Re: Open Access does not increase citations for research articles from The Astrophysical Journal

From: Stevan Harnad <>
Date: Fri, 7 Sep 2007 22:27:13 +0100

On Fri, 7 Sep 2007, Michael Kurtz wrote:

> Posted today on arXiv:
> Open Access does not increase citations for research articles from The
> Astrophysical Journal
> Authors: Michael J. Kurtz
> <>, Edwin A.
> Henneken <>
> (Submitted on 6 Sep 2007)
> Abstract: We demonstrate conclusively that there is no "Open Access
> Advantage" for papers from the Astrophysical Journal. The two to one
> citation advantage enjoyed by papers deposited in the arXiv e-print
> server is due entirely to the nature and timing of the deposited
> papers. This may have implications for other disciplines.


            Stevan Harnad

Kurtz & Henneken's (2007) new result is very interesting. Earlier,
Kurtz et al. (2005) had shown that the lion's share of the citation
advantage of astrophysics papers self-archived as preprints in Arxiv
was caused by (1) Early Advantage (EA) (earlier citations for papers
self-archived earlier) and (2) Quality Bias (QB) (a self-selection bias
toward self-archiving higher quality papers) and not by (3) Open Access
(OA) itself (being freely accessible online to those who cannot afford
subscription-toll access).

Kurtz et al. explained their finding by suggesting that:

    "in a well funded field like astrophysics essentially everyone
    who is in a position to write research articles has full access to
    the literature."

This seems like a perfectly reasonable explanation for their findings.
Where there is no access problem, OA cannot be the cause of whatever
higher citation count is observed for self-archived articles. Moed
(2007) has recently reported a similar result in Condensed Matter
Physics, and so have Davis & Fromerth in 4 mathematics journals.

Kurtz & Henneken's latest study confirms and strengthens their prior
finding: They compared citation counts for articles published in two
successive years of the Astrophysical Journal. For one of the years, the
journal was freely accessible to everyone; for the other it was only
accessible to subscribers. The citation counts for the self-archived
articles, as expected, were twice as high as for the non-self-archived
articles. They then compared the citation-counts for non-self-archived
articles in the free-access year and in the toll-access year, and found
no difference. They concluded, again, that OA does not cause increased

But of course K&H's prior explanation -- which is that there is no
access problem in astrophysics -- applies here too: It means that in a
field where there is no access problem, whatever citation advantage
comes from making an article OA by self-archiving cannot be an OA

K&H conclude: "This may have implications for other disciplines."

However, it should be evident that the degree to which this has
implications for other disciplines depends largely on the degree to which
it is true in other disciplines that "essentially everyone who is in a
position to write research articles has full access to the literature."

We (Hajjem & Harnad 2007) have conducted (and are currently replicating)
a similar study, but across the full spectrum of disciplines, measuring
the citation advantage for mandated and unmandated self-archiving for
articles from 4 Institutional Repositories that have self-archiving
mandates (three universities plus CERN), each compared to articles in
the very same journal and year by authors from other institutions (on
the assumption that mandated self-archiving should have less of a
self-selection quality bias than unmandated self-archiving).

We again confirmed the citation advantage for self-archiving, and found
no difference in the size of that advantage for mandated and unmandated
self-archiving. (The finding of an equally large self-archiving
advantage for mandated and unmandated self-archiving was also confirmed
for CERN, whose articles are all in physics -- although one could
perhaps argue that CERN articles enjoy a quality advantage over articles
from other institutions.)

A few closing points:

(1) It is likely that the size of the access problem differs from field
to field, and with it the size of the OA citation advantage. It is
unlikely that most fields are as well-heeled as astrophysics. In
Condensed Matter physics (and perhaps also mathematics) there is the
further complication that it is mostly just preprints that are being
self-archived, which reduces the scope for observing any postprint
advantage, as opposed to just an Early Advantage (EA). (In fields that
do have a significant access problem, the "Early Advantage" for
postprints is the OA Advantage!) OA self-archiving mandates (and the OA
movement in general) target refereed, accepted postprints, not
unrefereed preprints.

(2) The positive correlation is between citation counts and the number
of self-archived articles in each citation-range (Hajjem et al 2005).
This could be caused by Quality Bias (QA) (higher quality articles being
more likely to be self-archived) or Quality Advantage (QA) (higher
quality articles benefit more from being self-archived) or both.
(The top 50% of articles tend to be cited 10 times as often as the
bottom 50% [Seglen 1992]. This has nothing to do with OA or

(3) Citations are of course not the only potential advantage of
self-archiving. Downloads can increase too (Brody et al. 2006).

(4) We are now in the Institutional Repository (IR) era. Arxiv is a
venerable Central Repository, one of the biggest and oldest and most
successful of them all. But, institutions are the sources of OA content,
institutions are in the best position to mandate self-archiving, and
institutions share with their authors the benefits of enhancing the
accessibility, usage and impact of their research output. Moreover, the
nature of the web is distributed local websites, harvested by central
service providers, rather than central self-archiving.

Stevan Harnad

Brody, T., Harnad, S. and Carr, L. (2006) Earlier Web Usage Statistics
as Predictors of Later Citation Impact. Journal of the American
Association for Information Science and Technology (JASIST) 57(8)

Davis, P. M. and Fromerth, M. J. (2007) Does the arXiv lead to higher
citations and reduced publisher downloads for mathematics articles?
Scientometics, Vol. 71, No. 2.

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.

Hajjem, C. and Harnad, S. (2007) The Open Access Citation Advantage:
Quality Advantage Or Quality Bias? Technical Report, Electronics and
Computer Science, University of Southampton.

Kurtz, M. J. and Henneken, E. A. (2007) Open Access does not increase
citations for research articles from The Astrophysical Journal. Preprint
deposited in arXiv September 6, 2007.

Kurtz, M. J., Eichhorn, G., Accomazzi, A., Grant, C. S., Demleitner, M.,
Murray, S. S. (2005, "The Effect of Use and Access on Citations.
Information Processing and Management, 41, 1395-1402)

Moed, H. F. (2007) The effect of 'open access' on citation impact: An
analysis of ArXiv's condensed matter section, Journal of the American
Society for Information Science and Technology, August 30, 2007.

Seglen, P. O. (1992) The skewness of science. Journal of the American
Society for Information Science 43:628-38;2-0
Received on Fri Sep 07 2007 - 22:33:40 BST

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