Metrics: what do they measure?

We have been preparing to contribute to one of the Academic Development Directorate's sessions for researchers (Publishing from Mature Projects) and, as part of this, have been drawing together some of the different measures of publication impact and influence.  This is not a complete list, but a representation of some of the metrics out there.

H-Index

This is a measure an individual's citations, based upon how many of their publications have been cited multiple times.  An H-Index of 4 indicates that 4 of the researcher's publications have been cited at least 4 times.  An H-Index of 10 indicates that 10 of the researcher's publications have been cited at least 10 times.  For this reason, experienced researchers are much more likely to have a higher H-Index than those in their early career.  Services such as Google Scholar and Web of Science offer H-Index calculations, based on the data they hold.  For this reason, it is possible to get different H-Index measures for the same researcher, dependent upon the tool used to calculate it. Find out more on Wikipedia.

Impact Factor

Perhaps the best known of the research metrics, this measures the 'impact' of a journal title.  This is produced by a commercial company, Thomson Reuters, based on their data.  For this reason, to access the full list of factors, a subscription fee must be paid (generally individual ones are available on the journal's website and can be found with a quick Google).  It is worked out from two years' worth of data, by dividing the number of times that articles in that journal title were cited in indexed research titles by the total number of articles published in the journal during the same period.  Again, there are varying critiques of this measure.

Altmetrics

Altmetrics have grown as a complementary measure to the more traditional ones and generally measure at the level of the individual research output (journal article, book chapter, data set...).  Rather than focusing upon counting citations in traditional research publications, these also include mentions on social media, inclusion on news sites, articles picked up by blogs, and use by researchers (via the Mendeley service), amongst many other outlets.  There is more information on Altmetric, the main service provider, on the ILS website.

To find out more, contact a member of the Academic Services Team in ILS and we will be happy to work with you.