A study to be presented in Toronto this June at the International Conference on Electronic Publishing measures the prevalence of open-access publishing. The study’s authors estimated that 4.6 percent of all papers published in 2006 were accessible in primary open-access journals, and an additional 3.5 percent were available after embargo. If they included free copies sitting in repositories or accessible from people's homepages, the total number of free papers came to 19.4 percent.