28% of PubMed articles are feely available
According the Nature blog:
“the proportion of research papers freely available is slowly and steadily creeping upwards.
The chart shows the proportion of papers indexed on the (largely biomedical) PubMed repository each year that are now freely accessible: in 2009, it’s above 28%. (Some of this literature is not immediately available at the time that it is published, because of journal policies that impose embargo periods on when material can become free). (…)
Would we expect that to continue at the same rate with around 50% of the literature published in 2021 freely available?”
Van Noorden, Richard. How many research papers are freely available?. Nature News blog, Posted on 1st of August 2011.