At Its Core, What Is The Impact Factor Value?
- The impact factor (IF) is utilized as an indicator of the importance of a journal in its discipline.
- It was first developed by Eugene Garfield, the founder of the Institute for Scientific Information.
- Despite the fact that this metric is widely used by institutions and clinicians, people have a common misconception regarding the calculation method of a journal’s impact factor value, its meaning, and how it can be used.
- A journal’s IF is not associated with factors such as the quality of the peer review process and the quality of the journal’s content but is a measure that exhibits the average citation count of articles published in –
- journals,
- books,
- theses,
- project reports,
- conference/seminar proceedings,
- documents published on the Internet,
- notes and any other approved document.
- The impact factor is commonly used to assess the relative importance of a journal in its discipline and to estimate the frequency with which the “average article” of a journal has been cited during a given period.
- Journals that publish more review articles will be recognized as “high impact factors journals“.
- Journals with higher IFs are thought to be more important than those with lower FIs.
- According to Eugene Garfield, the impact factor simply is an indication of the capacity of journals and publishers to attract the best articles available.
- The impact factor can be calculated after the completion of a minimum of three years of publication; for this reason, a journal’s IF value cannot be calculated for new journals.
- A journal with the highest impact factor value is the one that published the most cited articles over a two-year period.
- The IF only applies to journals, not to individual articles or individual scientists, unlike the “H-index”.
- The relative number of citations an individual paper receives is best assessed as “citation impact”.
- In any given year, the IF of a journal is the average number of citations received per article published in this journal during the previous two years.
- IFs are calculated annually by Thomson Scientific for the journals it indexes and are published in Journal Citation Reports.
How Is The IF Value Of A Journal Typically Measured & Calculated
- The calculated and published values are as follows.
- The values are calculated by the Institute for Scientific Information for the journals it indexes; impact factors, and immediacy indices are published yearly in the Journal Citation Reports –
- The Impact Factor Value
- This is a general measure of the impact of the citation; calculated over a two-year period.
- The Immediacy Index Value
- The number of citations a journal’s articles gets in a given year is divided by the number of articles published.
- An immediacy index is a measure of the timeliness and urgency of work published in a scientific journal.
- The Cited Half-Life Value
- The median age of articles that received citations in Journal Citation Reports each year.
- For example, if the half-life of a journal in 2025 will be five, that means the citations from 2021 to 2025 represent half of all citations for that journal in 2025, and the other half of the citations predate 2021.
- The Aggregate Impact Factor Value For A Subject Category
- It is measured by taking into account the number of citations of all the journals in a specific subject and the number of articles of all the journals of the subject category.
These measures apply only to journals, not to individual papers/articles or individual researchers (unlike, for instance, the H-index). The relative number of citations an individual paper/article receives is considered the citation impact.
- The Calculation
- A journal’s impact factor is calculated over a two-year period.
- One can think of this as the average number of citations in a given year to articles in a journal that were published in the previous two years.
- For example, a journal’s 2023 impact factor would be calculated as follows –
- A = number of times articles published in 2021-2022 were cited in journals indexed in 2023
- B = number of “citable items” (usually articles, reviews, reviews, or notes; not editorials and letters to the editor) published in 2021-2022
- Impact factor 2023 = A/B
- (Note that the 2023 impact factor will actually be published in 2024, as it cannot be calculated until all 2023 publications are received)
- An easy way of comprehending this is to imagine that a journal that’s cited once, on average, for every article published, has an impact factor value of 1 in the above expression.
- There are a few nuances to this – ISI excludes certain types of articles (called “front-matter” such as news articles, correspondence, and errata) from the denominator.
- Thomson Scientific doesn’t have a hard and fast rule for what types of articles are considered “citable” and what front-line articles.
- Brand new journals (even renowned Scopus journals publication) that are indexed from their first published issue will receive an impact factor upon the conclusion of two years of indexing; in this case, the citations for the year preceding volume 1 and the number of articles published in the year preceding volume 1 are known null values.
- Journals that are indexed from a volume other than the first volume will not have a published impact factor until three years of complete data are known; directories and other irregular publications sometimes will not publish any articles in a particular year, which will affect the count.
- The impact factor is for a specific period of time; it is possible to estimate the impact factor for any required period for which the website offers instructions.
- Journal Citation Reports include a table of the relative ranking of journals by impact factor in each specific scientific discipline, such as organic chemistry or mechanical engineering.
- The calculation of the IF for the journal in which a person has published articles is a controversial issue.
- Nevertheless, this has already been warned; abuse in the evaluation of individuals because there is great variation from article to article in a single journal, so, in an ideal world, reviewers would read each article and make personal judgments, according to Eugene Garfield.
