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2 open-access publishers accused of excessive self-citation

Papers published by MDPI and Frontiers cite work from their journals at high rates, study finds

by Dalmeet Singh Chawla, special to C&EN
June 20, 2024 | A version of this story appeared in Volume 102, Issue 19


An illustration showing two hands pointing to each other against a background of paper files.
Credit: Madeline Monroe/C&EN/Shutterstock

Two big scholarly publishers of open-access research—meaning free to read outside a paywall—have been accused of excessively citing papers previously published in their own journals.

A study published in May before peer review on the preprint server SocArXiv suggests that high self-citation rates may have inflated the journal impact factor (JIF) of titles published by MDPI and Frontiers in recent years.

The study authors investigated the citation patterns of 8,360 journals published by 20 of the largest for-profit academic publishers from 1997 to 2021. They found that papers published by Frontiers and MDPI titles contain more self-citation than other publishers’ journals do.

Citations are important in academia because they are used to calculate metrics like the JIF, which is often incorrectly used to judge researchers and their work.

“The propensity to self-cite is pretty similar among all journals from all publishers except Frontiers and MDPI, which are two clear outliers,” says study coauthor Marco Seeber, a sociologist and public policy professor at the University of Agder. He notes that self-citation to studies published in the previous 5 calendar years, which are used to calculate the JIF, are particularly high.

It “is difficult to explain a concentration of citations within this window and across a publisher other than through manipulation,” says Matt Hodgkinson, a research integrity specialist and a member of the Committee on Publication Ethics who was not involved with the new study. “Clearly, perverse incentives are affecting citation behavior at a large scale,” he says, adding that the study is “well conceived and sophisticated.”

Previous research suggested that researchers in a dozen countries are citing their own papers at an unusually high rate, a phenomenon that the authors attributed to policies within those nations that incentivize such citation practices. In 2018, Seeber and colleagues reported that researchers in Italy increased their self-citation rates after a controversial 2010 law came into effect that required academics to meet certain productivity thresholds to be eligible for promotions.

Editors have been accused in the past of asking authors to add citations to previously published papers to artificially boost their journals’ citation metrics.

“Publishers and editors must never require or routinely ‘suggest’ that authors cite their journals in order that their articles be accepted,” Hodgkinson says. “[Even] if it were authors trying to curry favor and boost the [JIF] of their target journal, or editors going rogue, publishers still have a responsibility to oversee processes to ensure citations are not being manipulated.”

For him, it’s important that all citation-based metrics disregard or explicitly adjust for self-citation, whether it be by institution, editor, journal, or publisher. “Besides highlighting and policing citation manipulation, the wider solution is to stop evaluating authors and institutions based on the impact factor of the journals they publish in,” he says.

Giulia Stefenelli, chair of MDPI’s scientific board, says in an email that the publisher maintains a transparent policy on self-citation. “Any identified citation manipulation is closely monitored, and authors and reviewers are required to adhere to strict guidelines. Reviewers and academic editors are responsible for verifying the relevance of citations. MDPI does not, at any time, encourage the addition of journal citations to any article, as this would be unethical.”

A spokesperson for Frontiers says in an email that the study uses “unnecessarily convoluted methodology” to calculate self-citations and conflates the growth of publication output with self-citation. Our “Research Integrity Team has implemented specific checks to systematically monitor for unethical citation practices. Just as for all serious infringements, any reviewer or editor caught attempting such activity is subject to immediate dismissal,” the spokesperson says.


This story was updated on June 24, 2024, to correctly attribute the previous research suggesting that scientists in a dozen countries cite their own papers at an unusually high rate. It was not led by Marco Seeber but a different team.


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