Is "Impact" the "Factor" that matters…? (Part I).

Eugene Garfield first wrote about impact factor in Science magazine in 1955.[1] In 1961 Science Citation Index was published. Sher and Garfield created the journal impact factor to select journals for the new Science Citation Index (SCI). Another publication by Garfield in 1972 in Science on “Citation Analysis as a tool in journal evaluation,” has been one of the most followed papers on this subject.[2]

The 'impact factor' (IF) refers to statistics calculated and published by Thomson Reuters as Journal Citation Reports (JCR). Calculation of an impact factor (IF) requires the total number of citations to the articles (the numerator) and the total number of articles published (the denominator) within specific time periods.

JCR gives a two-year impact factor and uses very specific time periods of publications and citations. The citation window here is the impact factor year, and the publication window refers to the two previous years.

The 2017 JCR impact factors (to be released in 2018) would be calculated as:

Impact factor is an important parameter used in the dental, medical, and scientific fields to compare journals. I must stress here that it is a bibliometric indicator for the journals only.

The IF is a bibliometric indicator, which should be used carefully, as a lot of variables play an important role in deciding the final impact factor. Use of IF without knowing the intricacies associated with it and factors that play a major role in manipulating it, may lead to conclusions that may not reveal the accurate picture. Criticisms against ignorant use of IF have been well recognized.[34]

Let me briefly touch on factors that have a huge impact on impact factors.

There are subject variations. Different subjects may have diverse levels and patterns of citation activity. History, Economics, Mathematics or Sociology journals may not have same levels of citations as medicine, chemistry or cell biology. The lower impact factor of journals of History, Economics, Mathematics or Sociology does not make them inferior. Within related subjects, for example, medicine, oncology, orthopedics, dentistry also may have variations in their impact factors. The impact factor for New England Journal Of Medicine in 2016 was 72.406 and for CA-A Cancer Journal For Clinicians was 187.040. You can't compare IFs of cancer journal to medicine journal (with in related subjects also). No way is New England Journal Of Medicine inferior to CA-A Cancer Journal For Clinicians jusy because its impact fator is less.

IFs are strongly biased towards journals which publish review articles. Periodontology 2000 will always have higher IF than any clinical journal as Periodontology 2000 only published review articles. As you would agree with me that review articles are read more and cited more.

The availaibilty of a particular journal influences IFs. The availability of journals as open access also may have a role to play in journal IFs. Availibility of journals in the package your intitution subscibes to affects IFs. You tend to cite journals which are available in your library for referral. Also within the subject, the widespead availiabilty of specific journals may have role to play in affecting IFs. For example, out of Periodontology journals, there will be maximum availability of Journal of Periodontology (AAP), Journal of Clinical Periodontology (JCP), Periodontology 2000 and and may be Journal of Periodontal Research (JPR) anywhere in world. Availibilty of these journals in most of the libraries leads to researchers using these journals only for citations and in turn raising their IFs. If similar reserch is published in JISP and the journal is not available, the chances are, it will not be cited because of its unavailibility.

Self-citations can maipulate jounal IFs. It will be wrong on my part to request you to cite articles from JISP.

Contentious or scientifically poor papers may increase the IF.[5] Scientifically poor articles or controversial papers are remembered more. The 1999 classification of periodontal disease is not only cited for its subject content but also for its controversial content.

The JCR Citation count does not differentiate between original articles, reviews or letters. If a journal tends to publish a large number of letters or reviews, it will show higher IFs.[4]

Larger and older journals generally have higher IFs because of their data base of articles.[4] But smaller journals tend to have higher percentage change in impact factor even if there is a minor change in the number of citations received. A journal that publishes very few articles in a year (denominator in IF equation), gets few extra citations in 2-year time span (the numerator), there will huge change in IF visible. Whereas no such visible change may be obvious for journals who publish large number of articles.

I have been sending the articles back for corrections in the references to all the authors very frequently who submit their manuscripts to JISP. The references should be absolutely correct. This is because any inaccuracies, misprints and irregularities in citations can alter the IF.[4] A quarter of references can get affected by misprints.[3]

Language also creates issues with IFs. Non-English journals are generally cited less than English journals.

IFs are available only for journals covered by the SCI database. The citations in journals not in SCI data base are left out. Citations in books are not included in any IF calculation.[4]

Let us use “THE IMPACT FACTOR” cerebrally, judiciously and after knowing its pros and cons.

Let us not be blinded by the beam of “High Impact”

To be continued…