“Open access” only really gets interesting when users and product developers have access to a critical mass of content. I’ll leave the definition of “Critical mass” vague at this point, but it probably means something like 80-90% of the most cited content in a field such as biomedical research. But for this to happen the funding agencies across the discipline need to take hold of the reigns and shape the conversion process.

PMCOA

Last year a number of key European funding sources did give their full backing for open access publishing. The UK government announced that it would require much of the country’s taxpayer-funded research to publicly available from April 2013 onwards and the European Commission said that it would require all work funded by its Horizon 2020 research program to be freely available. Can we now begin to imagine an STM publishing environment in which open access is the dominant business model?

As is often the case, the future is a little easier to see in the US where since 2008 the NIH’s Public Access Policy has required scientists to submit final peer-reviewed manuscripts derived from work supported by NIH funds to the digital archive PubMed Central. Initially compliance was an issue, but from Spring 2013 NIH will delay processing of non-competing continuation awards if publications arising from grant awards are not in compliance with the Public Access Policy.

So how much free full text access is there? The graphic above compares the number of articles available as free full text as a proportion of the total volume of full text content available over time on PubMed. Simple key words such as “epilepsy” and “muscular dystrophy” were used to select a particular corpus and the total numbers of articles computed using the “Free full text[sb]” and “Full text[sb]” limiters.

The fraction of available content that is free varies quite significantly across the five fields being highest for “genomics” and the orphan disease, “leishmaniasis”. It is lowest for “epilepsy”. All of the trajectories increase gradually over time reaching levels of 30-50% by 2011. The rapid fall off after that is caused by the embargo periods of 6-12 months imposed by many publishers contributing OA content.

Why the differences between the fields? This question needs more research, but from visual inspection of the PubMed result lists it would seem that new areas such as genomics are driven more by younger journals that have fully embraced the open access model, whereas fields such as epilepsy are still dominated by society and larger commercial publishers that haven’t.

If that turns out to be the case, then the future dynamics of conversion to open access (at least in biomedicine) will be determined by the interaction between the leading funding agencies and top publishers.

This will have two interesting consequences. Firstly, as the funding agencies’ OA mandates become actively enforced authors will turn increasingly to OA publishers in order to meet these requirements with a minimum of hassle, and journals such as PLoS One and repositories like Europe PubMed Central will flourish. Secondly, open access “contagion” will spill over more rapidly into other disciplines such as engineering and chemistry. After all, the Horizon 2020 program is not just about biomedicine!

So, have we reached the tipping point? This analysis suggests that the 80-90% target cannot be reached by incremental growth. Something more has to give.