The Issue with Special Issues: when Guest Editors Publish in Support of Self
The recent exceptional growth in special issues has led to the largest delegation of editorial power in the history of scientific publishing. Has this power been used responsibly? We provide the first systematic analysis of endogeny, the practice of publishing articles in ones own special issue. While moderate levels of endogeny are common, excessive endogeny constitutes scientific misconduct, as it stems from a clear conflict of interest. We define special issues containing more than 33% endogeny as SI-hacked. We build a dataset of over 100,000 special issues published in 2015-2025 by five leading publishers. The large majority of guest editors engage in endogeny responsibly, if at all. Nonetheless, despite endogeny policies by publishers and indexers, SI-hacking is endemic. All journals heavily relying on special issues host SI-hacking; more than 1,000 hacked SIs are published each year, hosting tens of thousands of endogenous articles. Egregious SI-hacking is rare, editors exceeding endogeny thresholds mostly to the extent that publishers allow them to. This is not good news, as it reflects a widespread normalisation of guest editor conflicts of interests. Fortunately, SI-hacking can be solved by enforcing existing common sense policies. We provide data and analyses needed for indexers and regulators to act.