This last calculation comes as a surprise to me that there would be no overlap between Green and Gold or Green and Delayed access articles. My own work and that of my colleagues is a prime example. We regularly maintain electronic copies of our peer-reviewed published works on our professional author and institutional pages, and are required by some funders to submit to them copies for their electronic repositories. Sometimes these copies are usable, pre-publication (Green) versions, and at other times they are Gold or Delayed versions. Are we alone in this practice?
(2) The Finnish study focuses its attention on peer-reviewed articles. Is this the right approach? Reasonably one may argue that exclusively focusing on peer-reviewed articles is the best measure of open access advances because they are likely to be more sought after by, and therefore, more valuable to the research community. As such, demand drives cost and value up, diminishing incentives for publishers of peer-reviewed journals to go to open access. Others may argue it is more a pragmatic matter of scholarly integrity.
In significant contrast, the U.S. legal community largely lacks a peer-review component, and in comparison to many other disciplines, probably makes greater use on a daily basis of published materials generally, and non-peer-reviewed materials specifically, than any other discipline. Historically, these non-peer-reviewed materials have fetched a handsome profit for publishers.
The legal community relies heavily, and almost exclusively, on published court opinions (i.e., decisions) and to a lesser extent on law review articles. The American Bar Association (2007) reported there were 1,143,358 practising attorneys in the United States in 2007. Judges often rely on law clerks to draft portions of a decision. While many judges consult one another before issuing a decision, they have no obligation to do so, and publishers of these decisions play no role in editing them -- the decision, in this respect, is sacrosanct (except under the scrutiny of a higher court).
Law review articles in the United States rarely undergo peer review. All but a relative handful of law journals are edited by law students, who are selected for the editorial boards of a given journal published by the student's law school. The vast majority of law review article authors are law faculty members.
All this has been to say, or to question, whether the sole focus on peer-reviewed articles to measure advances in open access is the best approach for doing so. It may be. However, the legal community may not be equally benefiting from open access of this nature. Free repositories of court decisions are becoming more widespread. Yet, comprehensive databases of court decisions and law review articles remain controlled by legal publishers.
American Bar Association, Statistical Resources: National Lawyer Population by State (2007), available at http://www.abanet.org/marketresearch/2008_NATL_LAWYER_by_State.pdf
Björk, B-C, Roos, A. & Lauri, M. (2009). "Scientific journal publishing: yearly volume and open access availability" Information Research, 14(1) paper 391. [Available from 12 January, 2009 at http://informationr.net/ir/14-1/paper391.html]
Thomson Scientific: http://isiwebofknowledge.com/
Ulrich's Periodicals Directory: http://www.ulrichsweb.com/ulrichsweb/
U.S. Courts, 2007 Judicial Facts and Figures (2007), available at http://www.uscourts.gov/judicialfactsfigures/2007/all2007judicialfactsfigures.pdf