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82-514: The Leiden Ranking ranks universities worldwide by number of academic publications according to the volume and citation impact of the publications at those institutions. The rankings take into account differences in language, discipline and institutional size. Multiple ranking lists are released according to various bibliometric normalization and impact indicators, including the number of publications, citations per publication, and field-normalized impact per publication. In addition to citation impact,

164-518: A different perspective on research impact, concentrating more on immediate social impact in and outside academia. Fake impact factors or bogus impact factors are produced by certain companies or individuals. According to an article published in the Electronic Physician , these include Global Impact Factor, Citefactor, and Universal Impact Factor. Jeffrey Beall maintained a list of such misleading metrics. Another deceitful practice

246-642: A feature of the economy is picked as an indicator of the economy, then it inexorably ceases to function as that indicator because people start to game it." Open access publications are accessible without cost to readers, hence they would be expected to be cited more frequently. Some experimental and observational studies have found that articles published in open access journals do not receive more citations, on average, than those published in subscription journals; other studies have found that they do. The evidence that author-self-archived ("green") open access articles are cited more than non open access articles

328-686: A good indicator of highly cited articles, leading the author to propose a "Twimpact factor", which is the number of Tweets it receives in the first seven days of publication, as well as a Twindex, which is the rank percentile of an article's Twimpact factor. In response to growing concerns over the inappropriate use of journal impact factors in evaluating scientific outputs and scientists themselves, Université de Montréal , Imperial College London , PLOS , eLife , EMBO Journal , The Royal Society , Nature and Science proposed citation distributions metrics as alternative to impact factors. An important recent development in research on citation impact

410-433: A good technique for scientific evaluation. Experience has shown that in each specialty the best journals are those in which it is most difficult to have an article accepted, and these are the journals that have a high impact factor. Most of these journals existed long before the impact factor was devised. The use of impact factor as a measure of quality is widespread because it fits well with the opinion we have in each field of

492-464: A higher aggregation level, rather than at the level of individual publications, gives more weight to older publications, particularly reviews, and to publications in fields where citation levels are traditionally higher. Citation impact Citation impact or citation rate is a measure of how many times an academic journal article or book or author is cited by other articles, books or authors. Citation counts are interpreted as measures of

574-519: A larger percentage of review articles which generally are cited more than research reports. Research undertaken in 2020 on dentistry journals concluded that the publication of "systematic reviews have significant effect on the Journal Impact Factor ... while papers publishing clinical trials bear no influence on this factor. Greater yearly average of published papers ... means a higher impact factor." Journals may also attempt to limit

656-521: A mixture of metrics on their website; the PLOS series of journals does not display the impact factor. Microsoft Academic took a similar view, stating that h-index, EI/SCI and journal impact factors are not shown because "the research literature has provided abundant evidence that these metrics are at best a rough approximation of research impact and scholarly influence." In 2021, Utrecht University promised to abandon all quantitative bibliometrics, including

738-429: A narrow focus on publishing in top-tier journals, potentially compromising the diversity of research topics and methodologies. Further criticisms argue that emphasis on impact factor results from the negative influence of neoliberal politics on academia. Some of these arguments demand not just replacement of the impact factor with more sophisticated metrics but also discussion on the social value of research assessment and

820-1414: A new corporation, Clarivate, which is now the publisher of the JCR. In any given year, the two-year journal impact factor is the ratio between the number of citations received in that year for publications in that journal that were published in the two preceding years and the total number of "citable items" published in that journal during the two preceding years: IF y = Citations y Publications y − 1 + Publications y − 2 . {\displaystyle {\text{IF}}_{y}={\frac {{\text{Citations}}_{y}}{{\text{Publications}}_{y-1}+{\text{Publications}}_{y-2}}}.} For example, Nature had an impact factor of 41.577 in 2017: IF 2017 = Citations 2017 Publications 2016 + Publications 2015 = 74090 880 + 902 = 41.577. {\displaystyle {\text{IF}}_{2017}={\frac {{\text{Citations}}_{2017}}{{\text{Publications}}_{2016}+{\text{Publications}}_{2015}}}={\frac {74090}{880+902}}=41.577.} This means that, on average, its papers published in 2015 and 2016 received roughly 42 citations each in 2017. 2017 impact factors are reported in 2018; they cannot be calculated until all of