Research Authors Need To Beware, Impact Factors Aren’t Inffaliable & Can Be Manipulated
- A journal can adopt editorial policies that improve its impact factor.
- These editorial policies cannot be limited to improving the quality of published scientific work.
- Journals can sometimes publish a higher percentage of review articles.
- While many research articles remain uncited after three years, almost all review articles receive at least one citation within three years of publication.
- Therefore, review articles can increase the impact factor of the journal.
- The Thomson Scientific website provides instructions for removing these journals from the calculation.
- For researchers or students with even a slight familiarity with the field, journal reviews will be obvious.
- Journals can change the fraction of “citable items” to raw material in the denominator of the IF equation.
- The types of articles considered “citable” are largely a matter of negotiation between journals and Thomson Scientific.
- As a result of these negotiations, variations in the impact factor of more than 300% were observed.
- For instance, editorials in a journal don’t count as publications.
- Nevertheless, when they cite published articles, often articles from the same journal, these citations increase the citation count of the article.
- This effect is difficult to assess because the distinction between editorial commentary and short original articles is not obvious.
- The “Letters to the editor” sections can belong to either of the classes.
- Numerous methods, not necessarily with nefarious intent, exist for a journal to cite articles in the same journal, which will increase the impact factor of the journal.
- An editor of a journal might encourage authors to cite articles from that journal in the articles they submit.
- The extent to which this practice affects the number of citations and impact factor included in journal data cited by Journal Citation Reports, therefore, needs to be considered.
- Most of these effects are discussed in detail on the site’s help pages, along with ways to correct the numbers for these effects if desired.
- Nevertheless, it is almost universal for articles in a journal to cite primarily its own articles, as they are those of equal merit in the same specialist area.
- If this is done artificially, the effect will become particularly noticeable when –
- journals have low impact factors (in absolute terms) and
- publish a few articles per year.
- Participate in an upcoming conference in 2023 to learn more about all the reasons why a journal’s IF value isn’t necessarily a mark of its quality.
How Not To Use The Impact Factor Value Of A Journal
- The impact factor is often misused in the prediction of the importance of an individual post based on where it was posted.
- This does not work well because a small number of publications are cited much more than the majority – for instance, around the overwhelming majority of a highly reputable journal’s impact factor could be based entirely on only a quarter of its publications, and therefore the importance of any publication will be different and on average lower than the total number.
- The impact factor, however, averages all articles and therefore underestimates the citations of the top cited while overstating the number of citations of the average publication.
- Academic reviewers involved in program evaluations, especially those at doctoral awarding institutions, often look to ISI’s proprietary IF list of the top most academic journals 2023 to determine scholarly output.
- This creates a bias that automatically underestimates certain types of research and distorts the total contribution of each faculty member.
- The absolute value of an impact factor has no meaning in itself.
- A journal with an IF of two would not be very impressive in a field such as Particle Physics, whereas it would be in Biomedical Engineering.
- However, such values are sometimes announced by scientific publishers.
- A comparison of impact factors between different domains is not valid.
- Yet these comparisons have been widely employed for the evaluation not only of journals but also of scientists and academic departments.
- It’s not right to say, for instance, that a department whose publications have an average IF of less than two is of a low level.
- This wouldn’t make sense for mechanical engineering, where only two review journals achieve such value.
- Outside of science, impact factors are relevant for fields that have a publication pattern similar to science (such as economics), where research publications are almost always journal articles that cite other journals’ research articles.
- They are irrelevant to literature, where the most important publications are books citing other books.
- Therefore, Thomson Scientific does not publish JCRs for the humanities.
- Even if applied in this way in practice, impact factors cannot be properly considered by libraries in journal selection.
- The journal’s local usefulness is at least as important as is whether or not a faculty member at an institution is the journal’s editor or member of its editorial board.
- Although the impact factor was originally conceived as an objective measure of a journal’s reputation (Garfield), it is now increasingly applied to measure the productivity of scientists.
- It is usually used to analyze the impact factors of the journals in which the researcher’s articles have been published.
- This has obvious allure for an academic administrator unfamiliar with the subject or the journals.
- The absolute number of research scientists, the average number of authors on each article, and the nature of the results in different fields of research, as well as variations in citation habits between different disciplines, in particular the number of citations in each article, combine to impact factors between different groups of scientists immeasurably.
- Generally, for instance, medical journals have higher impact factors than mathematical journals and engineering journals.
- This limitation is accepted by the publishers; they were never claimed to be useful across domains – such use is an indication of misunderstanding.
