PubMed Central (PMC) is by far the largest public repository of biomedical articles. This is made possible, in part, by federal mandates that require authors who received funding from the National Institutes of Health (NIH) to deposit copies of their final author manuscripts into the archive. The bulk of articles in PMC, however, are deposited by publishers on behalf of their authors.
Which leads us to wonder whether publishers, by depositing research articles into PMC, may be collectively creating an über publisher that is competing against them for readership of of their own articles.
Alternatively, PMC could be satisfying the needs of readers traditionally underserved by scientific journals. In this sense, PMC would be complementing publishers by increasing their scope of dissemination.
I was fortunate enough to work on a study recently that attempted to answer the question of whether PMC is complementing, or competing with, journal publishers. The article, “The Effect of Public Deposit of Scientific Articles on Readership” is published in the October issue of The Physiologist.
The study focuses on readership (as measured by full text HTML article downloads) for 3,499 articles published in 12 research journals published by the American Physiological Society (APS) between July 2008 and June 2009. Articles published in APS journals are available to subscribers for the first 12 months from final publication, after which they become freely available to all readers from the journals’ websites.
A total of 1,886 (or 54%) of these articles declared some form of NIH funding, were deposited by the publisher into PubMed Central, and were made freely available from PMC 12 months after final publication. These papers formed the treatment group — the treatment, in this case, being deposited into PMC.
Figure 1 describes how each of these groups performed over the first 24 months of publication.
After final publication, both treatment and control articles received about 85 downloads per article, on average, in their first month. Between months 1 and 12, treatment articles behaved similarly to control articles, which is to be expected, considering that treatment articles remained embargoed in PMC until month 13.
Between months 12 and 13, something dramatic took place. Control articles saw a major boost in full text downloads when they became freely available from the publishers site. Treatment articles also received a boost but the increase was about 14% smaller than control articles. Since the treatment articles were also freely available simultaneously from the journal websites, the reduction in reader traffic cannot be explained by differential access barriers. We are testing free against free.
Unless you can come up with an alternative explanation, it is pretty clear that PMC is responsible for that 14% reduction in usage statistics from the journal websites. The publisher isn’t trying to sell access to those articles — they are given away for free — but the publisher can report these statistics back to their subscribing institutions as evidence that their materials are being used and have value.
As librarians base cancellation decisions, in large part, on publisher-provided usage data, a significant reduction in usage data as a result of PubMed Central may have unintended consequences on those publishers who participate in the PMC direct article deposit program.
Business model aside, drawing readership away from the journal to a repository may have more serious long-term consequences for society and association-based publishers. When readers turn from a journal to a repository, the publisher may be unable to point readers to related articles, editorials, and commentary surrounding the article of interest. It may also represent a lost opportunity to deliver news, educational material, advertisements (job announcements, grant and travel opportunities, products and services), and society events (conferences and workshops) to the reader. In sum, the publisher loses some ability to create a community of interest surrounding the journal.
From a network science standpoint, the discovery that PubMed Central has a negative effect on publisher-side article downloads should not be surprising. Google favors large, interlinked nodes in its search results, and readers searching PubMed would view the abstract with a FREE icon pointing them to the PMC article version. (Some publishers feel strongly that PubMed preferentially promotes the PMC copy over the journal copy.)
This first study of the effect of public deposit of NIH-sponsored articles in PubMed Central strongly suggests that PubMed Central is competing, in part, with journal publishers for readers of the scientific literature. It does not answer:
- Whether the results of physiology journals are generalizable to other disciplines
- Whether public access reduces PDF views in the same way as full text (HTML) views
- Whether final author manuscripts are a substitute for the final published article
- Whether the effect of PMC is growing as the repository increases in size
In the next few months, I hope to answer these questions as well.