The InCites explorer includes Journal Citation Reports journal indicators and links to JCR Journal Profiles within the results table. For analysis focused on research producers, these indicators identify the share of work published in top journals, enhancing promotion or enabling strategies for improved standing within the community and among competitors. Publishers can now leverage the improved features of InCites Benchmarking to track performance of journals, identify significant contributors, and benchmark against peers.
- For all indicators in InCites in non-, the time period will dictate the JCR year of the indicator displayed; for example, a time period filter of 1980-2017 will display the 2017 JCR indicator; a time period filter of 1980-2012 will display the 2012 JCR indicator
- For all indicators in InCites in Journal entity, only the latest JCR data is displayed
- All indicators are covered from 1997-present
Documents published in a journal found in Journal Citation Reports in a given year.
The number of documents that appear in a journal in a particular Journal Impact Factor Quartile in a given year. For instance, a value of 100 indicates 100 documents in the set were published in journals of the specified Journal Impact Factor Quartile in that year.
InCites uses the best quartile for journals that appear in multiple Web of Science Research Areas. When a research area is specified, the quartile for that particular journal and research area is used.
Percentage of documents that appear in a journal in a particular Journal Impact Factor Quartile in a given year. For example, if a value displays 10%, it indicates that 10% of the documents in the set were published in journals of the specified Journal Impact Factor Quartile in that year.
% of documents in Q1 Journals = (Count of Documents in Q1 Journals) / (Count of Documents in JIF Journals)
The Journal Impact Factor quartile is the quotient of a journal’s rank in category (X) and the total number of journals in the category (Y), so that (X / Y) = Percentile Rank Z.
- Q1: 0.0 < Z ≤ 0.25
- Q2: 0.25 < Z ≤ 0.5
- Q3: 0.5 < Z ≤ 0.75
- Q4: 0.75 < Z
InCites displays the best quartile for journals that appear in multiple Web of Science Research Areas. When a research area is specified, the quartile for that particular journal and research area is displayed.
Median age of the articles cited in the JCR year. Half of a journal's cited articles were published more recently than the cited half-life.
The Cited Half-life measures all of the cites earned by a publication (across all cited years) during the JCR year (i.e., citing year = JCR year). The cited half-life asks, if we take all those citations and sort them by publication-year-of-cited-item—we can split that body of citations directly in half: cites to younger cited item years (more recently published); and cites to older cited item years (less recently published). If we do this, how far back in time (from the JCR year) does that neat halfway split occur? The answer is the cited half-life. If a publication’s cited half-life is 4.6, this means that half the citations it earned (where citing year is JCR year) were to items published 4.6 or fewer years ago. And half were to items published longer ago than that.
What does 4.6 years mean? Or more specifically, what does the .6 decimal mean? We are not talking about items published up through the first 60% of whatever year (i.e., approximately August 7). An explanation of the calculation below.
Items counted in the Cited Half-life calculation are not papers themselves, but rather cites to those papers. If a paper was published in year X and got 5 cites during the JCR year, then the tally for year X goes up by 5 (once for each cite) – it does not merely go up by 1 (for the paper).
All the citations earned by Journal X (citing year = JCR year) to any year are essentially lined up in order of the cited item publication year. This body of citations is then split in half. The “location” of this split is the Cited Half-Life.
It will often be the case, when this happens, that on whatever year the split falls (e.g., 2011)—that year will be represented on both sides of the split. This will result in a cited half-life with a non-zero decimal. For example, there may be 60 cites to 2011 in the younger half, and 40 cites to 2011 in the older half. In the 2015 JCR this would result in a cited half-life of 4.6 years.
The Cited Half-life provides context for the “shelf life” (how long do they continue to be cited) and "timeliness" (how soon after publication do they begin earning most of the cites that they will ever earn) of items published in a publication.
A low cited half-life suggests citation activity that peaks and drops quickly. A high cited half-life suggests citation activity that peaks and drops more slowly (only peaks after a lag). Neither of these things are good or bad.
