Faculty Toolkit: Scholarly Communication: Impact Metrics

Impact factor: The average number of citations received per paper published in that journal during the two preceding years. Data comes from Journal Citation Reports and Web of Science.  

Immediacy index: The number of citations the articles in a journal receive in a given year divided by the number of articles published.

Cited half-life: The median age of the articles that were cited in Journal Citation Reports each year. For example, if a journal's half-life in 2005 is 5, that means the citations from 2001-2005 are half of all the citations from that journal in 2005, and the other half of the citations precede 2001.

CiteScore:  The number of citations to documents by a journal over a four-year period.  Data comes from Scopus.

H-index:  A journal's number of articles (h) that have received h citations over a specific time period.  At first considered an author-level metric, it is now being applied to journals. 

Various services provide journal metrics. Each has a unique approach to measuring a journal's importance to its field.

With today's online publication and social media tools it is now possible not only to track an individual article's impact via citations, but to use new measures of scholarly and social visibility. Many scholars are now using these metrics in support of promotion & tenure and to create real-time vitae. Article-level metrics include:

• Usage: Number of times an article has been viewed, accessed, or downloaded on a publisher's site, PubMed Central, or other repository.
• Captures: Number of times has an article been captured on peer recommender systems such as Mendeley.
• Social bookmarking and dissemination activity: Measures can include Facebook likes, LinkedIn shares, and tweets.
• Media and blog coverage: Mentions by the popular press and blogs.
• Discussion activity and ratings: Social media activity can indicate the article's merits, immediacy, and importance.

More on article-level metrics.