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The slowing down of the biggest scientific journal

PLoS ONE started 11 years ago to disruptively change scholarly publishing. By now it is the biggest scientific journal out there. Why has it become so slow?

Many things changed at PLoS ONE over the years, reflecting general trends in how researchers publish their work. For one thing, PLoS ONE grew enourmously. After publishing only 137 articles in its first year, the number of articles published per year peaked in 2013 at 31,522.

plos-one_publication-count-per-year

However, as shown in the figure above, since then they have declined by nearly a third. In 2016 only 21,655 articles were published in PLoS ONE. The decline could be due to a novel open data policy implemented in March 2014, a slight increase in the cost to publish in October 2015, or a generally more crowded market place for open access mega journals like PloS ONE (Wakeling et al., 2016).

However, it might also be that authors are becoming annoyed with PLoS ONE for getting slower. In its first year, it took 95 days on average to get an article from submission to publication in PLoS ONE. In 2016 it took a full 172 days. This renders PLoS ONE no longer the fastest journal published by PLoS, a title it held for nine years.

plos-one-rev-time-versus-other-journals-rev-time

The graph below shows the developemtn of PLoS ONE in more detail by plotting each article’s review and publication speed against its publication date, i.e. each blue dot represents one of the 159,000 PLoS ONE articles.

plos-one-is-getting-slower

What can explain the increasingly poor publication speed of PLoS ONE? Most people might think it is the sheer volume of manuscripts the journal has to process. Processing more articles might simply slow a journal down. However, this slow down continued until  2015, i.e. beyond the peak in publication output in 2013. Below, I show a more thorough analysis which reiterates this point. The plot shows each article in PLoS ONE in terms of its time from submission to publication and the number of articles published around the same time (30 days before and after). There is a link, for sure (Pearson r = .13, Spearman rho = .15), but it is much weaker than I would have thought.

plos-one_output-competition-versus-speed

Moreover, when controlling for publication date via a partial correlation, the pattern above becomes much weaker (partial Pearson r = .05, partial Spearman rho = .11). This suggests that much of PLoS ONE’s slow down is simply due to the passage of time. Perhaps, during this time scientific articles changed, requiring a longer time to evaluate whether they are suitable for the journal.

For example, it might be that articles these days include more information which takes longer to be assessed by scientific peers. More information could be mirrored in three values: the number of authors (information contributors), the reference count (information links), the page count (space for information). However, the number of authors per article has not changed over the years (Pearson r = .01, Spearman rho = .02). Similarly, there is no increase in the length of the reference sections over the years (r = .01; rho = -.00). Finally, while articles have indeed become longer in terms of page count (see graph below), the change is probably just due to a new lay-out in January 2015.

plos-one-is-getting-longer

Perhaps, it takes longer to go through peer-review at PLoS ONE these days because modern articles are increasingly complex and interdisciplinary. A very small but reliable correlation between subject categories per article and publication date supports this possibility somewhat, see below. It is possible that PLoS ONE simply finds it increasingly difficult to look for the right experts to assess the scientific validity of an article because articles have become more difficult to pin down in terms of the expertise they require.

plos-one-is-getting-a-tiny-bit-more-interdisciplinary

Having celebrated its 10 year anniversary, PLoS ONE can be proud to have revolutionized scholarly publishing. However, whether PLoS ONE itself will survive in the new publishing environment it helped to create remains to be seen. The slowing down of its publication process is certainly a sign that PLoS ONE needs to up its game in order to remain competitive.

Wanna explore the data set yourself? I made a web-app which you can use in RStudio or in your web browser. Have fun with it and tell me what you find.

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Wakeling S, Willett P, Creaser C, Fry J, Pinfield S, & Spezi V (2016). Open-Access Mega-Journals: A Bibliometric Profile. PloS one, 11 (11) PMID: 27861511

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