902-431: A protest against the "absurd scientific situation in some countries" related to use of the impact factor. 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 and 2009 Journal Citation Reports . Coercive citation is a practice in which an editor forces an author to add extraneous citations to an article before

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984-510: A scholar's impact relies on usage data, such as number of downloads from publishers and analyzing citation performance, often at article level . As early as 2004, the BMJ published the number of views for its articles, which was found to be somewhat correlated to citations. In 2008 the Journal of Medical Internet Research began publishing views and Tweets . These "tweetations" proved to be

1066-522: A scientific paper without seeing the primary data, so should they not rely on Thomson Scientific's impact factor, which is based on hidden data". However, a 2019 article demonstrated that "with access to the data and careful cleaning, the JIF can be reproduced", although this required much labour to achieve. A 2020 research paper went further. It indicated that by querying open access or partly open-access databases, like Google Scholar, ResearchGate, and Scopus, it

1148-660: A set of English-language journals with international scope and a "sufficiently large" number of references in the Web of Science database. According to the Netherlands Centre for Science and Technology Studies, the crown indicator is Indicator 4 (PP top 10%), and is the only one presented in university rankings by the Swiss State Secretariat for Education, Research and Innovation website (UniversityRankings.ch). As of 2023, Chinese universities dominate

1230-491: A small number of very highly cited papers. For instance, most papers in Nature (impact factor 38.1, 2016) were only cited 10 or 20 times during the reference year (see figure). Journals with a lower impact (e.g. PLOS ONE , impact factor 3.1) publish many papers that are cited 0 to 5 times but few highly cited articles. Journal-level metrics are often misinterpreted as a measure for journal quality or article quality. However,

1312-685: A statistical method to evaluate the universality of citation impact metrics, i.e., their capability to compare impact fairly across fields. Their analysis identifies universal impact metrics, such as the field-normalized h-index. Research suggests the impact of an article can be, partly, explained by superficial factors and not only by the scientific merits of an article. Field-dependent factors are usually listed as an issue to be tackled not only when comparison across disciplines are made, but also when different fields of research of one discipline are being compared. For instance in Medicine among other factors

1394-458: Is "a wide variation [of citations] from article to article within a single journal". Despite this warning, the use of the JIF has evolved, playing a key role in the process of assessing individual researchers, their job applications and their funding proposals. In 2005, The Journal of Cell Biology noted that: Impact factor data ... have a strong influence on the scientific community, affecting decisions on where to publish, whom to promote or hire,

1476-614: Is accessible to all registered users, who can independently verify the number of citable items for a given journal. In contrast, the number of citations is extracted not from the WoS database, but from a dedicated JCR database, which is not accessible to general readers. Hence, the commonly used "JCR Impact Factor" is a proprietary value, which is defined and calculated by ISI and can not be verified by external users. New journals, which are indexed from their first published issue, will receive an impact factor after two years of indexing; in this case,

1558-453: Is frequently used as a proxy for the relative importance of a journal within its field; journals with higher impact factor values are given the status of being more important, or carry more prestige in their respective fields, than those with lower values. While frequently used by universities and funding bodies to decide on promotion and research proposals, it has been criticised for distorting good scientific practices. The impact factor

1640-408: Is possible to calculate approximate impact factors without the need to purchase Web of Science / JCR. Just as the impact factor has attracted criticism for various immediate problems associated with its application, so has there also been criticism that its application undermines the broader process of science. Research has indicated that bibliometrics figures, particularly the impact factor, decrease

1722-460: Is somewhat stronger than the evidence that ("gold") open access journals are cited more than non open access journals. Two reasons for this are that many of the top-cited journals today are still only hybrid open access (author has the option to pay for gold) and many pure author-pays open access journals today are either of low quality or downright fraudulent "predatory journals," preying on authors' eagerness to publish-or-perish, thereby lowering

