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Journal Citation Reports: For Librarians

Journal Citation ReportsĀ® offers a systematic, objective means to critically evaluate the world's leading journals, with quantifiable, statistical information based on citation data.

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Cited Half-Life: What depth of content is getting cited?

Cited Half-Life looks at the citations that a journal receives (incoming citations) in the current JCR data year. This metric can help you understand the age of publications, that are currently getting cited. Journals can receive citations in one JCR year to anything that they have ever published, and the Cited Half-Life helps you understand how far back researchers go, when they cite that journal. 

The Cited Half-Life is the median age of a journal's articles that were cited in the JCR year. Half of a journal's cited articles were published more recently than the Cited Half-Life. For example, a 2015 Cited Half-Life value of 7.0 for Journal X means that half of the Journal X papers that were cited in 2015 were published in the last 7 years.

This information can help you assess backfile purchases for a journal. Cited Half-Life is displayed in the Key Indicators table on a journal profile page, and it can be added to a journal ranking on the JCR homepage. 

Navigate to the Cited Journal Data section to view the specific journals contributing citations to the parent journal. The Cited Half-Life Data in the Cited Journal Data section shows you the number of citations in the citing year that went to journal content published in a particular cited year. Below the raw number of citations, a cumulative percentage is displayed. This shows you the percentage of total citing year citations that have been accrued as you move backward in time. 

Cited Half Life Data

Example: This journal's 2015 (cited year) source material was cited 3,485 times in 2017 (citing year). The total citations to the journal's 2015-2017 content makes up 19.12% of 2017 citations to the journal. When you reach the cumulative percentage mark of 50%, you have reached the Cited Half-Life for the journal.

The Cited Journal Data graph is a visualization of the Cited Half-Life Data. The stacked column shows the number of citations occurring in the citing year to the cited year's journal content. The yellow portion of the column refers to the number of self-citations in that total count. The Cited Half-Life is marked by the grey line. 

Cited Journal Graph

The Cited Journal Data table reveals the relationships between the citing journals and the selected cited journal. Impact refers to the Impact Factor score for the citing journal. The All Yrs column shows you the total number of citations coming from each journal in the citing year. That citation count is then broken down by cited year. 

Cited Journal Data table

Example:  PLOS ONE cited our selected journal 906 times in 2017. Those citations referenced material published in any year within the journal's backfile. This table shows me that 105 of the 2017 citations from PLOS ONE cited 2014 papers from the selected cited journal, and 77 of the 2017 citations from PLOS ONE went to 2015 papers.