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University Library, University of Illinois at Urbana-Champaign

Understanding Impact: Impact Factor and Other Research Metrics

This LibGuide will help you identify standard research metrics that are used to measure scholarly impact. This guide also outlines methods and tools you can use to identify journals in your field for publishing.

What are the different metrics?

Scholars have combined standard research metrics, like scholarly output and citation counts, into formulas to measure and assess author and journal impact in new ways. Some of these metrics include:

  • Journal Impact Factor
  • h-index
  • g-index
  • Eigenfactor score
  • Altmetric

On this page you will learn what these metrics measure, how to calculate these metrics, and databases and resources to look up each metric in.

Calculating bibliometrics

Calculating metrics can sometimes be complicated and confusing. This table provides a brief introduction to each calculation and what it means.

Metric

Website

Calculation

Meaning

 

 

 

 

Impact Factor

 

 

 

 

Journal Citation Reports

Use a two-year period to divide the number of times articles were cited by the number of articles that were published

Example:

200 = the number of times articles published in 2008 and 2009 were cited by indexed journals during 2010.

73 = the total number of "citable items" published in 2008 and 2009.

200/73 = 2.73

2010 impact factor

 

 

 

 

Impact factor reflects only on how many citations on a specific journal there are (on average). A journal with a high impact factor has articles that are cited often.

 

 

 

 

 

h-index

 

 

 

 

Web of Science, Google Scholar, Scopus

1) Create a list of all of your publications. Put the list in descending order based on the number of times it was cited (you can get this information from any of the sources to the left). The first article should have the most citations. Go through and number these.

2) Look down through the list to figure out at what point the number of times a publication has been cited is equal to or larger than the line (or paper) number of the publication.

Example:

Paper Number            # of citations

1                                 13

2                                   7

3                                    4

h-index= 3

*please remember that many databases will give you this number; this is only if you'd like to calculate it manually. You can also often find calculators online.

 

 

 

 

 

The h-index focuses more specifically on the impact of only one scholar instead of an entire journal. The higher the h-index, the more scholarly output a researcher has.

 

 

 

g-index

 

 

Harzing's Publish or Perish

 

 

Given a list of articles ranked in decreasing order of the number citations that they received, the g-index is the largest unique number to the extent that the top g articles received together is at least g2 citations.

The g-index can be thought of as a continuation of the h-index. The difference is that this index puts more weight on highly-cited citations. The g-index was created because scholars noticed that h-index ignores the number of citations to each individual article beyond what is needed to achieve a certain h-index. This number often complements the h-index and isn't necessarily a replacement.

 

 

 

Eigenfactor score

 

 

 

Eigenfactor.org

The Eigenfactor score is calculated by eigenfactor.org. However, their process is very similar to calculating impact factor and they pull their data from the JCR as well. The major difference is that the Eigenfactor score deletes references from one article in a journal to another in the same journal. This eliminates the problem of self-citing. The Eigenfactor score is also a five-year calculation. More information can be found through Journal Citation Reports.

 

A high Eigenfactor score signals that the journal does not self-cite and controls the network of that discipline. It's useful to look at scholar's h-index as well as the Eigenfactor score of the journals they publish in in order to get a broad sense of their impact as a researcher.

 

 

 

 

Altmetric

 

 

 

 

Altmetric.com

 

 

Altmetric scores are usually calculated by companies. This means that they can't be calculated manually. To see an explanation of how this metric is caculated, you can visit the Altmetric support page.

Different sources go into altmetrics calculations, depending on the company and the information that they are using. But in general, a high altmetric score indicates that an item has received a lot of attention and it has also received what that company has decided is "quality" attention (i.e. a news post might be more valuable than a twitter mention). Remember that attention doesn't necessarily indicate that the article is important or even of quality. That's why it's useful to use altmetrics and impact factor together.