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:
What is citation analysis?
Citation analysis is the study of the impact and assumed quality of an article, an author or an institution based on the number of times works and/or authors have been cited by others.
Why use it?
♦ To find out how much impact a particular article has had, by showing which other authors based some work upon it or cited it as an example within their own papers.
♦ To determine how much impact a particular author has had by looking at his/her total number of citations.
♦ To find out more about a field or topic; i.e. by reading the papers that cite a seminal work in that area.
Source: Citation Analysis Guide from University of Michigan. Authors: Paul Grochowski, Barbara Shipman, Deirdre Spencer, Sue Wortman.
Metric
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Website |
Calculation |
Meaning |
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Impact Factor |
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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. |
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h-index |
Web of Science, Google Scholar, , or Harzing's Publish or Perish |
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. |
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g-index |
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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. |
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Eigenfactor score |
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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. |
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Altmetric |
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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. |