Journal Impact Factors: Part I

April 7, 2016

Dr. Jennifer C van Velkinburgh


Assessing the quality, integrity and trustworthiness of scientific and medical data, even when published in a peer-reviewed journal, is not a straightforward task – even for the researchers who are publishing that data and their peers who are reviewing it. While many metrics have been developed to track, monitor and assess the influence of a journal (and by extension the findings presented within its pages), one of the most recognized, established and accessible is the Journal Impact Factor (JIF).


What is a Journal Impact Factor?

Invented in the 1960s by Thomson Reuters, the JIF is a quantifiable measure of a journal’s influence in its field, and is simply the calculated citation frequency of an average article in that journal for a particular year (i.e. the most current IF is based on citations garnered in the previous year). Thomson Reuters began publishing their annual Journal Citation Report (JCR) of their Science Citation ‘Index’ in 1975. Since then, gaining inclusion in the JCR has become the brass ring reached for by every scientific and medical journal hoping to gain respectability (and with that, submitting authors, paying subscribers, more citations, and greater revenue). Currently, over 10,000 journals are included in the JCR; the list of journals included in the latest (2014) JCR can be found at: (simply change the year to find other years’ reports).


JIFs range from >50 to zero values (such as 0.12), with the greatest amount under 4 and many ranging between 1 and 2. Journals are given an IF when they are ‘indexed’, the process of which includes validation of a journal’s peer-review process for accessing articles for publication.