanding the Limitations of the Journal Impact Factor -- Kurmis 85 (12): 2449 -- Journal of Bone and Joint Surgery 22 January 2010 12:56 UTC www.ejbjs.org [Source type: Academic]

PageRank algorithm

.In 1976 a recursive impact factor that gives citations from journals with high impact greater weight than citations from low-impact journals was proposed.^ The recursive impact factors are normalized so that the average citations has a weight of 1.
  • IDEAS/RePEc Recursive Impact Factors for Series and Journals 22 January 2010 12:56 UTC ideas.repec.org [Source type: Academic]
  • IDEAS/RePEc Recursive Discounted Impact Factors for Journals 22 January 2010 12:56 UTC ideas.repec.org [Source type: Academic]

^ If you as a scientist seek funding - and apply to say a trust or govt research funder - the funders take into account, the impact factors of the journals you publish in.
  • Bad Science: Funding and findings: the impact factor | Comment is free | The Guardian 22 January 2010 12:56 UTC www.guardian.co.uk [Source type: FILTERED WITH BAYES]

^ Also for papers and articles: citation counts ( recent ) and simple discounted impact factors ( recent ).
  • IDEAS/RePEc Recursive Impact Factors for Series and Journals 22 January 2010 12:56 UTC ideas.repec.org [Source type: Academic]
  • IDEAS/RePEc Recursive Discounted Impact Factors for Journals 22 January 2010 12:56 UTC ideas.repec.org [Source type: Academic]

[21] .Such a recursive impact factor resembles the PageRank algorithm of the Google search engine, though the original Pinski and Narin paper uses a "trade balance" approach in which journals score highest when they are often cited but rarely cite other journals.^ HemmingssonA. The use of impact factors is becoming important for scientific journals.
  • Understanding the Limitations of the Journal Impact Factor -- Kurmis 85 (12): 2449 -- Journal of Bone and Joint Surgery 22 January 2010 12:56 UTC www.ejbjs.org [Source type: Academic]

^ Jacso P. A deficiency in the algorithm for calculating the impact factor of scholarly journals: the Journal Impact Factor.
  • Understanding the Limitations of the Journal Impact Factor -- Kurmis 85 (12): 2449 -- Journal of Bone and Joint Surgery 22 January 2010 12:56 UTC www.ejbjs.org [Source type: Academic]

^ Web Impact Factors and search engine coverage.
  • Web Impact Factors for Iranian Universities 22 January 2010 12:56 UTC www.webology.ir [Source type: Academic]

A number of subsequent authors have proposed related approaches to ranking scholarly journals.[22][23][24] In 2006, Johan Bollen, Marko A. Rodriguez, and Herbert Van de Sompel also proposed using the PageRank algorithm.[25] From their paper:
ISI Impact Factor PageRank Combined
1 52.28 ANNU REV IMMUNOL 16.78 Nature 51.97 Nature
2 37.65 ANNU REV BIOCHEM 16.39 Journal of Biological Chemistry 48.78 Science
3 36.83 PHYSIOL REV 16.38 Science 19.84 New England Journal of Medicine
4 35.04 NAT REV MOL CELL BIO 14.49 PNAS 15.34 Cell
5 34.83 New England Journal of Medicine 8.41 PHYS REV LETT 14.88 PNAS
6 30.98 Nature 5.76 Cell 10.62 Journal of Biological Chemistry
7 30.55 Nature Medicine 5.70 New England Journal of Medicine 8.49 JAMA
8 29.78 Science 4.67 Journal of the American Chemical Society 7.78 The Lancet
9 28.18 NAT IMMUNOL 4.46 J IMMUNOL 7.56 NAT GENET
10 28.17 REV MOD PHYS 4.28 APPL PHYS LETT 6.53 Nature Medicine
.The table shows the top 10 journals by ISI Impact Factor, PageRank, and a modified system that combines the two (based on 2003 data).^ Journal Impact Factors - 1998 Scientific Journal Impact Factors 1998 From the "Journal Citation Reports" published by ISI This list is not complete !
  • Journal Impact Factors - 1998 22 January 2010 12:56 UTC www.upstate.edu [Source type: Academic]

