Skip to Main Content

Scholarly Communication Guide: How to measure impact

This guide provides information on the support services available at the library to help with all stages of your research, from planning your research, to measuring the impact of your research.

Metrics for measuring Impact

This guide details various ways of measuring research impact, particularly through traditional means of publishing and citation.  Before you begin to delve into the various citation metrics, we recommend you do the following three things:

  • Sign up for an ORCID Identifier:  The Open Researcher Community ID is an increasingly recognized persistent digital identifier.  The unique number assigned to you will allow publishers and aggregators of scholarly literature to distinguish you from researchers with similar names.  This is a powerful tool in author disambiguation and it takes just a few minutes to sign up. Go to orcid.org and follow the instructions to register for your ORCID identifier.
  • Get a ResearcherID with Web of Science:  A ResearcherID can be linked to your ORCID number and facilitates citation metrics and publication tracking using Web of Science tools.  With a ResearcherID, you will be included in the Web of Science author index allowing other researchers to learn more about your work and affiliations.  
  • Create a Google Scholar Citations Profile:  Google scholar citations allows authors to track citations to their scholarly works and to calculate numerous citation metrics based on Google Scholar citation data.  By setting up a profile, you will be able to disambiguate yourself from authors with the same or similar names.  For more information, see the Google Scholar page in this Library Guide

The h-index was developed in 2005 by J.E. Hirsch as a method for quantifying the relative impact of an author by counting the number of citations to his or her publications.An author has an index of if there are at most h papers that have been cited at least h times. The h-index is calculated by counting the number of publications for which an author has been cited by other authors at least that same number of times. For instance, an h-index of 17 means that the scientist has published at least 17 papers that have each been cited at least 17 times. If the scientist's 18th most cited publication was cited only 10 times, the h-index would remain at 17. If the scientist's 18th most cited publication was cited 18 or more times, the h-index would rise to 18.

Points to remember:

  • The H-index measures the production and impact of a researcher or group of researchers (all being evaluated equally, whatever their rank on the publication)

  • H-indexes cannot be compared across disciplines, as they are affected by each discipline's citation traditions and methods

  • Different databases will give different H-indexes because of the coverage (years, kind of sources) of each database.

  • It is generally recommended to choose the most advantageous H-index. As it changes over time, when you need to share it, do not forget to indicate where and when you found it

  • All citations are taken into account, whether positive or negative

 

The G-index was proposed by Leo Egghe in 2006 as an improvement on the H-index. The G-index is calculated based on the distribution of citations received by a given researcher's publications, such that: given a set of articles ranked in decreasing order of the number of citations that they received, the G-index is the unique largest number such that the top g articles received together at least g2 citations.

For example, a G-index of 20 means that an academic has published at least 20 articles that, combined, have received at least 400 citations. However, unlike the H-index, these citations could be generated by only a small number of articles. For instance, an academic with 20 papers, 15 of which have no citations, with the remaining five having respectively 350, 35, 10, 3 and 2 citations, would have a Gg-index of 20, but a Hh-index of 3 (three papers with at least 3 citations each).

Disadvantages of the G Index:

  • Introduced in 2006, and debate continues whether G-Index is superior to H-Index.  Might not be as widely accepted as H-Index. 

M-Index

The m-index, also proposed by Hirsch, is defined as the h-index divided by the number of years since the researcher’s first publication. The index is meant to normalize the h-index so that early- and late-stage scientists can be compared. The m-index averages periods of high and low productivity throughout a career, which may or may not be reflective of the current situation of the scientist.