A journal will not receive a Cited Half-Life if it has earned fewer than 100 citations during the JCR year.
The Article Influence determines the average influence of a journal's articles over the first five years after publication. It is calculated by multiplying the Eigenfactor by 0.01 and dividing by the number of articles in the journal, normalized as a fraction of all articles in all publications. This measure is roughly analogous to the 5-Year Journal Impact Factor in that it is a ratio of a journal’s citation influence to the size of the journal’s article contribution over a period of five years.
The equation is as follows: where X = 5-year Journal Article Count divided by the 5-year Article Count from All Journals.
The mean Article Influence for each article is 1.00. A score greater than 1.00 indicates that e
The Immediacy Index is the average number of times an article is cited in the year it is published.
- The journal Immediacy Index indicates how quickly articles in a journal are cited.
- The aggregate Immediacy Index indicates how quickly articles in a subject category are cited.
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.
Because it is a per-article average, the Immediacy Index tends to discount the advantage of large journals over small ones. However, frequently issued journals may have an advantage because an article published early in the year has a better chance of being cited than one published later in the year. Many publications that publish infrequently or late in the year have low Immediacy Indexes.
For comparing journals specializing in cutting-edge research, the immediacy index can provide a useful perspective.
The Immediacy Index is similar to Journal Impact Factor, except the window for the numerator and denominator is restricted to the JCR year. This produces a same-year (one year only) variation on the Journal Impact Factor. The calculation therefore is:
This calculation helps provide an immediate glimpse into the citation data. Because peak citation usually takes several years, the Immediacy Index may not predict ultimate citation performance.
Items published late in the year are almost impossible to earn citations before the end of the year.
The Eigenfactor calculation is based on the number of times articles from the journal published in the past five years were cited in the JCR year. It also considers which journals contributed these citations, so highly cited journals influence the network more journal not cited as often. References from one article in a journal to another article from the same journal are removed so journal self-citations don't influence Eigenfactors.
A citation matrix is created and records citations from journal to journal (dropping self-citations). The citing year = JCR year. The cited period is the 5-year window prior to the JCR year (identical to the 5-year Journal Impact Factor).
For further detail on calculation of the Eigenfactor, please visit the Eigenfactor website.
The value of the Eigenfactor is similar to the Journal Impact Factor or the 5-year Journal Impact Factor. Unlike those, the Eigenfactor assigns weight or value to each earned citation, according to the citedness of the citing journal. Consider two journals: Journal A is highly cited; Journal B is poorly cited. Cites coming from Journal A are given greater weight when calculating Eigenfactors for journals B-Z, and cites from Journal B are given less weight when calculating Eigenfactors for journals A & C-Z.
The Eigenfactor, much like the Journal Impact Factor and 5-year Journal Impact Factor, is a publication-level metric. It does not apply to individual papers or subgroups of papers that appeared in the publication. It also does not apply to authors of papers, research groups, institutions, or universities.
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 calculated 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 Journal Impact Factor measurement is the same as the Journal, but with three more years added to the numerator and denominator. It's a five-year window instead of a two-year window. In the 2015 JCR, the five-year window included 2010, 2011, 2012, 2013 & 2014.
The calculation is factored exactly like the Journal Impact Factor, but considers a five-year window of citation data. The 5-Year Journal Impact Factor provides a broader view of the citation data, but at the expense of reduced granularity.
Like the Journal Impact Factor, the 5-Year Journal impact Factor is a publication-level metric. It does not apply to individual papers or subgroups of papers that appeared in the publication. Additionally, it does not apply to authors of papers, research groups, institutions, or universities. Also, the typical lag after publication of a paper until peak citation varies across papers, time, publications, and domains. When the lag is greater than two years, which it often is, a publication’s 5-year Journal Impact Factor tends to be higher than its Journal Impact Factor. Also, Journal Impact Factor and 5-year Journal Impact Factor are typically identical for the first two years a publication is covered in the JCR.
