How much science is there? How open is it?
The extent to which open access has been adopted by researchers varies amongst the disciplines. Science is probably the most open. Xkcd comics depicted open-access publishing in science for a special (open access) issue of Science in 2013. Click the drawing to see the full graphic.
Archambault, E, Amyot, D, Deschamps, P, Nicol, A, Rebout, L, and Roberge, G (2013). Proportion of open access peer-reviewed papers at the European and world levels—2004-2011. Brussels: Science-metrix; European Commission. Available at http://www.science-metrix.com/pdf/SM_EC_OA_Availability_2004-2011.pdf
