Measuring Research Impact: Author Metrics


Citation Counts

Citation counts measure the impact of an individual author by counting the number of times he/she has been cited in other works. This count of a particular author's work is one of the components used to evaluate scholarly output and the impact he or she is having upon a particular discipline. Although such counting sounds relatively straightforward, it is complicated by the fact that there is no single citation analysis source that covers all publications and their cited references.

There are a number of ways to measure this:

  • Citation count -- the total number of times an author's work has been cited
  • Average citation rate -- the ratio of total citations to the number of works authored
  • The h-index 
  • i10-index  - a simple measure of impact, this metric is only used by Google Scholar.

Citation analysis as a qualitative measurement should be used cautiously, for the following reasons:

  • Citation rates and practices vary widely between disciplines.  Citation analysis of scholars in one field should not be compared to those in another.
  • Where a scholar publishes can have a great impact on the analysis if the tools used to count citations do not index the publications where a scholarly work is cited. This is particularly true for those that publish in international journals, smaller regional or local publications, or in non-journal sources such as books.
  • Citation rates can be influenced by practices such as self-citation.

The h-index

The h-index, or Hirsch index, has traditionally been used to measure the number of significant papers an individual scholar has published, though it is also used to determine the numbers of significant articles published by individual scholarly journals. Rather than a measure of the average number of citations, which can be skewed by either a single highly-cited article and by very new articles which have not yet been cited, the h-index is an attempt to provide a measurement that avoids over-emphasizing outlier citations. The index is intended to improve upon simpler measures such as simple citation counts or number of publications. Be aware the index works properly only when comparing scholars working in the same field, as citation conventions differ widely between fields.

H-Index = number of papers (h) with a citation number ≥ h.  

Example: a scientist with an H-Index of 23 has 23 papers cited at least 23 times.  

Advantages of the H-Index:

  • Allows for direct comparisons within disciplines
  • Measures quantity and impact by a single value
  • Is a good tool for comparing researchers with large numbers of publications

Disadvantages of the H-Index:

  • Does not give an accurate measure for early-career researchers since they have only a small number of papers
  • Uses citations as a benchmark, and in many cases an article does not begin to be cited by others until years after it has been published

Tools for measuring H-Index:

Google Scholar i10-index

Created by Google Scholar and used in Google's My Citations feature. 

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

This very simple measure is only used by Google Scholar, and is another way to help gauge the productivity of a scholar.  

Advantages of i10-Index

  • Very simple and straightforward to calculate
  • My Citations in Google Scholar is free and easy to use

Disadvantages of i10-Index

  • Used only in Google Scholar

Publish or Perish (PoP) - A DIY Approach

Calculate your own h-index and other author indexes - It is a free software program that can be download onto a computer. It designed to help researchers manipulate Google Scholar citations to create their databases of citations from which they can generate their own metrics.  

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