Early indications are that the NIH shift to a mandatory public access policy - which took effect this April - is having quite an impact!
The estimated compliance rate from April to August 2008 is 56% (30% author manuscripts, 26% publisher PDFs), up from 19% for 2005-2007 (12% author manuscripts, 7% publisher PDFs).
44% of NIH-funded research results covered under the policy for April to August 2008 is still missing; however, with a maximum one-year embargo permitted, it is likely too early to draw any conclusions. Assuming a good percentage of the researchers will want further funding, I would anticipate an increase in the percentage of works publicly available both in the April-August 2008 time frame, and even more in the future, as researchers, libraries, and universities become more familiar with the details of the policy, and how to comply.
From: U.S. National Institutes of Health. Analysis of Comments and Implementation of the NIH Public Access Policy. Undated.
Thanks to Peter Suber on Open Access News.
This post is part of the Dramatic Growth of Open Access Series.