[Moderator's Note: The research community may not yet have grasped
the significance of the dramatic causal connection between the
number of times a paper is accessed and the number of times it is
later cited. Tim Brody's remarkable download/citation correlator
http://citebase.eprints.org/analysis/correlation.php is able to
predict from download counts what the citation counts will be 6-24
months later. This kind of early-days predictor could add a new
dimension to scientometric evaluation of performance. It also strongly
corroborates Michael Kurtz's "rule of 17" in astrophysics: 17 "reads"
generates 1 "cite." It follows that whatever multiple of 17 reads is
lost because of access-denial, that is also the number of citations
lost! -- Stevan Harnad]
http://www.ecs.soton.ac.uk/~harnad/Temp/self-archiving_files/Slide0025.gif
Dear Stevan,
The "rule of 17" is the observation
-- from
http://cfa-www.harvard.edu/~kurtz/jasist2-abstract.html --
that the Astrophysics Data System (ADS)
http://adswww.harvard.edu/
ratio of "reads" to "cites" is about 17/1 for papers of the same age,
once a few years have past since publication. Because for these papers
ADS is the predominant means of reading them (about 90% I would guess),
this [correlation] seems to be a causal one.
For papers from the Astrophysical Journal, the reads/cites ratio is really
more like 12/1, but 17/1 may be correct for the related and secondary
literature which dominates the "missing reads."
Because citations scale exactly with reads (eqn 3 and fig 3 in the paper),
missing reads translate directly into missing cites. This different
from the [phenomenon] that preprinted articles are more frequently cited,
which is due in large part to the differing quality of preprinted vs
non-preprinted articles [i.e., preprinted ones are of higher quality]. In
1997, for example, 25% of articles from the Physical Review are in
the ArXiv (according to Tim Brody's data) but 4 of the top 5 and
7 of the top 10, ranked by number of citations, are in the ArXiv:
http://opcit.eprints.org/opcitresearch.shtml
For me the bottom line result of my little experiment is that even for
astronomy, with its near ideal [i.e., small, universally affordable]
toll-based system, fully 20% of all potential article reads are thwarted
by the access controls (and lack of electronic versions). (The fact that
many of the inaccessable papers are in the ArXiv probably does not change
this much, as the additional effort involved [from leaving ADS's unified
resource to go to another system] is a great deterrent.)
Cheers,
Michael
-------------
Michael Kurtz
Harvard-Smithsonian Center for Astrophysics
60 Garden Street
Cambridge, MA 02138
Received on Thu Apr 08 2004 - 23:25:43 BST
