The world of scholarly publishing has long sought an objective way to evaluate the relative importance of a journal. This is a key question not only for authors but for librarians looking to make decisions regarding their journal collection. In 1975, this led to the creation of the Impact Factor.
The Impact Factor explained
Created by Eugene Garfield, founder of the Institute for Scientific Information (ISI), the Impact Factor is one objective means of evaluating a medical journal — and comparing the journals in a given specialty. Today, the Impact Factors are published annually in Journal Citation Reports by Clarivate Analytics.
A journal’s Impact Factor is the ratio of the number of citations it received over a two-year period to the number of citable items it published over the same period. The formula is as follows:
| Impact Factor in Year X = | # of citations to Journal X in the past 2 years |
| # of total citable items by Journal X in the past 2 years |
As useful as the Impact Factor is, it should not be the only factor that you use in assessing a journal. Some discernment is called for when looking at a journal’s Impact Factor. For example, some journals have very high Impact Factors due solely to the fact that they publish a small number of highly cited articles. They are on the sweet side of the mathematical calculation. Conversely, there are high-quality journals with a lower Impact Factor due to the large number of citable articles it publishes.
An alternative to Impact Factor: Eigenfactor
The Eigenfactor was developed in 2007 by Jevin West and Carl Bergstrom at the University of Washington as an alternative to the Impact Factor. It measures the number of times articles from the journals published in the past five years have been cited in Journal Citation Reports (JCR).
One key difference between the Eigenfactor and Impact Factor is that while the Impact Factor does not consider the sources of citations, the Eigenfactor does. With the Eigenfactor, citations from highly ranked journals are weighted to make a larger contribution to the metric than those from poorly ranked journals.
Another difference is Eigenfactor’s five-year window mentioned above versus the Impact Factor’s two-year window. Also, the Eigenfactor counts citations to journals in social sciences and humanities, and it eliminates self-citations.
What’s in a number?
Authors should consider multiple metrics when deciding where to submit a manuscript because the difference between a journal’s Impact Factor and its Eigenfactor can be striking. For example, Medicine® has an Impact Factor of 1.889, which ranks it 99th of 169 journals in the General & Internal Medicine category of the most recent Journal Citation Reports. But when you rank the category by Eigenfactor, Medicine is ranked 7th.
The decision of where to submit a manuscript for publication is a critically important one, and some due diligence by authors is in order. In the end, it is helpful to look at multiple metrics and fortunately, authors today looking to publish have multiple ways of evaluating a journal.
Learn more
Journal Citation Reports (Clarivate Analytics)
Eigenfactor.org
Resources for authors
Author Webinars
Editorial Services for Authors
Frequently Asked Questions About Open Access
Lippincott Author Talk archives
Lippincott’s Open Access page
Lippincott’s Gold Open Access Journals (listed by specialty)