^ Many of the journals listed have very low impact factors, suggesting that a high citation rate alone may not be a key consideration for inclusion.
  • Understanding the Limitations of the Journal Impact Factor -- Kurmis 85 (12): 2449 -- Journal of Bone and Joint Surgery 22 January 2010 12:56 UTC www.ejbjs.org [Source type: Academic]

^ Extension of the impact factor to the assessment of journal quality or individual authors is inappropriate.
  • Understanding the Limitations of the Journal Impact Factor -- Kurmis 85 (12): 2449 -- Journal of Bone and Joint Surgery 22 January 2010 12:56 UTC www.ejbjs.org [Source type: Academic]

.Nature and Science are generally regarded as the most prestigious journals, and in the combined system they come out on top.^ As a very general rule, journals with exceptionally high impact factors are among those widely considered the most prestigious 1 , 38 , although this is a subjective qualitative measure and does not consistently hold true.
  • Understanding the Limitations of the Journal Impact Factor -- Kurmis 85 (12): 2449 -- Journal of Bone and Joint Surgery 22 January 2010 12:56 UTC www.ejbjs.org [Source type: Academic]

^ The Science Citation Index, a commercial property of the Institute of Scientific Information (Philadelphia, Pennsylvania) 5 - 7 , is used to generate the Journal Citation Reports, produced annually.
  • Understanding the Limitations of the Journal Impact Factor -- Kurmis 85 (12): 2449 -- Journal of Bone and Joint Surgery 22 January 2010 12:56 UTC www.ejbjs.org [Source type: Academic]

^ Further, science in general is a good medium for making the most use of technology "since so much of it is hands-on" (Harris, 1995, p.
  • Framing Impact Factors to Aid Limited-English-Proficient Students in Mathematics and Science 22 January 2010 12:56 UTC www.ncrel.org [Source type: FILTERED WITH BAYES]

.The Eigenfactor is another PageRank-type measure of journal influence,[26] with rankings freely available online.^ Citations and links as a measure of effectiveness of online LIS journals .
  • Web Impact Factors for Iranian Universities 22 January 2010 12:56 UTC www.webology.ir [Source type: Academic]

^ The JIF measures citations made in journals published during one time period to articles published in another time period while the WIF is a " snapshot " of a search engine database at a specific time.
  • Web Impact Factors for Iranian Universities 22 January 2010 12:56 UTC www.webology.ir [Source type: Academic]

[27]

See also

  • H-index, for the impact factor of individual scientists, rather than journals.
  • PageRank, the algorithm used by Google, based on similar principles.
  • Eigenfactor, another journal citation ranking method.
  • SCImago Journal Rank, an open access journal metric which is based on Scopus data and uses an algorithm similar to PageRank.

