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Year : 2016  |  Volume : 2  |  Issue : 2  |  Page : 63-64

Journal impact factor: Does it really have an impact?

Department of General Medicine, Pondicherry Institute of Medical Sciences, Kalapet, Puducherry, India

Date of Web Publication13-Jan-2017

Correspondence Address:
Aneesh Basheer
Department of General Medicine, Pondicherry Institute of Medical Sciences, Kalapet, Puducherry
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/2455-3069.198378

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How to cite this article:
Basheer A. Journal impact factor: Does it really have an impact?. J Curr Res Sci Med 2016;2:63-4

How to cite this URL:
Basheer A. Journal impact factor: Does it really have an impact?. J Curr Res Sci Med [serial online] 2016 [cited 2023 May 29];2:63-4. Available from: https://www.jcrsmed.org/text.asp?2016/2/2/63/198378

Medical professionals are under increasing pressure to publish, thanks to most universities and regulatory bodies mandating minimum criteria for promotions and incentives. Research has become a major component of routine activities of medical professionals, particularly in India over the last decade or so. Very frequently, good quality research culminates in publication. The investigators or authors base their choice of journals for publication on several points. The popularity and standing of the journal in its respective area of focus is a major determinant. Over the years, several indicators have been used to judge the quality and visibility of a journal. Impact factor (IF) is currently one of the most widely used such indicator.

Introduced in 1955 and popularized in the 1970s, IF remains the most commonly used indicator of research quality worldwide.[1] IF of a journal is calculated as a ratio of the number of citations to that journal in the preceding 2 years to the number of citable articles published in that journal during the same period. In other words, it reflects the frequency of citation of its articles in various journals in a given period. This magic number corrected to three decimal points is believed to reflect the journal's influence in research and evidence gathering. One advantage of the IF is its dynamic nature; it can easily be updated every 2 years. A study that assessed viewpoints of former editors of seven medical journals (all of them with high IFs) found that editors were generally happy that the IF of their journals steadily increased over time; however, not all of them were agreeable to the use of IF as the sole measure to judge the impact of research.[2] The removal of IF data recently from the websites of some major microbiology journals affiliated to the American Society of Microbiology may be testimony to this.[3]

The major source of criticism to the use of IF lies within itself. The numerator of IF includes all citations to that journal (whether it be original research articles, case reports, reviews, editorials, letters to the editor, or commentaries) whereas the denominator is comprised only citable articles published in that journal (which by definition includes only original research and reviews).[4] Many high IF journals do not publish articles other than original papers and reviews; case reports are published if exceptionally unique. Hence, the denominator for calculating IF for these journals remains small. However, many of the so-called noncitable articles (especially from prestigious journals) are cited and get added to the numerator while being excluded from the denominator for calculating IF of these journals.[5] It is obvious from this calculation that very often the numerator exceeds the denominator giving rise to a high IF. Consequent to the fact that much original work and reviews including landmark papers have already been published in these high impact journals (most of which are in vogue for several decades now), researchers tend to cite them far more frequently than others (particularly those established not very long back), thus exaggerating the numerator. The final result is a trend toward steady increase in IF of high impact journals.

IF also has other weaknesses. A major factor that may contribute to high IF of a journal is its self-citation rate. Self-citation can be assessed using self-citing rate and self-cited rate. Self-citing rate is estimated by the number of references in a journal to its own articles relative to the total number of references in the journal over a specified time period. Self-cited rate is the number of self-citations relative to the number of times it is cited by other journals in the same discipline, including itself. A study of self-citation in six anesthesia journals revealed self-citing rate as high as 57% and self-cited rate of 35%.[6] The same study found a significant positive correlation (r = 0.899; P = 0.015) between self-citing rates and IFs of all the six journals that were studied. Self-citation itself may be the result of several factors including author's preference to publish in journals that have already published similar or related work and the narrow scope of the journal which makes it difficult to cite from literature published in multidisciplinary journals.[6],[7] The issue of self-citation has gained so much attention that a recent work in PLOS proposed a new parameter, IF biased self-citation practices (IFBSCP) and speculate that a high IFBSCP may be due to coercive self-citation and excessive citation of the journal's own articles in its editorials.[8],[9]

One important factor determining the IF is affiliation of the journal to reputed scientific societies. A study of IFs of 17 nephrology and urology journals found that affiliation to a society was associated with a high IF.[10] The positive effect of self-citation on IF was reproduced in this study as well. Journals publishing retrospective studies were associated with a negative effect on the IF.[10] Inclusion of noncitable articles in the denominator resulted in dramatic changes in the IF of these journals.

