How can I measure the impact or importance of a journal article or book?

Note: for a more complete answer to this question, see the JHU libraries’ Scholarly Metrics guide.

There are a number of metrics used to calculate the impact of scholarship in the sciences and social sciences (see below for the humanities). The most common rely on some count of the number of times an article has been cited in other articles. The two biggest sources of this information are Web of Science (WoS) and Scopus.

Journal metrics

Journal impact factor ranks a journal by the number of citations its articles receive relative to other journals in the field. You can find impact factors in the “Journal Citation Reports” section of the Web of Science database. Look for it along the ribbon at the top of the page. Scopus, which Harvard does not subscribe to, allows free lookup of its “CiteScore” calculation for journals. Additionally, Scimago Journal & Country Rank is a free resource that uses Scopus data.

Article metrics

Article times cited: the main search interface in Web of Science displays the number of times an article has been cited in the journals tracked by WoS. You can also sort your results by number of citations, so that the most-cited articles are at the top of the list. Google Scholar also calculates times cited, but please note that Google’s total citation counts are inflated because the algorithmic analysis used to produce them returns many false positives.

Usage factor calculates the number of time an article has been downloaded. It is one of a number of “altmetrics” designed as complementary alternatives to the more traditional citation-based metrics such as a journal's impact factor. Project Counter is an effort to set standards for reporting such download information and encouraging library database vendors to participate.

Author metrics

H-index ranks authors based on how many times all of their publications have been cited.

In Web of Science:

From the main search page, select “author” instead of “topic.”

1. Search by last name and first initial (Smith, J).
2. Click on any article in your results that is by the author you’re looking for.
3. Click on the author’s name.

This will run a search for all articles by that author: now you can click on “create citation report” at the top right of the page to run a calculation of the author’s H-index from those articles.

Other resources:

Scopus, which Harvard does not license, offers a free author lookup.

Microsoft Academic and Google Scholar (Profiles search) both offer metrics for specific authors.
 

A note on the humanities

While the above metrics often exist for publications and scholars in the humanities, they are not always the best option. The metrics favor the publishing format (journals) and timescale (e.g. 2 years) of the sciences, which makes them less insightful for humanities scholarship. They are also less accurate, as the coverage is much less complete and less representative of the field’s scholarly output.

One of the main ways of determining scholarly impact in the humanities is via citing authors’ descriptions. These can be found via:

• Book reviews published in academic journals.

• Scholarly guides, companions, and encyclopedias, which identify the most important contributions to a field or topic.

• Individual references. It is harder to conduct a balanced search for these, but the “snippet” view available in many full-text databases can be very helpful. See our FAQ on conducting cited reference searches.

For much more extensive and detailed information, see the excellent guide to Scholarly Metrics maintained by librarians at Johns Hopkins University.