The Journal Impact Factor calculated after citations from journal articles to the journal in which they are published have been removed from the total count. A complete discussion of journal self-citation in Journal Citation Reports can be found here.
The Journal Impact Factor Without Self Cites is the same as Journal Impact Factor, but with one important exception. Any citations to a publication that come from the publication itself are excluded from the publication’s Journal Impact Factor without self-cites numerator.
The calculation is identical to the Journal Impact Factor in that the numerator is formed by the citations in the JCR year to items in year - 2 + citations JCR year to items in year -1 divided by citable items from the same years, but excluding self-citations.
This metric demonstrates the citations-per-item ratio without self-cites. This provides a publication-level metric where that publication’s direct influence on the metric has been removed. It highlights (at the expense of holistic measurement) the citation patterns toward a publication by its neighbors or peers.
Self-citation patterns vary considerably by publication and by subject category. For publications associated with a relatively small category (i.e., a domain of research where there are relatively few journals), relatively higher citation rates may be expected, because the domain’s entire body of research will necessarily be concentrated in relatively few publications. Self-citation is not a “bad” thing. but simply one of several metrics that provide data and context for publication-level evaluation.
The Journal Impact Factor is all citations to the journal in the current JCR year to items published in the previous two years, divided by the total number of scholarly items (these comprise articles, reviews, and proceedings papers) published in the journal in the previous two years.
Though not a strict mathematical average, the Journal Impact Factor provides a functional approximation of the mean citation rate per citable item. A Journal Impact Factor of 1.0 means that, on average, the articles published one or two years ago have been cited one time. A Journal Impact Factor of 2.5 means that, on average, the articles published one or two years ago have been cited two and a half times. The citing works may be articles published in the same journal. However, most citing works are from different journals, proceedings, or books indexed in Web of Science.
The Journal Impact Factor takes into account the outbound cited references from any of the five journal and proceedings indexes in Web of Science (Web of Science):
- Science Citation Index Expanded (SCIE)
- Social Sciences Citation Index (SSCI)
- Arts & Humanities Citation Index
- Conference Proceedings Citation Index, Science edition
- Conference Proceedings Citation Index, Social Science and Humanities edition
- For each title in SCIE or SSCI (only these two indexes get JIFs), the citations it earns (among the outbound citations measured), are collected and summed.
This collection and summation takes into account the year of publication for the outbound citation (=JCR year) and the cited item. The Journal Impact Factor is restricted to a two-year window of interest for cited item publication year: one year prior to the JCR year (= year -1) and two years prior to the JCR year (= year -2).
For example, in the 2015 JCR, each Journal Impact Factor will measure the citations earned by a publication where the citing year is 2015, and the cited year is either 2013 or 2014.
Also, because the Journal Impact Factor is ultimately a ratio of citations earned (in the given window) to citable items published (in the same window) by a publication, a count must be made of all the items published (and of the subset deemed to be “citable”) in that publication during that window. In the ratio, the number of citations earned is the numerator. The number of citable items is the denominator.
The value of the denominator is restricted to the same window of time as the numerator: year -1 and year -2. The denominator includes any item in Web of Science with the document type of Article or Review. Excluded from the denominator is an item with any other document type.
The Web of Science production database is the venue for measuring these data points. This database is constantly taking in new data, and correcting or updating old data. This degree of flux makes producing a metric like the Journal Impact Factor difficult, because the data inputs are likely to change from minute to minute. As a result, the JCR team fixes a date, usually in the spring of the year following the JCR year, when they take an indelible snapshot of the database. This is JCR extraction, which calculates all JCR metrics.
The Journal Impact Factor Formula
Journal Impact Factor = (citations from JCR year to items in “year -2” + citations from JCR year to items in “year -1”)/ (citable items in “year -2” + citable items in “year -1”)
The Journal Impact Factor is a publication-level metric. It does not apply to individual papers or subgroups of papers that appeared in the publication. Additionally, it does not apply to authors of papers, research groups, institutions, or universities.