Open Access Speeds Use by Others

Stevan Harnad harnad at ECS.SOTON.AC.UK
Tue May 16 10:14:58 EDT 2006

On Tue, 16 May 2006, Chuck Hamacker wrote:

> Chronicle of Higher Education=20

I've sent the following to CHE:

    The Eysenbach study is certainly not "the first to compare open-access
    and non-open-access papers from the same journal." See the growing
    bibliography of studies on the open-access citation advantage:

    Other studies listed there will also give CHE readers a better idea
    of whether it is indeed "[n]ot yet clear? whether the open-access
    advantage increases citation in the long run or whether the trend
    is similar for other journals."

and the following to PLoS:


            Stevan Harnad

I applaud and welcome the results of the Eysenbach (2006)
study on 1492 articles published during one 6-month period in one journal
(PNAS), showing that the Open Access (OA) articles were more cited than
the non-OA ones. I also agree fully that the findings are unlikely to
have been an artifact of PLoS's "strong and vested interest in publishing
results that so obviously endorse our existence," nor of the fact that
"the author of the article is also an editor of an open-access journal"
(all quotes are from the PloS editorial by MacCallum & Parthasarthy, 2006).

However, I am less sure that PloS's and the author's vested interests
are not behind statements (in both the accompanying editorial and the
article itself) along the lines that: "solid evidence to support or
refute" that papers freely available in a journal will be more often
read and cited than those behind a subscription barrier... has been
surprisingly hard to find." The online bibliography 'The effect of open
access and downloads ('hits') on citation impact' records a growing number
of studies reporting precisely such evidence as of 2001, including
studies based on data from much larger samples of journals, disciplines
and years than the PloS study on PNAS, and they all find exactly the
same effect: freely available articles are read and cited more.

There can be disagreement about what evidence one counts as "solid," but
there can be little dispute that prior evidence derived from
substantially larger and broader-based samples showing substantially the
same outcome can hardly be described as "surprisingly hard to find."

In fact, the only new knowledge from this small, journal-specific sample
was (1) the welcome finding of how early the OA advantage can manifest
itself, plus (2) some less clear findings about differences between
first- and last-author OA practices, plus (3) a controversial finding
that will most definitely need to be replicated on far larger samples in
order to be credible: "The analysis revealed that self-archived articles
are also cited less often than OA articles from the same journal."

The latter (3) is a within-journal (one journal, PNAS) finding; the
overwhelming majority of self-archived articles today (on which the
prior large-sample OA citation advantage findings are based) do not
appear in journals with a paid-OA option. Hence on the present evidence
I have great difficulty in seeing this secondary advantage as any more
than a paid-OA publisher's pipe-dream at this point.

The following, however, is not a pipe-dream, but a peccadillo: "no other
study has compared OA and non-OA articles from the same journal." To be
fair, this observation is hedged with "[a]s far as we are aware" (but
the OA-advantage bibliography is surely public knowledge -- or should be
among advocates of public access to science) and the observation is
further qualified with: "and [also] controlled for so many potentially
confounding factors."

But it has to be stated that of these "potentially confounding" variables
-- "number of days since publication, number of authors, article
type, country of the corresponding author, funding type, subject area,
submission track (PNAS has three different ways that authors can submit
a paper)... previous citation record of the first and last authors...
[and] whether authors choosing the OA option in PNAS chose to do so for
only their most important research (they didn't)" -- many are peculiar to
this particular short-interval, 3-option, single-journal PloS study. And
several of them (country, subject, year) had already been analyzed in
papers that had been published before this 2006 article and were not
taken into account despite the fact that both their preprints and their
postprints had been freely accessible since well before publication, and
that at least one of them (Brody et al. 2005) had been explicitly drawn
to the author's attention based on a preprint draft well before the
article was submitted to PloS.

Brody et al. (2005) had found that, alongside the OA citation advantage,
more downloads in the first six months after publication are correlated
with more citations 18 months later in physics; and Hajjem et al. (2005)
had found higher citations for OA articles within the same journal/year
for 1,307,038 articles published across 12 years (1992-2003) in 10
disciplines (Biology, Psychology, Sociology, Health, Political Science,
Economics, Education, Law, Business, Management).


Brody, T., Harnad, S. and Carr, L. (2005) Earlier Web Usage Statistics
as Predictors of Later Citation Impact. Journal of the American
Association for Information Science and Technology (JASIST) 56.

Eysenbach, G, (2006) Citation Advantage of Open Access Articles. PLoS
Biology 4(5)

Hajjem, C., Harnad, S. and Gingras, Y. (2005) Ten-Year
Cross-Disciplinary Comparison of the Growth of Open Access and How it
Increases Research Citation Impact. IEEE Data Engineering Bulletin 28(4)
pp. 39-47.

MacCallum, C.J., and Parthasarathy, H. (2006) Open Access Increases
Citation Rate. PLoS Biology 4(5)

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