Beyond the contribution that the Plan S can be expected to make to the adoption of transformative Open Access agreements by libraries and publishers alike, as the article by Bianco and Patrizii (2020, p. 60) shows, it is notable that it can be considered as a market intervention. Yet this article also clearly indicates that between 2012 and 2016 the model that has apparently led to the most significant reduction in the market share of closed-access journals is that of hybrid Open Access, which grew from 36.2% to 45% over this period, whereas the share of journals based on subscriptions only has declined by about 11 percentage points from 49.2% to 37.7%, in a near perfect illustration of a zero-sum game. By contrast, apparently Gold Open Access journals, based on article processing charges, have only grown from 12.4% in 2012 to 15.2% in 2016. In other words, to the extent that Open Access stands for the reduction in barriers to existing knowledge, for the period the model that has made the greatest contribution to the achievement of this goal is hybrid Open Access. From the market failure perspective, this model may also be called the most efficient for this period. Yet as the chart of Bianco and Patrizii (2020, p. 62) also demonstrates, for research libraries serial, i.e., journal, subscription costs have been projected to be the fastest growing expense category for this period and thereafter, which is likely interrelated with the interest in the Plan S whose membership primarily draws on third-party funders and charitable trusts. Therefore, while the Plan S can be expected to assist the university libraries to cope with existing and future budget limitations, such as by promoting specific Open Access models, its implications for the publishing market remain to be discovered.

As the articles collected in the volume Open Access and the Library, which Anja Oberländer and Torsten Reimer have edited, indicate, the earliest preprint servers date to the early 1990s, which predates the mainstream use of computers, e-mail and the Internet. At the same time, the Covid-19 crisis has pushed medical, health and biological science preprint services, such as bioRxiv and medRxiv, into the media limelight and scholarly focus. Both the earliest uses of preprints, such as arXiv, and the more recent ones have been driven by the need to promote the rapid dissemination of scholarly findings. What apparently distinguishes newer preprint servers, such as medRxiv, is the additional discovery- and attribution-oriented digital tools that they offer.The urgency of the coronavirus crisis has also apparently driven collaborations with Open Access journal publishers, such as PLOS, for topical conversations, expert discussions and project crowdsourcing. The newer slate of preprint servers also not infrequently have backing from charitable or non-profit foundations, such as the Wellcome Trust or Chan Zuckerberg Initiative, which distinguishes these from earlier generation servers, primarily supported by research institutes, e.g., the CERN. The main implication of this is the likely instability of preprint server funding, despite the important functions they perform.Similarly, successful preprint models appear to be bound to specific fields of inquiry or disciplines, e.g., particle physics, so that preconditions for launching and maintaining preprint servers for other research areas, such as humanities or social sciences, are not necessarily present.  The same may also apply to information distribution and discovery channels for digital collections, which may need to depend on libraries or joint initiatives, to become established.