Another drawback of the IF is its poor correlation with type of studies published; this has many implications. First, several studies have shown that articles dealing with clinical trials and systematic reviews (that constitute the apex of the pyramid of hierarchy of evidence) did not independently predict a high IF.[10],[11],[12] This indicates the fallacy of using IF to select best and reliable sources of evidence for clinical decision-making. In simple terms, a journal with high IF need not be publishing articles that provide evidence for major changes in diagnostic or therapeutic algorithms. Second, the IF does not predict how many times an article published in a particular journal will be cited. Third, a high IF guarantees benefit for all authors publishing in that journal, irrespective of the quality of research they have done individually. This further stresses the irrelevance of using IF to decide on individual performances, incentives, and promotions.

There also appears to be a regional clustering of high IF journals to the developed world (North America and Europe) with over fifty top ranking journals being published from these regions. Further, the IF is only calculated for journals indexed by Web of Science (Thomson Reuters), comprising 15% of all active scientific journals.[13] Time window of 2 years may be insufficient to assess the impact of a journal or its articles. This has led to proposals for a 5-year IF by several researchers and bibliometric experts. Moreover, number of citations does not follow normal distribution; calculation of IF based on mean citations for 2 years, therefore, violates statistical principles as well.[14]

Despite all the shortcomings, IF continues to influence research and publication practices worldwide. Several new complimentary indices such as Eigenfactor score and SCImago journal rank indicator have been introduced in recent years by databases such as ISI and SCOPUS. These offer the advantages of using databases that index a larger number of journals, a longer time period, and including all types of articles in calculation.[15] Further, several experts have suggested modifications to the calculation of IF, with inclusion of noncitable articles also in denominator, exclusion of or using adjustment factor for self-citation, and widening the time window for estimation to 5 years or more. Since no single index can serve as a wholesome indicator of journal quality and impact, the use of multiple indices and modification of IF would be the best way forward for the scientific community.

  References Top

Garfield E. Citation indexes for science; a new dimension in documentation through association of ideas. Science 1955;122:108-11.  Back to cited text no. 1
Chew M, Villanueva EV, Van Der Weyden MB. Life and times of the impact factor: Retrospective analysis of trends for seven medical journals (1994-2005) and their editors' views. J R Soc Med 2007;100:142-50.  Back to cited text no. 2
Casadevall A, Bertuzzi S, Buchmeier MJ, Davis RJ, Drake H, Fang FC, et al. ASM journals eliminate impact factor information from journal websites. Microbiol Mol Biol Rev 2016;80:i-ii.  Back to cited text no. 3
Liu XL. Structural characteristics of impact factors of the ten top international journals. Acta Editologica 2014;26:296-300.  Back to cited text no. 4
Liu XL, Gai SS, Zhang SL, Zhou J. Citation characteristics of non-citable documents and their contribution to journal impact factor. Acta Editologica 2015;27:495-9.  Back to cited text no. 5
Fassoulaki A, Paraskeva A, Papilas K, Karabinis G. Self-citations in six anaesthesia journals and their significance in determining the impact factor. Br J Anaesth 2000;84:266-9.  Back to cited text no. 6
Institute for Scientific Information. Science Citation Index, Journal Citation Reports. Philadelphia, Pennsylvania, USA: Institute for Scientific Information; 1997.  Back to cited text no. 7
Mahian O, Wongwises S. Is it ethical for journals to request self-citation? Sci Eng Ethics 2015;21:531-3.  Back to cited text no. 8
Campanario JM, González L. Journal self-citations that contribute to the impact factor: Documents labeled “editorial material” in journals covered by the science citation index. Scientometrics 2006;69:365-86.  Back to cited text no. 9
Sewell JM, Adejoro OO, Fleck JR, Wolfson JA, Konety BR. Factors associated with the journal impact factor (JIF) for urology and nephrology journals. Int Braz J Urol 2015;41:1058-66.  Back to cited text no. 10
Carpenter CR, Cone DC, Sarli CC. Using publication metrics to highlight academic productivity and research impact. Acad Emerg Med 2014;21:1160-72.  Back to cited text no. 11
Nielsen MB, Seitz K. Impact factors and prediction of popular topics in a journal. Ultraschall Med 2016;37:343-5.  Back to cited text no. 12
ProQuest. Ulrichsweb Global Serials Directory. Institutional Access Only. Homepage. Available from: http://www.ulrichsweb.serialssolutions.com/login. [Last accessed on 2014 Jul 18].  Back to cited text no. 13
Liu XL, Gai SS, Zhang SL, Wang P. An analysis of peer-reviewed scores and impact factors with different citation time windows: A case study of 28 ophthalmologic journals. PLoS One 2015;10:e0135583.  Back to cited text no. 14
Ramin S, Sarraf Shirazi A. Comparison between Impact factor, SCImago journal rank indicator and eigenfactor score of nuclear medicine journals. Nucl Med Rev Cent East Eur 2012;15:132-6.  Back to cited text no. 15

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