Evans, James A. (2008) Electronic Publication and the Narrowing of Science and Scholarship Science 321(5887): 395-399 DOI:10.1126/science.1150473
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 free online.
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!
(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.)
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 (slightly negative) 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 their 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).
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” (the discovery of adjacent work while skimming through print issues), since online search and retrieval has at least as much scope for serendipity. (And one would expect more likelihood of a bandwagon effect without OA, where authors may tend to cite already cited but inaccessible references “cite unseen.”)
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.