References

  1. ^ "Introducing the Impact Factor". http://www.thomsonreuters.com/products_services/science/academic/impact_factor/. Retrieved 2009-08-26.  
  2. ^ "JCR with Eigenfactor". http://www.thomsonreuters.com/content/press_room/sci/350008. Retrieved 2009-08-26.  
  3. ^ "European Association of Science Editors statement on impact factors". http://www.ease.org.uk/statements/EASE_statement_on_impact_factors.shtml. Retrieved 2009-03-25.  
  4. ^ Erjen van Nierop (2009). "Why do statistics journals have low impact factors?". Statistica Neerlandica 63 (1): 52–62. doi:10.1111/j.1467-9574.2008.00408.x. http://www3.interscience.wiley.com/cgi-bin/fulltext/121630940/PDFSTART.  
  5. ^ Mike Rossner, Heather Van Epps, and Emma Hill (December 17, 2007). "Show me the data". Journal of Cell Biology. http://www.jcb.org/cgi/content/full/179/6/1091.  
  6. ^ "Thomson Scientific Corrects Inaccuracies In Editorial - Citation Impact Center - Thomson Reuters Forums". http://forums.thomsonscientific.com/ts/blog/article?message.uid=717. Retrieved 2009-08-31.  
  7. ^ Joint Committee on Quantitative Assessment of Research (June 12, 2008). "Citation Statistics" (PDF). International Mathematical Union. http://www.mathunion.org/fileadmin/IMU/Report/CitationStatistics.pdf.  
  8. ^ S.A. Marashi. On the identity of “citers”: are papers promptly recognized by other investigators? (2005) Med. Hypotheses 65, 822. PubMed:15990244.
  9. ^ a b Eugene Garfield (June 1998). "The Impact Factor and Using It Correctly". Der Unfallchirurg 101 (6): 413–414. PMID 9677838. http://www.garfield.library.upenn.edu/papers/derunfallchirurg_v101(6)p413y1998english.html.  
  10. ^ Gami AS, Montori VM, Wilczynski NL, Haynes RB (2004). "Author self-citation in the diabetes literature". CMAJ 170 (13): 1925–7. doi:10.1503/cmaj.1031879. PMID 15210641. http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pubmed&pubmedid=15210641.  
  11. ^ Natasa Kovacic and Aleksandra Misak (2004). "Author self-citation in medical literature". CMAJ 170 (13): 1929–30. doi:10.1503/cmaj.1040513. http://www.cmaj.ca/cgi/content/full/170/13/1929.  
  12. ^ Richard Monastersky (October 14, 2005). "The Number That's Devouring Science". The Chronicle of Higher Education. http://chronicle.com/free/v52/i08/08a01201.htm.  
  13. ^ PLoS Medicine Editors (June 6, 2006). "The Impact Factor Game". PLoS Medicine. doi:10.1371/journal.pmed.0030291.  
  14. ^ Fassoulaki A, Papilas K, Paraskeva A, Patris K (2002). "Impact factor bias and proposed adjustments for its determination". Acta Anaesthesiologica Scandinavica 46 (7): 902–5. doi:10.1034/j.1399-6576.2002.460723.x. PMID 12139549.  
  15. ^ Harm K. Schuttea, Jan G. Svec (2007). "Reaction of Folia Phoniatrica et Logopaedica on the Current Trend of Impact Factor Measures". Folia Phoniatrica et Logopaedica 59 (6): 281–285. doi:10.1159/000108334.  
  16. ^ "Journal Citation Reports - Notices". http://admin-apps.isiknowledge.com/JCR/static_html/notices/notices.htm. Retrieved 2009-09-24.  
  17. ^ Seglen PO (1997). "Why the impact factor of journals should not be used for evaluating research". BMJ 314 (7079): 498–502. PMID 9056804. PMC 2126010. http://www.bmj.com/cgi/content/full/314/7079/497.  
  18. ^ "Not-so-deep impact". Nature 435 (7045): 1003–4. 2005. doi:10.1038/4351003a. PMID 15973362.  
  19. ^ "House of Commons - Science and Technology - Tenth Report". 2004-07-07. http://www.publications.parliament.uk/pa/cm200304/cmselect/cmsctech/399/39912.htm. Retrieved 2008-07-28.  
  20. ^ Impact Factor, Immediacy Index, Cited Half-life
  21. ^ Gabriel Pinski and Francis Narin (1976). "Citation influence for journal aggregates of scientific publications: Theory with application to literature of physics". Information Processing & Management 12: 297–312. doi:10.1016/0306-4573(76)90048-0.  
  22. ^ S. J. Liebowitz and J. P. Palmer. (1984). "Assessing the relative impacts of economics journals". Journal of Economic Literature 22 (1): 77–88. http://www.jstor.org/pss/2725228.  
  23. ^ I. Palacios-Huerta and O. Volij (2004). "The measurement of intellectual influence". Econometrica 72: 963–977. doi:10.1111/j.1468-0262.2004.00519.x.  
  24. ^ Y. K. Kodrzycki and P. D. Yu (2006). "New approaches to ranking economics journals". B. E. Journal of Economics Analysis and Policy 5. doi:10.2202/1538-0645.1520.  
  25. ^ Johan Bollen, Marko A. Rodriguez, and Herbert Van de Sompel. (December 2006). "Journal Status". Scientometrics 69 (3). http://www.arxiv.org/abs/cs.GL/0601030.  
  26. ^ C. T. Bergstrom. (May 2007). "Eigenfactor: Measuring the value and prestige of scholarly journals". College & Research Libraries News 68 (5). http://www.ala.org/ala/mgrps/divs/acrl/publications/crlnews/2007/may/eigenfactor.cfm.  
  27. ^ eigenfactor.org

External links

.

