The 5-year journal Impact Factor is the average number of times articles from the journal published in the past five years have been cited in the JCR year. It is caclulated by dividing the number of citations in the JCR year by the total number of articles published in the five previous years.
The 5-year Impact Factor is available only in JCR 2007 and subsequent years.
For comparing journals specializing in cutting-edge research, the immediacy index can provide a useful perspective.
The Immediacy Index is the average number of times an article is cited in the year it is published.
The Immediacy Index is calculated by dividing the number of citations to articles published in a given year by the number of articles published in that year.
You should not depend solely on citation data when evaluating journals, but it can be used to help support and inform qualitative, peer review. Many factors can influence citation rates such as language, journal history, publication schedule, and subject specialty and scope.
Other factors which can affect a journal's ranking or metrics include:
Many of the journals in Web of Science and Scopus are English-language from North America, Western Europe and Australia. Irish journals in many research areas can be underrepresented.
Review journals and original research journals are treated the same even though the citation patterns of these types of articles differ.
The journal Impact Factor is the average number of times articles from the journal published in the past two years have been cited in the Journal Citation Reports (JCR) year.
The Impact Factor is calculated by dividing the number of citations in the JCR year by the total number of articles published in the two previous years. An Impact Factor of 1.0 means that, on average, the articles published one or two year ago have been cited one time. An Impact Factor of 2.5 means that, on average, the articles published one or two year ago have been cited two and a half times. Citing articles may be from the same journal; most citing articles are from different journals.
The journal Impact Factor was developed by Eugene Garfield at the Institute for Scientific Information (ISI), and is now owned by Clarivate Analytics.
Impact Factor uses Web of Science (Clarivate Analytics) citation data.
Calculation of the 2014 Journal Impact Factor for the Journal of Information Technology
Initiated in 2012 the American Society for Cell Biology and a group of editors and publishers of scholarly journals drafted and circulated a declaration that recognises the need to improve the ways in which the outputs of scientific research are evaluated.
"The Journal Impact Factor, as calculated by Thomson Reuters, was originally created as a tool to help librarians identify journals to purchase, not as a measure of the scientific quality of research in an article. With that in mind, it is critical to understand that the Journal Impact Factor has a number of well-documented deficiencies as a tool for research assessment. These limitations include:
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