Citation metrics are methods to quantify academic output and impact within that particular field. Generally, metrics are not advised for comparison across disciplines because each discipline has it's own citation practices and norms for turn around time and amount of citations. None of these methods for quantifying value is perfect and each has its own advantages and disadvantages. Some faculty groups look to citation metrics as an element for promotion. This page will seek to introduce you to some common metrics.
H-Index - The H-Index aims to quantify a scholar’s impact over time while accounting for outlying papers which may produce a high amount of citations not necessarily reflective of the scholar's output and impact over time. The calculation for H-impact is the number of articles you’ve published that produce at least as many citations. It was proposed by J.E. Hirsch in a 2005 article in PNAS.
What's My Metric?
Web of Science also has tools allowing you to find the H-Index of a scholar.
**If the numbers from WOS and Google Scholar aren’t the same for a single scholar, don’t worry. The variance is easily explained by the fact that WOS is examining a highly curated list of journals. Because Google Scholar contains much more content such as a wider array of journals, grey literature, conference proceedings and more, Google Scholar is expected to list a slightly different number.
Calculating the H-Index for Harriet J. Numbers. Note that Harriet J. Numbers is a fictitious author created for exemplifying metrics.
Harriet J Numbers has published 9 journal articles so far in her career. Of the 9 journal articles, the citation count is currently:
Harriet J Numbers currently has an H-Index of 6 because she has at least 6 papers with a citation count of 6 or more.
H5-Index - The H5-Index is the H-Index but within the last 5 years. While the H-Index was originally intended to be an author level metric, the H-Index and the H5-Index are also used for journals. Google Scholar maintains a list of the top journals by H5-Index median and H5-Index. Click here for a list from Google Scholar under the category Life Sciences & Earth Sciences.
What's My Metric?
You can calculate your own H5-Index.
Calculating the H5-Index for Harriet J. Numbers. Note that Harriet J. Numbers is a fictitious author created for exemplifying metrics.
Harriet J Numbers has published 9 journal articles so far in her career. Of the 9 journal articles, the citation count is currently:
Harriet J Numbers currently has an H5-Index of 5 because she has at least 5 papers with a citation count of 5 or more were published within the last 5 years. This calculation includes 2015-2019.
Eigenfactor - The Eigenfactor is a journal-level metric designed to measure the number of citations garnered from a journal in addition to the source quality and reputation. It examines the past 5 years of activity, citation from a highly regarded journal like Nature would be ranked slightly higher than a citation from the Journal of Evolutionary Biology. The metric was developed as a collaboration between Carl Bergstrom and Jevin West at the University of Washington in 2007. The Eigenfactor seeks to take into account the broader network of impact rather than simply the immediate citation count. The size of a journal will directly impact the Eigenfactor. For example, if an article increases article output significantly, it's Eigenfactor will rise. The sum of all Eigenfactors totals 100 in each category. There are many Eigenfactor categories. Thus, the vast majority of Eigenfactor scores are less than 1.
What's the Metric?
The Journal Impact Factor was conceptualized by Eugene Garfield for the Institute for Scientific Information or ISI. As the name suggests, this is a journal-level metric, looking at the number of citations a journal is able to garner over a specific time span. The metric has a simple calculation and is searchable by journal (title or ISSN) in the Journal Citation Reports accessible through the Web of Science Database.
What's the Metric?
Calculation:
Each journal that is indexed by Web of Science (formerly ISI) receives a new Journal Impact Factor (JIF) each year. The calculation of the metric is based on the number of citations that the journal has produced over the course of the year for articles published in the prior two years. To calculate this metric, take the past three years of publication in a journal. Enumerate all of the citations that occurred in the third year for articles published in years one and two, divide the total by the sum of all citable items from the first two years and you have your impact factor for the third year.
Example:
I want to calculate the 2018 Journal Impact Factor for the publication Proceedings of Fake. I need to take the number of citations that occurred in 2018 referencing articles published in 2016 - 2017. Once I have that number I divide by the total number of citable items that occurred in 2016 - 2017.
Altmetrics is short for "alternative metrics." This metric is for calculating a number for individual journal articles or published datasets. This metric is designed to take into account activity and interest surrounding a publication. Some examples of this interest and activity might be a share on social media, citation on Wikipedia, reference manager use, a blog post mention, mainstream news reporting and more. Altmetrics gathers all of this activity and formulates it into a number. The basic idea is that Altmetrics are capturing activity that is an alternative to more traditional methods like counting citations or measuring journal prestige.
What's the Metric?
Unfortunately, there is no breakdown as to the precise calculations that go into this metric. It's based on an algorithm that is fed by internet traffic and activity. But, if you have an article in mind, it's pretty easy to track down.
You can add an Altmetrics bookmarklet to your browser bookmark bar at no cost as an individual researcher. You do have to provide some information to access the bookmarklet, like name and institution. Download it: https://www.altmetric.com/products/free-tools/
Once you have it loaded, just navigate to an article and click the bookmarklet.
Note of caution: once a metric is out there, it's bound to be misused as well as used appropriately. Many of the metrics mentioned above can be manipulated to make research output at the journal level or author level look better.
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