University Libraries

Researchers do not have impact factors, but journals do!

The impact factor of an academic journal is a measure reflecting the average number of citations to recent articles (2-3 years) published in that specific journal. It is often used as a metric for the relative importance and/or impact of a journal within its field.

Flow chart created by Hanna Schmillen, 2014.

Things to Consider about Impact Factors:

1. Many journals do not have an impact factor, that doesn't mean they are bad journals. They may be new and turnover of research is SLOW.
2. The impact factor cannot assess the quality of individual articles. Even if citations were evenly distributed among articles, the impact factor would only measure the interests of other researchers in an article, not its importance and usefulness.
3. Only research articles, technical notes and reviews are “citable” items. Editorials, letters, news items and meeting abstracts are “non-citable items” but can influence the number of citations/articles, which in turn effects the impact factor.
4. Only a small percentage of articles are highly cited and they are found in a small subset of journals. This small proportion accounts for a large percentage of citations.
5. Controversial papers, such as those based on fraudulent data, may be highly cited, distorting the impact factor of a journal.
6. Citation bias may exist. For example, English language resources may be favored. Authors may cite their own work.

Other Journal Impact Rankings Calculations:

Scopus CiteScore will tell you the number of citations in a journal in the current year in relation to all the documents published in that journal in the prior thee years. It represents the average number of citations that a given document (article, book series, conference proceeding, letter, etc) in a three year period. The Source Details screen on Scopus displays how the score for the individual journal is calculated.

Cabell's Scholarly Analytics provides information about some journals' acceptance rates, peer review method, the amount of time the review takes and how many reviewers are involved. Further, it includes the scite Index (SI) measurements which is calculated using the following formula: # supporting cites/ # supporting sites + # contrasting cites. Additional information includes the impact factor from Journal Citation Reports, the level of open access, and an “Altmetric Report” that includes social media and other internet activity.

Google Scholar's Metrics will tell you about impact factors among other bibliometric information. On the main page of Metrics, you can search by field or specific journal. There is also a listing of top journals based on the h5-index and median.

Explanation of H5-index and H5-median

The H5-index is created by Google Scholar, and is similar to the h-index explained in Author-level Metrics.

H5-index "It is the largest number h such that h articles published in [the past 5 years] have at least h citations each". Thus, an H5-index of 60 means that that journal has published 60 articles in the previous 5 years that have 60 or more citations each.

H5-median is based on H5-index, but instead measures was the median (or middle) value of citations is for the h number of citations. A journal with an H5-index of 60 and H5-median of 75 means that, of though 60 articles with 60 or more citations, the median of those citation values is 75.

To the right is a chart listing the top 20 English-language journals ranked by the H5-index.

Availability

Both the H5-index and H5-median are available in Google Scholar Metrics. Journals can be browsed by discipline (more information about disciplines is available in Journal Rankings) or searched by keyword.

Limitation

Google Scholar Metrics will only display the top 20 journals for each subject category. Additionally, there is no historical data.