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1804-399: Is the discovery of universality , or citation impact patterns that hold across different disciplines in the sciences, social sciences, and humanities. For example, it has been shown that the number of citations received by a publication, once properly rescaled by its average across articles published in the same discipline and in the same year, follows a universal log-normal distribution that

1886-453: Is the same in every discipline. This finding has suggested a universal citation impact measure that extends the h-index by properly rescaling citation counts and resorting publications, however the computation of such a universal measure requires the collection of extensive citation data and statistics for every discipline and year. Social crowdsourcing tools such as Scholarometer have been proposed to address this need. Kaur et al. proposed

1968-771: The San Francisco Declaration on Research Assessment (DORA). Released in May 2013, DORA has garnered support from thousands of individuals and hundreds of institutions, including in March 2015 the League of European Research Universities (a consortium of 21 of the most renowned research universities in Europe), who have endorsed the document on the DORA website. Publishers, even those with high impact factors, also recognised

2050-612: The University of Oxford , the University of Cambridge , and other British universities score much lower than in other university rankings, such as the Times Higher Education World University Rankings and QS World University Rankings , which are based in part on reputational surveys among academics. When measuring by collaboration with other universities (the proportion of number of publications co-authored with other institutions),

2132-402: The citescore . It is used by academic institutions in decisions about academic tenure , promotion and hiring, and hence also used by authors in deciding which journal to publish in. Citation-like measures are also used in other fields that do ranking , such as Google 's PageRank algorithm, software metrics , college and university rankings , and business performance indicators . One of

2214-519: The h-index and the impact factor". The UK's Research Assessment Exercise for 2014 also banned the journal impact factor although evidence suggested that this ban was often ignored. In response to growing concerns over the inappropriate use of journal impact factors in evaluating scientific outputs and scientists themselves, the American Society for Cell Biology together with a group of editors and publishers of scholarly journals created

2296-457: The h-index . Each measure has advantages and disadvantages, spanning from bias to discipline-dependence and limitations of the citation data source. Counting the number of citations per paper is also employed to identify the authors of citation classics. Citations are distributed highly unequally among researchers. In a study based on the Web of Science database across 118 scientific disciplines,

2378-468: The median of these data. There is also a more general debate on the validity of the impact factor as a measure of journal importance and the effect of policies that editors may adopt to boost their impact factor (perhaps to the detriment of readers and writers). Other criticism focuses on the effect of the impact factor on behavior of scholars, editors and other stakeholders. Criticism of impact factors also extends to its impact on researcher behavior. While

2460-526: The 2017 publications have been processed by the indexing agency. The value of impact factor depends on how to define "citations" and "publications"; the latter are often referred to as "citable items". In current practice, both "citations" and "publications" are defined exclusively by ISI as follows. "Publications" are items that are classed as "article", "review" or "proceedings paper" in the Web of Science (WoS) database; other items like editorials, corrections, notes, retractions and discussions are excluded. WoS

2542-512: The 4 million included in this study constitute a tiny fraction. The simplest journal-level metric is the journal impact factor , the average number of citations that articles published by a journal in the previous two years have received in the current year, as calculated by Clarivate . Other companies report similar metrics, such as the CiteScore , based on Scopus . However, very high journal impact factor or CiteScore are often based on

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2624-641: The Conduct of Science issued a "statement on publication practices and indices and the role of peer review in research assessment", suggesting many possible solutions—e.g., considering a limit number of publications per year to be taken into consideration for each scientist, or even penalising scientists for an excessive number of publications per year—e.g., more than 20. In February 2010, the Deutsche Forschungsgemeinschaft (German Research Foundation) published new guidelines to reduce

2706-411: The JIF as part of such review, promotion, and tenure processes. And a 2017 study of how researchers in the life sciences behave concluded that "everyday decision-making practices as highly governed by pressures to publish in high-impact journals". The deeply embedded nature of such indicators not only effect research assessment, but the more fundamental issue of what research is actually undertaken: "Given

2788-461: The JIF is still useful, and that omitting it "will lead to randomness and a compromising of scientific quality". Some related metrics, also calculated and published by the same organization, include: A given journal may attain a different quartile or percentile in different categories. As with the impact factor, there are some nuances to this: for example, Clarivate excludes certain article types (such as news items, correspondence, and errata) from

