Research Guides: Measuring Research Impact: Journal Metrics

Journal Impact Factor

Journal Citation Reports is an excellent source for determining journal impact factor. It provides impact factors (over the two years citation period) and rankings for approximately 12,000 scholarly and technical journals and conference proceedings in the areas of science, technology, and the social sciences.

The Journal Impact Factor is a ratio devised as a measurement of the average citedness (and, by extension, importance) of a journal. It is calculated by dividing the number of citations of a particular publication in a certain year by the number of citable articles published in the journal in the previous two years. Other related measurements may also be calculated, such as the Five-year impact factor (which looks at the previous 5 years) and the Immediacy index (which is the average number of times an article is cited in the year it is published).

Like author impact measurements, journal impact measures can be only so informative, and researchers in a discipline will have the best sense of the top journals in their fields.

Limitations of the Journal Impact Factor:

Experts stress there are limitations in using the journal impact factor to evaluate a scholar's work. There are many reasons cited for not relying on this measure alone to evaluate the output of a particular individual, including:

A single factor is not sufficient for evaluating of an author's entire body of work.
Journal impact factors are meaningless unless compared within the same discipline. Impact factors vary between disciplines.
The journal impact factor was originally devised to show the impact of a specific journal, not a specific author. The quality and impact of the author's work may extend beyond the impact of a particular journal.

According to Jim Testa, a researcher for ThomsonReuters Scientific, the most widespread misuse of the Impact Factor is to evaluate the work of an individual author (instead of a journal). "To say that because a researcher is publishing in a certain journal, he or she is more influential or deserves more credit is not necessarily true. There are many other variables to consider." (interview 6/26/2008 in Thomson Reuters blog entry)

Eigenfactor and Article Inflence Scores

What is the Eigenfactor score?

The Eigenfactor score reflects importance or prestige of a scientific journal. Created to help capture the value of publication output vs. journal quality (i.e. the value of a single publication in a major journal vs. many publications in minor journals). It considers not only the number of times in the last five years articles from a journal have been cited during the JCR year, but also the source of those citations. Citations from highly rated (i.e. impactful) journals make a larger contribution to a journal's Eigenfactor score than citations from lesser journals.

Eigenfactor scores are scaled so that the Eigenfactor scores of all journals listed in Thomson's Journal Citation Reports (JCR) sum to 100. Thus if a journal has an Eigenfactor score of 1.0, it has 1% of the total influence of all indexed publications. In 2013, the journal Nature has the highest Eigenfactor score, with a value of 1.603.

NOTE: Eigernfactor scores are also displayed in Journal Citation Reports.

What is the Normalized Eigenfactor score?

The Normalized Eigenfactor score is scaled so that the average journal has a score of 1. Journals can then be compared and influence measured by their score relative to 1; a journal with a Normalized Eigenfactor Score of 3 has three times the total influence of the average journal in the JCR.

What is the Article Influence Score?

Measures the average influence, per article, of the papers in a journal. Article Influence scores are normalized so that the mean article in the entire Thomson Journal Citation Reports (JCR) database has an article influence of 1.00. For example, in 2006, the top journal by Article Influence score is Annual Reviews of Immunology, with an article influence of 27.5 . This means that the average article in that journal has twenty seven times the influence of the mean article in the JCR.

Advantages of Eigenfactor/Article Influence Score:

Eigenfactor scores and Article Influence scores adjust for citation differences across disciplines.
The Eigenfactor and AL scores are calculated based on the citations received over a five year period

Disadvantages of Eigenfactor/Article Influence Score:

Eigenfactor assigns journals to a single category, making it more difficult to compare across disciplines.
Some argue that Eigenfactor score isn't much different than raw citation counts (see this blog post, for example).

Other Citation Based Metrics

Google Scholar H5-index and h5-median The h5-index is equivalent to the Hirsch index, but calculated for a journal rather than an author, over a 5 year period. A h5 of 10 means that during the past five years a journal has published 10 articles which were each cited at least ten times. The h5-median is the median number of citations of the articles making up the h5-index

NIH iCite Analysis For health sciences, the NIH’s Relative Citation Ratio is an interesting article-level metric. It takes into account differences in fields (some publish more articles and have more journal options than others). The tool can be searched by author, article title, or MeSH keyword.

Scopus Scopus is a large citation database of peer-reviewed literature: scientific journals, books and conference proceedings with over 22,000 titles from more than 5,000 international publishers. You can use this free author lookup to search for any author.

SCImago Journal Ranking (SJR) A portal that includes the journals and country scientific indicators (normalized on a scale of 0 to 100) developed from the information contained in the Scopus database. It provides the major alternative to Web of Science's impact factor.

Semantic Scholar is a free, AI-powered search and discovery tool that helps researchers discover and understand scientific literature that's most relevant to their work. It covers 175 million papers in all scientific disciplines.

Source Normalized Impact per Paper (SNIP) SNIP is closely related to, but independently calculated and maintained from, SCImago's SJR. Its metric, Raw Impact per Paper (RIP) is comparable to both impact factor and SJR.

Non-Citation Based Metrics

Subscription to/Circulation of a Journal

This metric indicates the size of the audience for a particular journal. Generally speaking, the greater the circulation the greater the importance. This information is sometimes made available on the publisher's website, or it may be obtained by contacting the journal's editor. For a quick figure, check WorldCat.

The Acceptance Rate of a Journal

Journals with lower article acceptance rates are more selective and, therefore, regarded as more prestigious. Being published in one of these journals tends to be viewed very positively during the tenure review process. Cabell's is a great place to find this information. Another place you might find acceptance rate is in the 'Information for Authors' section of the journal's website. If all else fails you can contact the Editor of a journal to see if he/she will share its acceptance rate with you.

Is the Journal Peer Reviewed?

Being peer reviewed is a commonly accepted indicator of rigor and credibility. Ulrich's Periodicals Directory will let you know whether a journal is peer reviewed.

Where is the Journal Indexed?

Prominent journals tend to be indexed in a variety of disciplinary-specific and general databases. Ulrich's will provide a list of the databases in which a journal's contents can be found.