The impact factor, often abbreviated IF, is a measure reflecting the average number of citations to articles published in science and social science journals. It is frequently used as a proxy for the relative importance of a journal within its field, with journals with higher impact factors deemed to be more important than those with lower ones. The impact factor was devised by Eugene Garfield, the founder of the Institute for Scientific Information (ISI), now part of Thomson Reuters. Impact factors are calculated yearly for those journals that are indexed in Thomson Reuter's Journal Citation Reports.

Contents

Calculation

In a given year, the impact factor of a journal is the average number of citations received per paper published in that journal during the two preceding years.[1] For example, if a journal has an impact factor of 3 in 2008, then its papers published in 2006 and 2007 received 3 citations each on average. The 2008 impact factor of a journal would be calculated as follows:

A = the number of times articles published in 2006 and 2007 were cited by indexed journals during 2008
B = the total number of "citable items" published by that journal in 2006 and 2007. ("Citable items" are usually articles, reviews, proceedings, or notes; not editorials or Letters-to-the-Editor.)
2008 impact factor = A/B

(Note that 2008 impact factors are actually published in 2009; they cannot be calculated until all of the 2008 publications have been processed by the indexing agency.)

New journals, which are indexed from their first published issue, will receive an impact factor after two years of indexing; in this case, the citations to the year prior to Volume 1, and the number of articles published in the year prior to Volume 1 are known zero values. Journals that are indexed starting with a volume other than the first volume will not get an impact factor until they have been indexed for three years. Annuals and other irregular publications, will sometimes publish no items in a particular year, affecting the count. The impact factor relates to a specific time period; it is possible to calculate it for any desired period and the Journal Citation Reports (JCR) also includes a 5-year impact factor.[2] The JCR shows rankings of journals by impact factor, if desired by discipline, such as organic chemistry or psychiatry.

Use

The IF is used to compare different journals within a certain field. The ISI Web of Knowledge indexes more than 11,000 science and social science journals,[3] and the results are widely (though not freely) available.

Criticisms

Numerous criticisms have been made of the use of an impact factor. Besides the more general debate on the usefulness of citation metrics, criticisms mainly concern the validity of the impact factor, possible manipulation, and its misuse.[4]

Validity

  • The impact factor is highly discipline-dependent. The percentage of total citations occurring in the first two years after publication varies highly among disciplines from 1-3 percent in the mathematical and physical sciences to 5-8 percent in the biological sciences.[5]
  • The impact factor could not be reproduced in an independent audit[6] (but see Thomson Scientific's reply[7]).
  • The impact factor refers to the average number of citations per paper, but this is not a normal distribution. It is rather a Bradford distribution, as predicted by theory. Being an arithmetic mean, the impact factor therefore is not a valid representation of this distribution and unfit for citation evaluation.[8]
  • In the short term - especially in the case of low-impact-factor journals - many of the citations to a certain article are made in papers written by the author(s) of the original article.[9] This means that counting citations may be independent of the real “impact” of the work among investigators. Garfield, however, maintains that this phenomenon hardly influences a journal's impact factor.[10] However, a study of author self-citations in diabetes literature found that the frequency of author self-citation was not associated with the quality of publications.[11] Similarly, journal self-citation is common in journals dealing in specialized topics having high overlap in readership and authors, and is not necessarily a sign of low quality or manipulation.[12]

Manipulation

A journal can adopt editorial policies that increase its impact factor[13] [14]. These editorial policies may not solely involve improving the quality of published scientific work.