2870-497: The JIF state that use of the arithmetic mean in its calculation is problematic because the pattern of citation distribution is skewed and citation distributions metrics have been proposed as an alternative to impact factors. However, there have also been pleas to take a more nuanced approach to judging the distribution skewness of the impact factor. Ludo Waltman and Vincent Antonio Traag, in their 2021 paper, ran numerous simulations and concluded that "statistical objections against

2952-544: The JIF to cultivate a competition regime in academia has been shown to have deleterious effects on research quality. A number of regional and international initiatives are now providing and suggesting alternative research assessment systems, including key documents such as the Leiden Manifesto and the San Francisco Declaration on Research Assessment (DORA). Plan S calls for a broader adoption and implementation of such initiatives alongside fundamental changes in

3034-508: The Leiden Ranking also ranks universities by scientific collaboration, including collaboration with other institutions and collaboration with an industry partner. The first edition of the Leiden Ranking was produced in 2007. The 2014 rankings include 750 universities worldwide, which were selected based on the number of articles and reviews published by authors affiliated with those institutions in 2009–2012 in so-called "core" journals,

3116-423: The average citation counts of open access journals. Journal impact factor The impact factor ( IF ) or journal impact factor ( JIF ) of an academic journal is a scientometric index calculated by Clarivate that reflects the yearly mean number of citations of articles published in the last two years in a given journal, as indexed by Clarivate's Web of Science . As a journal-level metric , it

3198-424: The best journals in our specialty....In conclusion, prestigious journals publish papers of high level. Therefore, their impact factor is high, and not the contrary. As impact factors are a journal-level metric, rather than an article- or individual-level metric, this use is controversial. Eugene Garfield, the inventor of the JIF agreed with Hoeffel, but warned about the "misuse in evaluating individuals" because there

3280-536: The calendar year. This gives those papers more time to gather citations. 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. Beyond editorial policies that may skew the impact factor, journals can take overt steps to game the system . For example, in 2007, the specialist journal Folia Phoniatrica et Logopaedica , with an impact factor of 0.66, published an editorial that cited all its articles from 2005 to 2006 in

3362-808: The case of the article "A short history of SHELX", which included this sentence: "This paper could serve as a general literature citation when one or more of the open-source SHELX programs (and the Bruker AXS version SHELXTL) are employed in the course of a crystal-structure determination". This article received more than 6,600 citations. As a consequence, the impact factor of the journal Acta Crystallographica Section A rose from 2.051 in 2008 to 49.926 in 2009, more than Nature (at 31.434) and Science (at 28.103). The second-most cited article in Acta Crystallographica Section ;A in 2008 had only 28 citations. Critics of

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3444-420: The citations that might be obtained at any time of the lifetime of a corpus of publications. Some researchers also propose that the journal citation rate on Misplaced Pages, next to the traditional citation index, "may be a good indicator of the work's impact in the field of psychology." According to Mario Biagioli: "All metrics of scientific evaluation are bound to be abused. Goodhart's law [...] states that when

3526-546: 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. Occasionally, Journal Citation Reports assigns an impact factor to new journals with less than two years of indexing, based on partial citation data. The calculation always uses two complete and known years of item counts, but for new titles one of

3608-509: The current ways of evaluation and valuing research, risky, lengthy, and unorthodox project rarely take center stage." Numerous critiques have been made regarding the use of impact factors, both in terms of its statistical validity and also of its implications for how science is carried out and assessed. A 2007 study noted that the most fundamental flaw is that impact factors present the mean of data that are not normally distributed , and suggested that it would be more appropriate to present

3690-696: The denominator. Additional journal-level metrics are available from other organizations. For example, CiteScore is a metric for serial titles in Scopus launched in December 2016 by Elsevier . While these metrics apply only to journals, there are also author-level metrics , such as the h-index , that apply to individual researchers. In addition, article-level metrics measure impact at an article level instead of journal level. Other more general alternative metrics, or " altmetrics ", that include article views, downloads, or mentions in social media , offer

