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Journal Citation Reports - The Impact Factor and Other Metrics: Immediacy Index

A brief introduction to using JCR for locating and interpreting the impact factor for journals. Included is the Eigenfactor metrics and other aggregate impact factors.

Immediacy Index

The Immediacy Index is the average number of times an article is cited in the year it is published.
  • The journal Immediacy Index indicates how quickly articles in a journal are cited.
  • The aggregate Immediacy Index indicates how quickly articles in a subject category are cited.
The Immediacy Index is calculated by dividing the number of citations to articles published in a given year by the number of articles published in that year.

Because it is a per-article average, the Immediacy Index tends to discount the advantage of large journals over small ones. However, frequently issued journals may have an advantage because an article published early in the year has a better chance of being cited than one published later in the year. Many publications that publish infrequently or late in the year have low Immediacy Indexes.

For comparing journals specializing in cutting-edge research, the immediacy index can provide a useful perspective.  The example below shows journals ranked by the Immediacy Index in the category of Developmental Biology.


Here is the calculation for the immediacy index number.

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