  • Journals may publish a larger percentage of review articles which generally are cited more than research reports.[citation needed] Therefore review articles can raise the impact factor of the journal and review journals will therefore often have the highest impact factors in their respective fields.
  • Journals may change the fraction of "citable items" compared to front-matter in the denominator of the IF equation. Which types of articles are considered "citable" is largely a matter of negotiation between journals and Thomson Scientific. As a result of such negotiations, impact factor variations of more than 300% have been observed.[15] For instance, editorials in a journal are not considered to be citable items and therefore do not enter into the denominator of the impact factor. However, citations to such items will still enter into the numerator, thereby inflating the impact factor. In addition, if such items cite other articles (often even from the same journal), those citations will be counted and will increase the citation count for the cited journal. This effect is hard to evaluate, for the distinction between editorial comment and short original articles is not always obvious. "Letters to the editor" might refer to either class.
  • Several methods, not necessarily with nefarious intent, exist for a journal to cite articles in the same journal which will increase the journal's impact factor.[16][17]
  • In 2007, a specialist journal with an impact factor of 0.66 published an editorial that cited all its articles from 2005 to 2006 in a protest against the absurd use of the impact factor.[18] The large number of citations meant that the impact factor for that journal increased to 1.44. As a result of the increase, the journal was not included in the 2008 Journal Citation Report.[19]

Misuse

  • The impact factor is often misused to evaluate the importance of an individual publication or evaluate an individual researcher.[20] This does not work well since a small number of publications are cited much more than the majority - for example, about 90% of Nature's 2004 impact factor was based on only a quarter of its publications, and thus the importance of any one publication will be different from, and in most cases less than, the overall number.[21] The impact factor, however, averages over all articles and thus underestimates the citations of the most cited articles while exaggerating the number of citations of the majority of articles. Consequently, the Higher Education Funding Council for England was urged by the House of Commons Science and Technology Select Committee to remind Research Assessment Exercise panels that they are obliged to assess the quality of the content of individual articles, not the reputation of the journal in which they are published.[22]

Responses

  • Because “the impact factor is not always a reliable instrument” in November 2007 the European Association of Science Editors (EASE) issued an official statement recommending “that journal impact factors are used only - and cautiously - for measuring and comparing the influence of entire journals, but not for the assessment of single papers, and certainly not for the assessment of researchers or research programmes."[4]
  • In February 2010, the Deutsche Forschungsgemeinschaft (German Foundation for Science) published new guidelines to evaluate only articles and no bibliometric information on candidates to be evaluated in all decisions concerning "...performance-based funding allocations, postdoctoral qualifications, appointments, or reviewing funding proposals, [where] increasing importance has been given to numerical indicators such as the H-index and the impact factor."[23] This decision follows similar ones of the National Science Foundation (US) or the Research Assessment Exercise (UK).[citation needed]

Other measures of impact

Related indices

Some related values, also calculated and published by the same organization, are:

  • the immediacy index: the number of citations the articles in a journal receive in a given year divided by the number of articles published.
  • the cited half-life: the median age of the articles that were cited in Journal Citation Reports each year. For example, if a journal's half-life in 2005 is 5, that means the citations from 2001-2005 are half of all the citations from that journal in 2005, and the other half of the citations precede 2001.[24]
  • the aggregate impact factor for a subject category: it is calculated taking into account the number of citations to all journals in the subject category and the number of articles from all the journals in the subject category.

These measures apply only to journals, not individual articles or individual scientists (unlike the H-index). The relative number of citations an individual article receives is better viewed as citation impact.

It is, however, possible to measure the Impact factor of the journals in which a particular person has published articles. This use is widespread, but controversial. Garfield warns about the "misuse in evaluating individuals" because there is "a wide variation from article to article within a single journal".[10] Impact factors have a large, but controversial, influence on the way published scientific research is perceived and evaluated.

PageRank algorithm

In 1976 a recursive impact factor that gives citations from journals with high impact greater weight than citations from low-impact journals was proposed.[25] Such a recursive impact factor resembles the PageRank algorithm of the Google search engine, though the original Pinski and Narin paper uses a "trade balance" approach in which journals score highest when they are often cited but rarely cite other journals. A number of subsequent authors have proposed related approaches to ranking scholarly journals.[26][27][28] In 2006, Johan Bollen, Marko A. Rodriguez, and Herbert Van de Sompel also proposed using the PageRank algorithm.[29] From their paper:

