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Author Impact Metrics
An author's impact on their field or discipline has traditionally been measured using the number of times their academic publications are cited by other researchers. There are numerous algorithms that account for such things as the recency of the publication, or poorly or highly cited papers. While citation metrics may reflect the impact or research in a field, there a many potential biases with these measurements and they should be used with care.
What is the h-index?
h-index, proposed by J.E. Hirsch in a 2005 article, is the most widely used research metric. It measures the productivity and impact of an author's scholarly output. Tools for calculating your h-index include Web of Science and Google Scholar.
- h-index = h has at least h papers that have been cited h times.
- For example, a researcher with an h-index of 22 has 22 papers that have been cited at least 22 times.
Advantages of the h-index
- The h-index looks at the cumulative impact of an author's scholarly output and performance. It measures quantity with quality by comparing publications to citations.
- Several resources, such as Web of Science and Google Scholar, automatically calculate the h-index as a part of citation reports for authors.
Disadvantages of the h-index
- h-index does not account for the number of authors per article; articles with many authors count the same as articles with just few or one. Nor does it account for the placement of the author.
- The metric is biased against "early-career" researchers that have fewer publications.
- Self-citations can skew results.
- Hirsch JE. An index to quantify an individual’s scientific research output. Proceedings of the National Academy of Sciences of the United States of America. 2005;102(46):16569-16572. doi:10.1073/pnas.0507655102.
What is the g-index?
g-index, proposed by Leo Egghe in his paper Theory and practice of the g-index, 2006, as an improvement to the h-index. The g-index gives more weight to highly-cited articles.
To calculate the g-index:
- "[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."
Advantages of the g-index
- Accounts for the performance of author's top articles.
- Helps to make more apparent the difference between authors' respective impacts. The inflated vales of the g-index help to give credit to lowly-cited or non-cited papers while giving credit for highly cited papers.
Disadvantages of the g-index
- Introduced in 2007, and the debate continues whether the g-index is superior to the h-index. It is not as widely accepted as the h-index.
The i10-index, a metric used by Google Scholar, is the number of publications with at least 10 citations for all of the citations listed in your profile. This is a very simple metric to calculate but it is only available in Google Scholar.
In the example below, the Google Scholar profile page shows both the h-index and i10-index.