At this point, it is important to highlight some key characteristics of the two main business models in the scientific publishing industry, and how these characteristics affect the behavior of authors, publishers, and journals’ editors.

In the traditional “subscription-based” business model, the revenues of the publishers derive from subscription fees paid by public librarie—typically university and institutional libraries. In this model the customer is the reader, and the reader’s goal is to access high-quality content. Therefore, if the publishers aim at increasing profits, they need to promote the quality of the journals. On their side, the editors of the journals are scientists, whose goal is to maximize their prestige and reputation, and they can achieve these goals by curating the quality of the content. In turn, this model creates an alignment of incentives towards quality and common interest in rigorous, selective peer review.

In the APC model, the revenues derive from authors who publish articles: in a way, the customer is the author itself. The authors’ goal is to publish, and the publishers’ profits depend on the volume of articles published: they both have a common interest in publishing articles in large numbers and in shortest times.

The different goals and interests for authors, editors, and publishers in the two business models is reflected in the journals’ acceptance rate, the turnaround time, i.e., the time elapsed from the submission of an article to its acceptance, special issues policies, and the journals’ growth rates. For example, the acceptance rate of journals owned from MDPI, the largest APC for-profit publisher, is two to three times higher than the acceptance rate of traditional publishers [16]. There are huge differences also regarding the turnaround time. Peer review is a time-consuming process, and the turnaround time in 2022 was estimated between 134 and 198 days on average for journals from the major traditional publishers and nonprofit OA publishers, which all experienced longer and longer turnaround times in recent years—among others, because of the increasing challenges in finding reviewers [17]. The picture is very different for journals owned by APC for-profit publishers, which display increasingly faster turnaround time, as evaluated for MDPI (37 days), Frontiers (72 days), and Hindawi (83 days) [16].

A major difference is also observed in the proportion of articles published via standard or special issues. Peer review in special issues can adhere to strict standards, and involve independent reviewers selected by the journal editors. In other cases, the peer review is managed by the guest editors, namely the scientists that promote the Special Issue, invite contributors, and very often publish themselves one or more articles in the Special Issue. In this latter situation, the special issues have pros and cons. On the one hand, from the journals’ point of view they kill two birds with one stone: they attract new submissions and reduce the costs by delegating the management of the peer review process to the guest editors. On the other hand, because of some intrinsic endogamy in the process, the peer review is often not so independent and rigorous as it is for standard submissions, thus entailing the risk of accepting below-average contributions. The extent of the use of special issues differs deeply among publishers, and in a way consistent with the respective goals. Special issue articles represent only a tiny fraction, namely below 5%, of the publications for traditional and nonprofit OA publishers’ journals. On the contrary, special issue publications represent the vast majority for the major for-profit APC publishers, in the order of 70–80% [16]. For example, in 2023, the International Journal of Molecular Sciences and Sustainability, i.e., the two largest MDPI journals, published each more than 3000 special issues, which means more than 9 per day.Footnote 4 Because of similar practices and traits, it is a debated question whether MDPI can be even considered as a predatory publisher [18].

Perhaps, the most remarkable difference between the two categories of journals consists in the different growth rates displayed in recent years, namely in the exponential growth of APC publishers compared with stable or slow growing trends for the other publishers. For example, MDPI grew from 17,000 publications in 2015 to 263,000 publications in 2022, becoming the second largest for-profit publisher in the world, surpassing Springer and second only to Elsevier. Such staggering growth is best illustrated by the complete reshuffling of the largest scientific journals that occurred in few years.

Figure 5 compares the 15 largest scientific journals by number of articles publishers in a year, respectively in 2010 and in 2022. In 2010, two of them (gray histograms in the figure) were nonprofit OA journals, including PLOS One, the most prolific journal, with 6700 articles published that year; the other 13 journals were subscription-based journals, 11 of which were owned by a learned society (striped histograms), and two by a for-profit publisher (black histograms). In 2022, all the 15 largest journals published more articles than the largest journal in 2010. All but three were gold open access journals controlled by for-profit publishers, of which ten were from fast growing APC publishers: MPDI (eight) and Frontiers (two).

Largest journals by number of articles published in 2010 and 2022—Source: Scopus-Scimago. Gray: nonprofit OA; striped: learned society, nonprofit, subscription/hybrid; black: for-profit subscription/hybrid; white: for-profit APC

A similar reshuffling has been observed also in the specific field of chemistryFootnote 5: in 2010, all the journals were controlled by publishers following a subscription-based business model, ten of them being owned by learned societies, including the largest one—Acta Crystallographica Section E, with 4000 articles—and five being from for-profit subscription-based publishers. In 2022, only three journals are controlled by learned societies, and 12 from for-profit publishers; the three largest journalsFootnote 6 were all controlled by MDPI, and published, respectively, 16,000 10,000 and 9000 articles.

There is, of course, a tension between the goals of an APC for-profit publisher, whose profit depends on the quantity of articles published, and the scientific editors, who aim at improving their own reputation via quality and selectivity. Moreover, while the subscription-based business model guarantees a stable source of revenues, regardless of the publishing volumes, the APC business model requires journals to maintain large publishing volumes. Hence, editors pursuing quality via selectivity hinder the publishers’ goals, so that in for-profit APC journals the editors are often less experienced academics, or even nonacademics.

In turn, the for-profit APC model seems to fit well Christensen’s definition of disruptive innovations, namely innovations that make it much simpler and affordable to own and use a product for people who, historically, did not have the skills to be in the market [19, 20].Footnote 7 In this case, people that were not skilled enough to publish in the traditional system, now can, by paying… Disruptive innovations typically start in marginal market segments, so that dominant organizations need time before being able to realize how important they are [19]. But in this case, they eventually did, as APC turned to be a much more profitable business model than subscriptions fees, becoming increasingly popular also among traditional publishers [21].