Andrew Gray <andrew.gray(a)dunelm.org.uk> writes: I agree, though I think one reason the studies are oriented that way (besides convenience of data) is that a main policy-evaluation goal of such studies is to answer the question: is the OA / non-OA decision for a journal one that will significantly affect their impact factor? If going OA improves citations, then that's an argument in favor of going OA. To answer that question, the relevant comparison is OA vs. non-OA journals (preferably comparing similarly situated journals within fields). Papers from non-OA journals that are nonetheless available on the internet for free make more a more complex case, both in terms of how they got there, and what the policy implications should be. Though still an interesting case! -- Mark J. Nelson Anadrome Research http://www.kmjn.org

Regarding the question from the OP [oh, that's me!], here are some search terms that produce relevant results, citation frequency wikipedia -"cite wikipedia" -"citing sources" Interestingly, the first paper I found suggests that the trend is the almost the opposite of the one I was thinking would obtain. «In the present study, we show that inclusion of articles in Wikipedia does not increase the propensity of articles to be cited. Interestingly, the reverse is reported to be true, i.e., Wikipedia selectively lists high impact articles shortly after their publication.» - Marashi et al., "Impact of Wikipedia on citation trends" This work is mentioned in a previous Research Newsletter, here: https://meta.wikimedia.org/wiki/Research:Newsletter/2013/August#Briefly ... which is probably what I was remembering. A slightly expanded treatment by the same authors is available as: "Impact of inclusion of scholarly references in Wikipedia on citation trends" I don't see that the result has been replicated by other researchers. Some related themes are discussed from an (optimistic) technical engineering point of view in, here: «Our results show that a) classical query expansion using terms extracted from query pages leads to increased precision, and b) link distance between query and book pages in Wikipedia provides a good indicator of relevance that can boost the retrieval score of relevant books in the result ranking of a book search engine.» - Koolen et al., "Wikipedia pages as entry points for book search" -Joe On Thu, Aug 20 2015, Daniel Mietchen wrote:

They did; DOAJ seems to have been the method used to determine whether a journal was OA or not (which is fair enough). Andrew. On 21 August 2015 at 12:50, Federico Leva (Nemo) <nemowiki(a)gmail.com> wrote: -- - Andrew Gray andrew.gray(a)dunelm.org.uk