3772-552: The denominator. One notorious example of this occurred in 1988 when it was decided that meeting abstracts published in FASEB Journal would no longer be included in the denominator. The journal's impact factor jumped from 0.24 in 1988 to 18.3 in 1989. Publishers routinely discuss with Clarivate how to improve the "accuracy" of their journals' impact factor and therefore get higher scores. Such discussions routinely produce "negotiated values" which result in dramatic changes in

3854-400: The emphasis on high-impact journals may lead to strategic publishing practices that prioritize journal prestige over the quality and relevance of research, it's important to acknowledge the "privilege paradox". Younger researchers, particularly those from under-represented regions, often lack the established reputation or networks to secure recognition outside of these metrics. This can lead to

3936-424: The flaws. Nature magazine criticised the over-reliance on JIF, pointing not just to its statistical flaws but to negative effects on science: "The resulting pressures and disappointments are nothing but demoralizing, and in badly run labs can encourage sloppy research that, for example, fails to test assumptions thoroughly or to take all the data into account before submitting big claims." Various publishers now use

4018-464: The following indicators: In a 2010 article, Loet Leydesdorff criticized the method used by the Leiden Ranking to normalize citation impact by subject field. The mean normalized citation score (MNCS) indicator is based on the ISI subject category classification used in Web of Science, which was "not designed for the scientometric evaluation, but for the purpose of information retrieval". Also, normalizing at

4100-457: The growing precariousness of scientific careers in higher education. It has been stated that impact factors in particular and citation analysis in general are affected by field-dependent factors which invalidate comparisons not only across disciplines but even within different fields of research of one discipline. The percentage of total citations occurring in the first two years after publication also varies highly among disciplines from 1–3% in

4182-531: The impact factor. The university stated that "it has become a very sick model that goes beyond what is really relevant for science and putting science forward". This followed a 2018 decision by the main Dutch funding body for research, NWO , to remove all references to journal impact factors and the h-index in all call texts and application forms. Utrecht's decision met with some resistance. An open letter signed by over 150 Dutch academics argued that, while imperfect,

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4264-426: The impact or influence of academic work and have given rise to the field of bibliometrics or scientometrics , specializing in the study of patterns of academic impact through citation analysis . The importance of journals can be measured by the average citation rate, the ratio of number of citations to number articles published within a given time period and in a given index, such as the journal impact factor or

4346-635: The institutional level. It thus has significant impact on steering research practices and behaviours. By 2010, national and international research funding institutions were already starting to point out that numerical indicators such as the JIF should not be considered as a measure of quality. In fact, research was indicating that the JIF is a highly manipulated metric, and the justification for its continued widespread use beyond its original narrow purpose seems due to its simplicity (easily calculable and comparable number), rather than any actual relationship to research quality. Empirical evidence shows that

4428-623: The journal impact factor. 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". In July 2008, the International Council for Science Committee on Freedom and Responsibility in

4510-418: The journal will agree to publish it, in order to inflate the journal's impact factor. A survey published in 2012 indicates that coercive citation has been experienced by one in five researchers working in economics, sociology, psychology, and multiple business disciplines, and it is more common in business and in journals with a lower impact factor. Editors of leading business journals banded together to disavow

4592-450: The known counts is zero. Annuals and other irregular publications 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. For example, the JCR also includes a five-year impact factor , which is calculated by dividing the number of citations to the journal in a given year by the number of articles published in that journal in

4674-409: The marginalization of research in vernacular languages and on locally relevant topics and inducement to unethical authorship and citation practices. More generally, the impact factors fosters a reputation economy, where scientific success is based on publishing in prestigious journals ahead of actual research qualities such as rigorous methods, replicability and social impact. Using journal prestige and

4756-647: The mathematical and physical sciences to 5–8% in the biological sciences. Thus impact factors cannot be used to compare journals across disciplines. Impact factors are sometimes used to evaluate not only the journals but the papers therein, thereby devaluing papers in certain subjects. In 2004, 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

4838-509: The misuse of the JIF—and journal ranking metrics in general—has a number of negative consequences for the scholarly communication system. These include gaps between the reach of a journal and the quality of its individual papers and insufficient coverage of social sciences and humanities as well as research outputs from across Latin America, Africa, and South-East Asia. Additional drawbacks include

