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Course Research Impacts: Important metrics

Important metrics

Here we introduce the most important metrics: the H-index on the author level, and the journal metrics: Journal Impact Factor, SCImago Journal Rank and Source Normalized Impact per Paper. In this course you will find out more about the calculation of these metrics and how you can retrieve them.

Author level metric: The H-index

The H-index, proposed by J.E. Hirsch in 2005, is a way to measure the individual academic output of a researcher. A researcher has “index h if h of his or her Np papers have at least h citations each and the other (Np-h) papers have ≤h citations each” (Hirsch, p. 16569).

To calculate the H-index you need the list of the publications of the researcher and the number of citations each publication received. Then sort the publication list by the number of citations: the publication with the highest number of citations is number 1. The H-index is the number where the number of the publication in the list and the number of citations received are the same.

The H-index has become a popular performance indicator, problably because the calculation of the h-index is easy to understand, and because it takes a quantative aspect (the number of publications ) and a qualitative aspect (the number of citations received) into account. However, there are various weak points. An easy example: the H-index doesn’t take the age of the researcher into account, which makes it unfair to use the H-index to compare two researchers in different stages of their research life. A number of alternative H-indices have been proposed, some of them we will encounter later.

In this course we show you how to find the H-index in Web of Science, Scopus, Publish or Perish and Google Scholar Citations (see the chapters below).

Up-to-date information about the h-index can be found in Wikipedia (https://en.wikipedia.org/wiki/Hirsch_number). For calculating the H-index you can also have a look at the MyRI (Measuring your Research Impact) website.

Journal metrics

Journal metrics, once developed to investigate the scholarly communication system, are used for different reasons:

  • By librarians to decide which journals the library should subscribe to
  • By publishers and editors to see how their journal is doing compared with other journals
  • By researchers to decide in which journal to publish
  • By research managers in the assessment of research performance.

The Journal Impact Factor (JIF, published in the Journal Citation Reports) is the oldest journal metric. One major point of critique is that the JIF doesn’t take into account that disciplines have distinct citation characteristics. Therefore, other metrics have been developed, among others CiteScore, SJR (SCImago Journal Rank) and SNIP (Source Normalized Impact per Paper). These metrics are available in Scopus and are based on Scopus data. SJR weights citations, not all citations get the same value. SNIP takes into account the citation potential of the subject field of the journal.

See for more information about the use of SJR and SNIP the article by Colledge et al. (2010).