Sadly I couldn’t find much on the perception of non-academics of open-access mega journals, which is an important consideration for e.g. graduate students who do not want to pursue a career in academia.

The TL;DR of these notes is something like:

  • It’s hard to generalise about publishers or about publishing models
  • There’s good reason to steer clear of MDPI, but other open-access publishers seem fine

Holmberg et al 2019, Do articles in open access journals have more frequent altmetric activity than articles in subscription‑based journals? An investigation of the research output of Finnish universities

  • “The results show signifcant disciplinary and platform specifc diferences in the OA advantage, with articles in OA journals within for instance veterinary sciences, social and economic geography and psychology receiving more citations and attention on social media platforms, while the opposite was found for articles in OA journals within medicine and health sciences. The results strongly support feld- and platform-specifc considerations when assessing the infuence of journal OA status on altmetrics.”

Langham-Putrow et al 2021, Is the open access citation advantage real? A systematic review of the citation of open access and subscription-based articles

  • “Over the last two decades, the existence of an open access citation advantage (OACA)— increased citation of articles made available open access (OA)—has been the topic of much discussion. While there has been substantial research to address this question, findings have been contradictory and inconclusive. We conducted a systematic review to compare studies of citations to OA and non-OA articles.”
  • “64 studies (47.8%) confirmed the existence of OACA, while 37 (27.6%) found that it did not exist, 32 (23.9%) found OACA only in subsets of their sample, and 1 study (0.8%) was inconclusive. Studies with a focus on multiple disciplines were significantly positively associated with finding that OACA exists in subsets, and are less associated with finding that OACA did not exist.”

Ionnidis et al 2023, The Rapid Growth of Mega-Journals: Threats and Opportunities

  • “Journals are not permanent: of 27 general medical journals publishing in 1959, only 6 published continuously with the same name until 2009. The half-lives of scientific journals may be shortened in the current shifting environment. What matters is whether journals that publish the lion’s share of the literature endorse and facilitate the best research practices.”

Kim and Atteraya 2023, A decade of changes in OA and non-OA journal publication and production

  • “(a) although the number of OA journals has increased rapidly between 2011 and 2021, their share of total publications is still significantly lower than that of non-OA journals; (b) between 2011 and 2021, the number of publishers of non-OA journals had decreased slightly, while the number of OA journal publishers has increased rapidly; (c) publishers of all sizes increased the production of OA journal articles between 2011 and 2021, but the share of top publishers increased the most; and (d) MDPI, as a born-OA publisher, has become a global leader in OA journal article publishing in recent years.”
  • “The rapid increase in the number of OA journals between 2011 and 2021 has not translated to a proportionate increase in their share of total publications. This suggests that adoption of OA publishing still faces barriers, and non-OA publishers remain dominant. The study suggests that most top publishers have adapted successfully to the new publishing environment, with many traditional publishers offering both OA and non-OA journals as a result of the OA movement.”
  • “It has been argued that megajournals may have lost momentum as publishing models have matured (Brainard, 2019). However, the growth of MDPI and Frontiers Media shows otherwise, as they have not yet reached their peak in journal article publishing. The journal publishing industry will likely continue to undergo changes in the near future. According to Zhang et al. (2022), major publishers have been considering launching their own megajournals in order to publish large numbers of research papers per month. Although the total number of articles is an important metric for measuring publisher performance, asset risks differ significantly between traditional and megajournal publishers. Publishers of megajournals are not equally regarded as publishers of traditional non-OA journals by peers in their scientific field. Publishers of megajournals generally publish less prestigious journals than those published by traditional publishers, although their acceptance rate has declined in recent years (Björk, 2021).”

