The h-index evaluates the productivity and impact of a set of publications, most commonly the publications by a researcher. It is the highest possible value where there are publications with at least the same number of citations, within a set of publications.

Example of a h-index

A researcher with the h-index of 9 has 9 publications with at least 9 citations each and the rest of the publications have less than 10 citations. The researcher in this example does not fulfill the requirement to have 10 publications with at least 10 citations. This is expressed in the graph below.

Characteristics of the h-index.

  • Both productivity and impact is expressed.
  • A single highly cited publications can not affect the index with more than 1 (in contrast to mean values).
  • Relatively easy to understand since the index explicitly reflects counts of publications.
  • The index normally looks at a whole research career, hence favoring senior researchers.

Disadvantages of the h-index

  • Not neutral to the research field. It is easier for researchers within some research fields to get a high index since publication patterns varies.
  • It does not take into account the number of researchers per publication (there are alternative metrics that do).
  • The index is affected by the number of indexed publications within the database and will therefore vary between databases (e.g. Web of Science, Scopus and Google Scholar). 

 References/More info

Hirsch, J. E. 2005. ”An index to quantify an individual’s scientific research output”. Proceedings of the National Academy of Sciences of the United States of America 102 (46) (November 15): 16569–16572. URL: dx.doi.org/10.1073/pnas.0507655102

Schreiber, M., C.C. Malesios, och S. Psarakis. 2012. ”Exploratory factor analysis for the Hirsch index, 17 h-type variants, and some traditional bibliometric indicators”. Journal of Informetrics 6 (3) (Juli): 347–358. URL: dx.doi.org/10.1016/j.joi.2012.02.001

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