4920-591: The most basic citation metrics is how often an article was cited in other articles, books, or other sources (such as theses). Citation rates are heavily dependent on the discipline and the number of people working in that area. For instance, many more scientists work in neuroscience than in mathematics, and neuroscientists publish more papers than mathematicians, hence neuroscience papers are much more often cited than papers in mathematics. Similarly, review papers are more often cited than regular research papers because they summarize results from many papers. This may also be

5002-405: The nature of citation analysis research, allowing millions of citations to be analyzed for large scale patterns and knowledge discovery. The first example of automated citation indexing was CiteSeer , later to be followed by Google Scholar . More recently, advanced models for a dynamic analysis of citation aging have been proposed. The latter model is even used as a predictive tool for determining

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5084-599: The number of "citable items"—i.e., the denominator of the impact factor equation—either by declining to publish articles that are unlikely to be cited (such as case reports in medical journals) or by altering articles (e.g., by not allowing an abstract or bibliography in hopes that Journal Citation Reports will not deem it a "citable item"). As a result of negotiations over whether items are "citable", impact factor variations of more than 300% have been observed. Items considered to be uncitable—and thus are not incorporated in impact factor calculations—can, if cited, still enter into

5166-476: The number of authors, the number of references, the article length, and the presence of a colon in the title influence the impact. Whilst in Sociology the number of references, the article length, and title length are among the factors. Also it is found that scholars engage in ethically questionable behavior in order to inflate the number of citations articles receive. Automated citation indexing has changed

5248-427: The number of publications that could be submitted when applying for funding: "The focus has not been on what research someone has done but rather how many papers have been published and where." They noted that for decisions concerning "performance-based funding allocations, postdoctoral qualifications, appointments, or reviewing funding proposals, [where] increasing importance has been given to numerical indicators such as

5330-444: The numerator part of the equation despite the ease with which such citations could be excluded. This effect is hard to evaluate, for the distinction between editorial comment and short original articles is not always obvious. For example, letters to the editor may be part of either class. Another less insidious tactic journals employ is to publish a large portion of its papers, or at least the papers expected to be highly cited, early in

5412-428: The observed scores for dozens of journals, sometimes after unrelated events like the purchase by one of the larger publishers. Because citation counts have highly skewed distributions , the mean number of citations is potentially misleading if used to gauge the typical impact of articles in the journal rather than the overall impact of the journal itself. For example, about 90% of Nature ' s 2004 impact factor

5494-510: The practice. However, cases of coercive citation have occasionally been reported for other disciplines. The journal impact factor was originally designed by Eugene Garfield as a metric to help librarians make decisions about which journals were worth indexing, as the JIF aggregates the number of citations to articles published in each journal. Since then, the JIF has become associated as a mark of journal "quality", and gained widespread use for evaluation of research and researchers instead, even at

5576-448: The previous five years. While originally invented as a tool to help university librarians to decide which journals to purchase, the impact factor soon became used as a measure for judging academic success. This use of impact factors was summarised by Hoeffel in 1998: Impact Factor is not a perfect tool to measure the quality of articles but there is nothing better and it has the advantage of already being in existence and is, therefore,

5658-424: The process of publication and science is slowed down – authors automatically try and publish with the journals with the highest impact factor – "as editors and reviewers are tasked with reviewing papers that are not submitted to the most appropriate venues". Given the growing criticism and its widespread usage as a means of research assessment, organisations and institutions have begun to take steps to move away from

5740-401: The quality of peer review an article receives, cause a reluctance to share data, decrease the quality of articles, and a reduce the scope in of publishable research. "For many researchers the only research questions and projects that appear viable are those that can meet the demand of scoring well in terms of metric performance indicators – and chiefly the journal impact factor.". Furthermore,

5822-515: The quality of the content of individual articles, not the reputation of the journal in which they are published. Other studies have repeatedly stated that impact factor is a metric for journals and should not be used to assess individual researchers or institutions. Because impact factor is commonly accepted as a proxy for research quality, some journals adopt editorial policies and practices, some acceptable and some of dubious purpose, to increase its impact factor. For example, journals may publish

