Author Impact

An author's impact on their field or discipline has traditionally been meausred 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 of research in a field, there are many potential biases with these measurements and they should be used with care.  For a critique of author impact factors, see this article in the Chronicle of Higher Education.

Click on the links to learn more.

• H-Index

  The most widely used research metric, measures both productivity and impact of an author's scholarly output. Tools for calculating your H-index include Web of Science and Google Scholar.
• G-Index

  Proposed in 2006 by Leo Egghe as an alternative to the H-index, adds more weight to highly cited articles.
• i10-Index

  A very simple measure of impact, this metric is only used by Google Scholar.

The Web of Science uses the H-Index to quantify research output by measuring author productivity and impact.

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

Example: a scientist with an H-Index of 37 has 37 papers cited at least 37 times.  

Advantages of the H-Index:

• Allows for direct comparisons within disciplines
• Measures quantity and impact by a single value.

Disadvantages of the H-Index:

• Does not give an accurate measure for early-career researchers
• Calculated by using only articles that are indexed in Web of Science.  If a researcher publishes an article in a journal that is not indexed by Web of Science, the article as well as any citations to it will not be included in the H-Index calculation.

Tools for measuring H-Index:

• Web of Science
• Google Scholar

The G-index was proposed by Leo Egghe in his paper "Theory and Practice of the G-Index" in 2006 as an improvement on the H-Index.  

G-Index is calculated this way: "[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 g^2 citations." (from Harzig's Publish or Perish Manual)

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 values 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 2006. and debate continues whether G-Index is superior to H-Index.  Might not be as widely accepted as H-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

Here is a screenshot of a Google Scholar My Citations page for Charles Darwin (you can see the i10-Index highlighted in the small table):

Reference

http://guides.library.cornell.edu/c.php?g=32272&p=203393