The lowdown on self-citations

Self-citations are often a point of discussion when it comes to ranking season, and never more than this year when, for the first time, we have had access to the necessary data to be able to remove self-citations from our consideration thanks to additional data supplied by Elsevier from Scopus this year, but what does that really mean?

Simply put, a self-citation is an author citing their own previous work. Many leading academics may have every reason to do so having been responsible for some of the seminal works in their field, other academics may engineer opportunity to do so in order to influence their personal h-index or their institutional metrics. Either way, self-citations are a fact of life and can potentially be used contructively to trach threads of research and map academic careers.

As with many things there are a number of different ways the impact of self-citations can be viewed:

• Of all of the institutions we looked at the institution with the largest absolute number of self-citations, by some margin, is Harvard with over 93,000 representing 12.9% of their overall citations count
• The top five institutions producing over 3,000 papers, in terms of proportion of self-citations are all in Eastern Europe - St Petersburg State University, Czech Technical University, Warsaw University of Technology, Babes-Bolyai University and Lomonosov Moscow State University
• The top five in terms of the difference in citations per paper when self-citations are excluded are Caltech, Rockefeller, UC Santa Cruz, ENS Lyon and the University of Hawaii
• And the top 10 in terms of the difference in citations per faculty when self-citations are included are:

#InstitutionCountry1California Institute of Technology (Caltech)United States2Rockefeller UniversityUnited States3Stanford UniversityUnited States4Gwangju Institute of Science and Technology (GIST)South Korea5Karolinska InstituteUnited States6Princeton UniversityUnited States7Leiden UniversityNetherlands8Harvard UniversityUnited States9University of California, San Diego (UCSD)United States10University of California, San Francisco (UCSF)United States

Caltech have been perennially number one, amongst institutions featured in the main ranking, for this indicator and nothing has changed this year, although due to the impact of removing self-citations the gap has closed somewhat in the underlying ratios and for some institutions further down the tables, this revision in the methodology may be felt more keenly.