[Hyperlinked version of this posting: http://openaccess.eprints.org/index.php?/archives/443-guid.html 
]

	Evans, James A. (2008) Electronic Publication and the Narrowing of  
Science and
	Scholarship Science 321(5887): 395-399 DOI:10.1126/science.1150473
	http://www.sciencemag.org/cgi/content/abstract/321/5887/395

	Excerpt: "[Based on] a database of 34 million articles, their  
citations (1945 to 2005),
	and online availability (1998 to 2005),... as more journal issues  
came online, the
	articles [cited] tended to be more recent, fewer journals and  
articles were cited,
	and more of those citations were to fewer journals and articles...  
[B]rowsing of print
	archives may have [led] scientists and scholars to [use more] past  
and present
	scholarship. Searching online... may accelerate consensus and narrow  
the range
	of findings and ideas built upon."

Evans found that as more and more journal issues are becoming  
accessible online (mostly only the older back-issues for free),  
journals are not being cited less overall, but citations are narrowing  
down to fewer articles, cited more.

In one of the few fields where this can be and has been analyzed  
thoroughly, astrophysics, which effectively has 100% Open Access (OA)  
(free online access) already, Michael Kurtz too found that with free  
online access to everything, reference lists became (a little)  
shorter, not longer, i.e., people are citing (somewhat) fewer papers,  
not more, when everything is accessible to them.
	http://adsabs.harvard.edu/abs/2005IPM....41.1395K
	http://adsabs.harvard.edu/abs/2000A%26AS..143...41K

The following seems a plausible explanation:

Before OA, researchers cited what they could afford to access, and  
that was not necessarily all the best work, so they could not be  
optimally selective for quality, importance and relevance. (Sometimes  
-- dare one say it? -- they may even have resorted to citing "blind,"  
going by just the title and abstract, which they could afford, but not  
the full text, to which they had no subscription.)

In contrast, when everything becomes accessible, researchers can be  
more selective and can cite only what is most relevant, important and  
of high quality. (It has been true all along that about 80-90% of  
citations go to the top 10-20% of articles. Now that the top 10-20%  
(along with everything else in astrophysics), is accessible to  
everyone, everyone can cite it, and cull out the less relevant or  
important 80-90%.

This is not to say that OA does not also generate some extra citations  
for lesser articles too; but the OA citation advantage is bigger, the  
better the article -- the "quality advantage" -- (and perhaps most  
articles are not that good!).  Since the majority of published  
articles are uncited (or only self-cited), there is probably a lot  
published that no amount of exposure and access can render worth citing!
	http://eprints.ecs.soton.ac.uk/11688/

(I think there may also exist some studies [independent of OA] on  
"like citing like" -- i.e., articles tending to be cited more at their  
own "quality" level rather than a higher one. [Simplistically, this  
means within their own citation bracket, rather than a higher one.] If  
true, this too could probably be analyzed from an OA standpoint. [Does  
anyone on SIGMETRICS know of such studies -- preferably controlled for  
same-journal and co-author circle-citations?])

But the trouble is that apart from astrophysics and high energy  
physics, no other field has anywhere near 100% OA: It's closer to 15%  
in other fields. So aside from a global correlation (between the  
growth of OA and the average length of the reference list), the effect  
of OA cannot be very deeply analyzed in most fields yet.

In addition, insofar as OA is concerned, much of the Evans effect  
seems to be based on "legacy OA," in which it is the older literature  
that is gradually being made accessible online or freely accessible  
online, after a long non-online, non-free interval. Fields differ in  
their speed of uptake and citation latencies. In physics, which has a  
rapid turnaround time, there is already a tendency to cite recent work  
more, and OA is making the turnaround time even faster.

In longer-latency fields, the picture may differ. For the legacy-OA  
effect especially, it is important to sort fields by their citation  
turnaround times; otherwise there can be biases (e.g. if short- or  
long-latency fields differ in the degree to which they do legacy OA  
archiving). http://eprints.ecs.soton.ac.uk/10713/

If I had to choose between the explanation of the Evans effect as a  
recency/bandwagon effect, as Evans interprets it, or as an increased  
overall quality/selectivity effect, I'd choose the latter (though I  
don't doubt there is a bandwagon effect too). And that is even without  
going on to point out that Tenopir & King, Gingras and others have  
shown that -- with or without OA -- there is still a good deal of  
usage and citation of the legacy literature (though it differs from  
field to field).

I wouldn't set much store by "skimming serendipity" (discovery of  
adjacent work while skimming through the print issue), since online  
search and retrieval has at least as much scope for serendipity.
	http://www.eprints.org/openaccess/self-faq/#21.Serendipity

Are online and free online access broadening or narrowing research?  
They are broadening it by making all of it accessible to all  
researchers, focusing it on the best rather than merely the  
accessible, and accelerating it.

Stevan Harnad
http://www.eprints.org/openaccess/