M. Ángeles Oviedo-García 2021, Journal citation reports and the definition of a predatory journal: The case of the Multidisciplinary Digital Publishing Institute (MDPI)

  • “The Multidisciplinary Digital Publishing Institute (MDPI) had 53 journals ranked in the 2018 JCRs annual report. These journals are analysed, not only to contrast the formal criteria for the identification of predatory journals, but taking a step further, their background is also analysed with regard to self-citations and the source of those self-citations in 2018 and 2019.”
  • “As depicted in Figure 5, the impact factors of all journals were reduced when self-citations were removed. The drop in the impact factor ranged between 38.96% in the case of Sustainability to 0.68% in Medicina with an average reduction of 14.8% in the value of the journal impact factor following the removal of self-citations”
  • “According to Clarivate, self-citation in the WOS typically ranges from 0% to 15%”
  • (so MDPI as a whole seems to be within that typical range, though some specific journals may be much higher; but I think these methods are unfair and introduce bias against MDPI. That is, it might also be the case that other journals in Web of Science also have these high self-citation rates, because here the author has done a detailed analysis of MDPI journals but has done a very cursory summary of non-MDPI journals. Of course, if you look at every data point of group A but only a very general average of group B, you’re going to find numbers in A that are larger than the numbers you find in B.)
  • “It is well known that the direct relation between income and the number of manuscripts that are accepted prompts predatory journals to conduct cursory peer reviews, in such a way that the rejection rate is minimal, so that ample economic returns are still guaranteed (Beall, 2016; Frandsen, 2017). As Siler (2020) asserts ‘the subordination of professional logics to market logics is in clear breach of academic norms and indicative of an illegitimate academic niche’. The revision times of the 53 journals under analysis were surprisingly similar, regardless of the high variability of the articles published in each journal in 2019 and were, in many cases, very much shorter than time spans that may be considered normal. As such the question arises whether or not this speed is achieved with a thorough peer review in line with editorial and publishing best practices or if the rigor and quality of the peer review process is compromised in order to achieve these speeds.”
  • (I think this analysis is mostly just repeating existing criticisms of MDPI’s publishing model)

Csomós and Farkas 2022, Understanding the increasing market share of the academic publisher “Multidisciplinary Digital Publishing Institute” in the publication output of Central and Eastern European countries: a case study of Hungary

  • “Our results show that researchers generally consider MDPI journals’ sufciently prestigious, emphasizing the importance of the inclusion of MDPI journals in Scopus and Web of Science databases and their high ranks and impacts.”

Hanson et al 2024, The strain on scientific publishing

  • (this paper seems to apply equal rigour to different publishers and thus seems like a more rigorous version of the Oviedo-García 2021 paper above)
  • “Ultimately, the factor that best predicted rejection rates was the publisher itself: Although both Frontiers and MDPI have similar growth in special issue articles (Figure 2), they show opposite trends in rejection rates over time, and MDPI uniquely showed decreasing rates compared to other publishers (Figure 4A). Raw rejection rates for MDPI in 2022 were also lower than for other publishers.”
  • “In 2022, impact inflation in MDPI and Hindawi were significantly higher than all other publishers (padj < .05). Interestingly, Frontiers had low impact inflation comparable to other publishers, despite growth patterns similar to MDPI and Hindawi.”
  • “The reason behind MDPI’s anomalous impact inflation appears to be straightforward: MDPI journals nearly universally spiked in rates of articles citing other articles from the same journal during the study period (here referred to as “self-citation” rate, Figure S14B).”
  • “Throughout our study, MDPI was an outlier in every metric—often by wide margins. MDPI had the largest growth of indexed articles (+1,080%) and proportion of special issue articles (88%), shortest turnaround times (37 days), decreasing rejection rates (−8 percentage points), highest impact inflation (5.4), and the highest within-journal mean self-citation rate (9.5%).”
  • “Interestingly, Frontiers had low impact inflation comparable to other publishers, despite growth patterns similar to MDPI and Hindawi.”
  • “Our study shows that regulating behaviors cannot be done at the level of publishing business model. Gold open access, for example, does not necessarily add to strain, as gold open access publishers like PLOS (not-for-profit) and BMC (for-profit) show relatively normal metrics across the board.”