- The HEFCE (Higher Education Funding Council for England) has been urged by the UK Parliament’s Science and Technology Committee to remind Research Assessment Exercise (RAE) panels that they are required to evaluate the content quality of individual articles, not the reputability of the journal in which they are published.
- The number of article citations in a particular journal doesn’t really directly indicate the true quality of a scientific journal, much less the scientific merit of the articles the journal contains.
- It is also a reflection, at least in part, of the intensity of publication or citation in that field, the current popularity of that particular subject, as well as the availability of particular journals.
- Low circulation journals, regardless of the scientific merit of their content, will never achieve high impact factors in absolute terms, but if all the journals on a specific topic are low circulation, as in some fields of botany and zoology, the standing relationship is significant.
- Owing to the fact that defining the quality of an academic publication is challenging, involving unquantifiable factors, such as the impact on the next generation of researchers, assigning this value to a specific numerical measure cannot tell the whole story.
- By simply counting the frequency of citations per article and ignoring the prestige of the citing journals, the impact factor simply becomes a measure of popularity, not prestige.
The Actual Significance Of The Impact Factor Value Of Journals
- It is important to remember that although impact factors tend to correlate with the reliability or prestige of the journal, the metric is not in itself an indicator of the quality of the journal.
- Thinking back to the calculation discussed earlier, the impact factor is simply the ratio of citations to recent citable articles published.
- Many scholars and institutions erroneously refer to impact factors as a measure of journal quality when it is instead a measure of impact on the academic community of interest.
- In reality, the absolute value of the impact factor value of a journal doesn’t mean much; these values must be interpreted in the appropriate context.
- Citation habits and frequency of publication vary considerably from one field of research to another.
- Therefore, impact factors shouldn’t be made use of to compare journals across disciplines.
- For instance, the frequency of citations and publications is much lower in mathematics and physics than in medicine, so medical journals will generally have higher impact factors.
- Review articles, in particular, typically are read and cited more frequently; therefore, journals that publish review articles may inflate impact factor scores.
- Each year, publishers are under pressure to increase journal impact factors. There have been instances of journal editors unethically manipulating impact factors to improve ratings for secondary gain.
- Editors can achieve this by rejecting manuscripts if they are unlikely to be highly cited, or even some have gone so far as to reject heavy-handed manuscripts and authors in order to cite more papers/articles from their journal exclusively in order to be accepted.
Narrow-focus journals that cater to a more niche community like Astroparticle Physics will inevitably have a lower impact factor than those that reach a broader reader base like the Journal of Astronomy.
- The types of articles and the size of the target audience for a journal play an important role in the final value of the impact factor.
- Although journal impact factors can be a useful tool for evaluating and comparing journals in a specific field, the decision to submit your manuscript to a journal should not be based entirely on their impact factor.
- Know your target audience and do some research to decide correctly which journal would be the best suited for your work to be published in, and don’t get too distracted with where your publication will fall on the “prestige” ranking.
- For most students and research professionals, the objective would be to write a paper with a high impact factor.
- However, you usually have to walk before you run.
- Therefore, working with an assistant and publishing journal articles, book chapters, and case reports is a great way to learn editing basics.
- At this level, any posting looks impressive on your resume and gives residency and fellowship program directors an appreciation of your ability to write well and your work ethic.
- As your experience increases, moving on to research papers in high-impact journals will be an easier “next step” if you have gained experience.
Crucial Facts About The Impact Factor That All Research Authors Should Be Aware Of
- It is crucial for market research for publishers and others.
- It is an important tool for librarians, researchers, and librarians.
- It is also a vital tool for the researcher to select a reputable journal and publish it in old and reputable journals.
- The impact factor can be made use of to provide a rough approximation of a journal’s prestige.
- It is also a tool for judicious use and careful citation of data in journals.
- In general, authors should bear in mind that
- The impact factor can be calculated after completing the minimum three years of publication.
- The log impact factor will only be a quotient factor and will not be a quality factor.
- The impact factor of the journal will not be related to the quality of content and the quality of peer review.
- Journals that publish more review articles will get the highest impact factors.
- The impact factor strongly depends on the discipline.
- The impact factor couldn’t be reproduced in an independent audit.
- The impact factor has to do with the average number of citations per article.
- Citation counting can be independent of the actual “impact” of the work among researchers and scientific communities.
- Self-citations and deliberate addition of the same journal article with favorable editorial policies may journals or publishers not be taken into account for the evaluation of the impact factor.
- The citation count may be applied incorrectly to rate the importance of an individual post or to rate an individual researcher.
- A title change has an impact on the impact factor for two years after a change has been made. Old and new titles typically aren’t unified unless the titles are in the same place in alphabetical order