ISI Impact Factor PageRank Combined
1 52.28 ANNU REV IMMUNOL 16.78 Nature 51.97 Nature
2 37.65 ANNU REV BIOCHEM 16.39 Journal of Biological Chemistry 48.78 Science
3 36.83 PHYSIOL REV 16.38 Science 19.84 New England Journal of Medicine
4 35.04 NAT REV MOL CELL BIO 14.49 PNAS 15.34 Cell
5 34.83 New England Journal of Medicine 8.41 PHYS REV LETT 14.88 PNAS
6 30.98 Nature 5.76 Cell 10.62 Journal of Biological Chemistry
7 30.55 Nature Medicine 5.70 New England Journal of Medicine 8.49 JAMA
8 29.78 Science 4.67 Journal of the American Chemical Society 7.78 The Lancet
9 28.18 NAT IMMUNOL 4.46 J IMMUNOL 7.56 NAT GENET
10 28.17 REV MOD PHYS 4.28 APPL PHYS LETT 6.53 Nature Medicine

The table shows the top 10 journals by ISI Impact Factor, PageRank, and a modified system that combines the two (based on 2003 data). Nature and Science are generally regarded as the most prestigious journals, and in the combined system they come out on top.

The Eigenfactor is another PageRank-type measure of journal influence,[30] with rankings freely available online.[31]

Article Level Metrics

Starting in March 2009, the Public Library of Science introduced "article level metrics[32] on every article in all of their titles.

See also

  • H-index, for the impact factor of individual scientists, rather than journals.
  • PageRank, the algorithm used by Google, based on similar principles.
  • Eigenfactor, another journal citation ranking method.
  • SCImago Journal Rank, an open access journal metric which is based on Scopus data and uses an algorithm similar to PageRank.

