Re: Does the arXiv lead to higher citations and reduced publisher downloads?

[Phil Davis <pmd8@cornell.edu>]

Kristin Antelman wrote:

> Data I collected for philosophy, political science, engineering 
> and mathematics do not support this hypothesis that OA causes 
> more citations for better articles only (given that one uses 
> overall citations as a rough measure of quality).
The data that Kristin illustrates do not show causation, only 
association.  Articles available freely from repositories are 
associated with a higher frequency of citations.  I have no 
contention with this claim, and everyone since Steve Lawrence 
(Nature, 2001) has backed this observation.  What I am arguing, 
however, is that the likely (and primary) cause of the citation 
advantage is not increased access, but some quality differential, 
leading to better articles being deposited in the arXiv.  In our 
manuscript, we argue that if OA-as-cause is present, its scope is 
severely limited to highly-cited articles.  How can we say this?

If increased access was the cause of increased citations in our 
data, we should see a significant and positive correlation 
between fulltext article downloads from the arXiv and the number 
of citations an article receives.  The rationale is that article 
repositories increases readership, some of which leads to 
increased citations (this is the argument that SPARC, Harnad, 
Suber and others use to justify the use of archives).  Now please 
take a look at Figure 3 in our paper 
(http://arxiv.org/pdf/cs.DL/0603056).  Notice that this positive 
association only applies to highly-cited articles (note: the 
inverse log of 2.5 is about 316 downloads).

In order to argue for causation one must be able to describe and 
measure the mechanism by which the cause takes place.  Antelman 
(and others) demonstrate only the association between open access 
and citations, and infer that open access must be the cause.  In 
our paper, we test the Open Access postulate, the Early View 
postulate, and a Quality Differential postulate.  Of these three 
we feel that the Quality Differential is the strongest 
explanation for the data.  We do not rule out Open Access 
completely, but the data do suggest that if access is responsible 
for increased citations, this effect may only take place for 
already highly-cited articles.

--Phil Davis