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Impact Metrics

What is the Author Impact?

Photo by Aaron Burden on Unsplash (cropped image)

Author impact metrics are indicators used to evaluate the impact of the academic publications of an author, a lab or an institution.

They are based on the number of citations and the number of publications.

The most recognised author metrics is the h-Index.

G-index and i10-index are alternatives to h-index. Please note that many other author metrics exist, but most of them are quite difficult to analyse.

H-Index, the Most Used One

H-index (or Hirsch index), is the most used author metric. It was created by the physicist Jorge E. Hirsch in 2005 (Hirsch, J. E. “An Index to Quantify an Individual’s Scientific Research Output.” Proceedings of the National Academy of Sciences - PNAS 102.46 (2005): 16569–16572. Web.).

It is based on the number of publications and the number of citations.

Keep in mind: 

  • 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-index because of the coverage (years, kind of sources) of each database. According to Harzing, A. W., & Alakangas, S. (2016). Google Scholar, Scopus and the Web of Science: a longitudinal and cross-disciplinary comparison" Scientometrics, 106(2), 787-804, the average h-index for the Social Sciences is:

    • 9.6 in Web of Science
    • 12.00 in Scopus
    • 21.5 in Google Scholar
  • 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 H-index corresponds to the number of articles (N) on a list of publications ranked in descending order by the times cited that have N or more citations.

If somebody has an h-index of 5, it means that 5 of his articles have been cited at least 5 times each.

Articles Citations
1 46
2 25
3 12
4 11
5 5 = H-Index
6 4
7 2
8 1

 

 

 

 

 

 

 

 

 

Wikimedia Commons http://en.wikipedia.org/wiki/File:H-index-en.svg

Keep in mind:

  • The same author h-index may vary from one database to another, depending on the coverage of each database
  • Co-publishing can elevate the h-index, because it does not take the order of authorship into account
  • Time helps to increase the h-index; as it does not take into account the longevity of a researcher's career, it favours more experienced researchers over those at the beginning of their careers.
  • The subject area can affect the h-Index: a researcher who publishes on a trendy subject will have a higher h-index than another one who publishes on a niche topic
  • The language of the publication affects the h-index; publications written in English receive more citations
  • Open access publishing increases the visibility of articles and their chance to be cited
  • Promotion of publications (blog posts, academic social networking, preliminary research findings at conferences,...) helps to make articles more visible and increases their chance of being cited
  • H-index takes self-citations into account; some high h-indexes are due to self-citation abuses

Keep in mind:

Before consulting your h-indexes, do not forget that different databases will give different h-indexes because of the coverage (years, kind and quantity of sources) of each database:

Scholar Citations
Publish or Perish (Free downloadable software for academic citations analysis)
Scopus Author Profile (Elsevier)
  • Coverage
  • Free access to author's h-index, total citations
  • Updated: daily
Web of Science - Social Sciences Citation Index (Bibliographic database)
  • Coverage (from 1900 - present for some journals): less content than Scopus in the social sciences
  • Search by author name or researcher identifier (ORCID or ResearchID) and click on “create citation report” in the upper right corner
  • Citation report includes: h-index, visual presentation of publications per year and citations per year, total times cited, average times cited
  • Updated: weekly

Alternatives: g-index, i10-index

"G-index is introduced as an improvement of the h-index of Hirsch to measure the global citation performance of a set of articles. If this set is 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" (Egghe, L., “Theory and practice of the G-index”. Scientometrics, vol. 69, no. 1, (2006), pp. 131–152).

Keep in mind:

  • The g-index gives more weight to highly-cited articles (whereas the h-index is insensitive to it)
  • Someone's g-index will always be equal to or greater than the h-index
  • You can consult your g-index through Publish or Perish (free downloadable software for academic citations analysis)

The i10-index was created by Google Scholar (Google Scholar Blog, 2011):

i10-Index = the number of publications with at least 10 citations

Keep in mind:

  • It is only accessible from Google Scholar Citations (author profile) (you need a Google account to manage your profile)
  • The i10-index is easy to calculate