If you are a novice researcher planning to write an article, “impact factor” is one of the terms you will hear most from more senior researchers around you. The impact factor is a numerical value that shows how many citations the articles published in a journal get on average.

While calculating the impact factor for each journal, the number of articles published in that journal in the previous two years and the citations received by those articles are included in the calculation. The impact factor for that year is determined by dividing the number of citations by the number of published articles. Since a high impact factor indicates that the articles published in that journal are generally highly cited, the impact factor has become a measure of the prestige of journals over time.

The impact factor is one of the oldest internationally recognized bibliometric criteria used in evaluating journals. Impact factors of journals have been published as an annual list (Journal Citation Reports [JCR]) since 1975. This list was prepared by the private company Thomson Reuters for many years, and today Clarivate Analytics continues this mission.

Important points should not be forgotten when talking about the impact factor: Letter to the Editor and Congress Proceedings type publications are not used in calculating the impact factor. In general, Review type publications receive more citations, while Case Report type publications receive fewer citations. The types of articles published in the journal, the topics of the articles, and the number of researchers in the journal’s coverage directly affect the impact factor. For example, journals that publish articles in a specialized field where few researchers work are unlikely to achieve a high impact factor. The impact factor is heavily criticized because some publication types are excluded in the calculation, the evaluation covers only two years, and the analysis includes self-citations. Many new bibliometric criteria have recently been introduced as an alternative to the impact factor.

You can find more information on the impact factor and its calculation in Part 1: Basics of Medical Writing of our Internet site.