References

  1. ^ "Introducing the Impact Factor". http://www.thomsonreuters.com/products_services/science/academic/impact_factor/. Retrieved 2009-08-26. 
  2. ^ "JCR with Eigenfactor". http://www.thomsonreuters.com/content/press_room/sci/350008. Retrieved 2009-08-26. 
  3. ^ "Web of Knowledge > Real Facts > Quality and Quantity". http://wokinfo.com/realfacts/qualityandquantity/. Retrieved 2010-05-05. 
  4. ^ a b "European Association of Science Editors statement on impact factors". http://www.ease.org.uk/statements/EASE_statement_on_impact_factors.shtml. Retrieved 2009-03-25. 
  5. ^ Erjen van Nierop (2009). "Why do statistics journals have low impact factors?". Statistica Neerlandica 63 (1): 52–62. doi:10.1111/j.1467-9574.2008.00408.x. http://www3.interscience.wiley.com/cgi-bin/fulltext/121630940/PDFSTART. 
  6. ^ Mike Rossner, Heather Van Epps, and Emma Hill (December 17, 2007). "Show me the data". Journal of Cell Biology. http://www.jcb.org/cgi/content/full/179/6/1091. 
  7. ^ "Thomson Scientific Corrects Inaccuracies In Editorial - Citation Impact Center - Thomson Reuters Forums". http://forums.thomsonscientific.com/ts/blog/article?message.uid=717. Retrieved 2009-08-31. 
  8. ^ Joint Committee on Quantitative Assessment of Research (June 12, 2008). "Citation Statistics" (PDF). International Mathematical Union. http://www.mathunion.org/fileadmin/IMU/Report/CitationStatistics.pdf. 
  9. ^ S.A. Marashi. On the identity of “citers”: are papers promptly recognized by other investigators? (2005) Med. Hypotheses 65, 822. PubMed:15990244.
  10. ^ a b Eugene Garfield (June 1998). "The Impact Factor and Using It Correctly". Der Unfallchirurg 101 (6): 413–414. PMID 9677838. http://www.garfield.library.upenn.edu/papers/derunfallchirurg_v101(6)p413y1998english.html. 
  11. ^ Gami AS, Montori VM, Wilczynski NL, Haynes RB (2004). "Author self-citation in the diabetes literature". CMAJ 170 (13): 1925–7. doi:10.1503/cmaj.1031879. PMID 15210641. PMC 421720. http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pubmed&pubmedid=15210641. 
  12. ^ Natasa Kovacic and Aleksandra Misak (2004). "Author self-citation in medical literature". CMAJ 170 (13): 1929–30. doi:10.1503/cmaj.1040513. http://www.cmaj.ca/cgi/content/full/170/13/1929. 
  13. ^ Richard Monastersky (October 14, 2005). "The Number That's Devouring Science". The Chronicle of Higher Education. http://chronicle.com/free/v52/i08/08a01201.htm. 
  14. ^ Douglas N. Arnold; Kristine K. Fowler. "Nefarious Numbers". arΧiv:1010.0278. 
  15. ^ PLoS Medicine Editors (June 6, 2006). [Expression error: Unexpected < operator "The Impact Factor Game"]. PLoS Medicine (PLoS Medicine) 3 (6): e291. doi:10.1371/journal.pmed.0030291. PMID 16749869. 
  16. ^ Agrawal A (2005). "Corruption of Journal Impact Factors". Trends in Ecology and Evolution 20 (4): 157. doi:10.1016/j.tree.2005.02.002. PMID 16701362. http://www.eeb.cornell.edu/agrawal/research/papers/other%20pdfs/agrawal%202005%20tree%20corruption.pdf. 
  17. ^ Fassoulaki A, Papilas K, Paraskeva A, Patris K (2002). [Expression error: Unexpected < operator "Impact factor bias and proposed adjustments for its determination"]. Acta Anaesthesiologica Scandinavica 46 (7): 902–5. doi:10.1034/j.1399-6576.2002.460723.x. PMID 12139549. 
  18. ^ Harm K. Schuttea, Jan G. Svec (2007). [Expression error: Unexpected < operator "Reaction of Folia Phoniatrica et Logopaedica on the Current Trend of Impact Factor Measures"]. Folia Phoniatrica et Logopaedica 59 (6): 281–285. doi:10.1159/000108334. PMID 17965570. 
  19. ^ "Journal Citation Reports - Notices". http://admin-apps.isiknowledge.com/JCR/static_html/notices/notices.htm. Retrieved 2009-09-24. 
  20. ^ Seglen PO (1997). "Why the impact factor of journals should not be used for evaluating research". BMJ 314 (7079): 498–502. PMID 9056804. PMC 2126010. http://www.bmj.com/cgi/content/full/314/7079/497. 
  21. ^ [Expression error: Unexpected < operator "Not-so-deep impact"]. Nature 435 (7045): 1003–4. 2005. doi:10.1038/4351003a. PMID 15973362. 
  22. ^ "House of Commons - Science and Technology - Tenth Report". 2004-07-07. http://www.publications.parliament.uk/pa/cm200304/cmselect/cmsctech/399/39912.htm. Retrieved 2008-07-28. 
  23. ^ DFG press release (http://www.dfg.de/en/service/press/press_releases/2010/pressemitteilung_nr_07/index.html)
  24. ^ Impact Factor, Immediacy Index, Cited Half-life
  25. ^ Gabriel Pinski and Francis Narin (1976). [Expression error: Unexpected < operator "Citation influence for journal aggregates of scientific publications: Theory with application to literature of physics"]. Information Processing & Management 12: 297–312. doi:10.1016/0306-4573(76)90048-0. 
  26. ^ S. J. Liebowitz and J. P. Palmer. (1984). "Assessing the relative impacts of economics journals". Journal of Economic Literature (American Economic Association) 22 (1): 77–88. http://www.jstor.org/pss/2725228. 
  27. ^ I. Palacios-Huerta and O. Volij (2004). [Expression error: Unexpected < operator "The measurement of intellectual influence"]. Econometrica 72: 963–977. doi:10.1111/j.1468-0262.2004.00519.x. 
  28. ^ Y. K. Kodrzycki and P. D. Yu (2006). [Expression error: Unexpected < operator "New approaches to ranking economics journals"]. B. E. Journal of Economics Analysis and Policy 5. doi:10.2202/1538-0645.1520. 
  29. ^ Johan Bollen, Marko A. Rodriguez, and Herbert Van de Sompel. (December 2006). "Journal Status". Scientometrics 69 (3). http://www.arxiv.org/abs/cs.GL/0601030. 
  30. ^ C. T. Bergstrom. (May 2007). "Eigenfactor: Measuring the value and prestige of scholarly journals". College & Research Libraries News 68 (5). http://www.ala.org/ala/mgrps/divs/acrl/publications/crlnews/2007/may/eigenfactor.cfm. 
  31. ^ eigenfactor.org
  32. ^ Article-Level Metrics Information

External links


Citable sentences

Up to date as of December 29, 2010

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