Open Access is growing. According to a recent report 50% of 2011 papers are free! | Open Science

"According to 'Proportion of Open Access peer-reviewed Papers at the European and World Levels-2004-2011', we can observe an increasing number of scientific articles published in Open Access. For example, almost half of the articles from 2011 are now available for free. Looking at open access practices in a wider timeframe, it can be observed that 43% of the articles published from 2008 to 2011 are OA. This increase, admittedly not particularly fast, is well illustrated by the graph below ... The authors recognize that the growth rate is not high and add that the growing number of OA papers is partially influenced by the fact that researchers make their older works freely available. This, however, does not necessarily apply to new articles. As we read: 'Finally, when one looks at the availability curve, it can be seen that the availability falls somewhat for the most recent few years. This is likely due to the presence of embargo for some of the subscription based journals which make all articles freely available to all after a few years—a practice which may be called 'delayed OA'.

The report communicates a clear message: the number of OA articles has successively increased over the last few years. This growth has been determined by a variety of factors, ranging from a greater awareness of OA among scientists, efficient PR of this publishing model to mandatory policies. Nevertheless, the report acutely shows that there is still much to be done to disseminate Open Access."