5904-453: The rankings, with 16 out of the top 25 universities ranked being in China., while in previous years, the top was heavily dominated by American universities. In the 2014 rankings, Rockefeller University was first by citation impact, as measured by both mean citation score and mean normalized citation score, as well as by the proportion of papers belonging to the top 10% in their field. Notably,

5986-885: The reason why papers with shorter titles get more citations, given that they are usually covering a broader area. The most-cited paper in history is a paper by Oliver Lowry describing an assay to measure the concentration of proteins . By 2014 it had accumulated more than 305,000 citations. The 10 most cited papers all had more than 40,000 citations. To reach the top-100 papers required 12,119 citations by 2014. Of Thomson Reuter's Web of Science database with more than 58 million items only 14,499 papers (~0.026%) had more than 1,000 citations in 2014. Total citations, or average citation count per article, can be reported for an individual author or researcher. Many other measures have been proposed, beyond simple citation counts, to better quantify an individual scholar's citation impact. The best-known author-level measures include total citations and

6068-563: The scholarly communication system. As appropriate measures of quality for authors and research, concepts of research excellence should be remodelled around transparent workflows and accessible research results. JIFs are still regularly used to evaluate research in many countries, which is a problem since a number of issues remain around the opacity of the metric and the fact that it is often negotiated by publishers. Results of an impact factor can change dramatically depending on which items are considered as "citable" and therefore included in

6150-516: The success of grant applications, and even salary bonuses. More targeted research has begun to provide firm evidence of how deeply the impact factor is embedded within formal and informal research assessment processes. A review in 2019 studied how often the JIF featured in documents related to the review, promotion, and tenure of scientists in US and Canadian universities. It concluded that 40% of universities focused on academic research specifically mentioned

6232-546: The top 1% most-cited authors accounted for 21% of all citations. Between 2000 and 2015, the proportion of citations that went to this elite group grew from 14% to 21%. The highest concentrations of 'citation elite' researchers were in the Netherlands , the United Kingdom , Switzerland and Belgium . 70% of the authors in the Web of Science database have fewer than 5 publications, so that the most-cited authors among

6314-526: The top three spots were occupied by National Yang-Ming University and two other institutions from Taiwan in 2014, followed by universities from France , the United Kingdom and a number of other European countries. King Abdulaziz University and King Saud University in Saudi Arabia led the list in 2014 when measured by international collaboration. The Leiden Ranking ranks universities by

6396-431: The use of non-article-level metrics to determine the impact of a single article is statistically invalid. Moreover, studies of methodological quality and reliability have found that "reliability of published research works in several fields may be decreasing with increasing journal rank", contrary to widespread expectations. Citation distribution is skewed for journals because a very small number of articles are driving

6478-459: The use of the IF at the level of individual articles are not convincing", and that "the IF may be a more accurate indicator of the value of an article than the number of citations of the article". While the underlying mathematical model is publicly known, the dataset which is used to calculate the JIF is not publicly available. This prompted criticism: "Just as scientists would not accept the findings in

6560-548: The vast majority of citations; therefore, some journals have stopped publicizing their impact factor, e.g. the journals of the American Society for Microbiology . Citation counts follow mostly a lognormal distribution , except for the long tail , which is better fit by a power law . Other journal-level metrics include the Eigenfactor , and the SCImago Journal Rank . An alternative approach to measure

6642-444: Was based on only a quarter of its publications. Thus the actual number of citations for a single article in the journal is in most cases much lower than the mean number of citations across articles. Furthermore, the strength of the relationship between impact factors of journals and the citation rates of the papers therein has been steadily decreasing since articles began to be available digitally. The effect of outliers can be seen in

6724-653: Was devised by Eugene Garfield , the founder of the Institute for Scientific Information (ISI) in Philadelphia. Impact factors began to be calculated yearly starting from 1975 for journals listed in the Journal Citation Reports (JCR). ISI was acquired by Thomson Scientific & Healthcare in 1992, and became known as Thomson ISI. In 2018, Thomson-Reuters spun off and sold ISI to Onex Corporation and Baring Private Equity Asia . They founded

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