When people refer to open access journals, there are actually a number of different models that they have in mind. Nick Fowler, head of strategy at Elsevier, breaks them down into the four main flavors.
Author pays BioMed Central and PLoS both utilize this approach, which relies on authors paying a fee to be published and then not having subscription charges for anyone to access the journal. Fowler says that about 1 percent of all articles are published in author-pays journals, and that that number has remained consistent for the past five years or so.
This is a hybrid model, based primarily on subscription fees, in which authors are asked after publication whether they're interested in paying a fee to sponsor the article, thereby making it freely available to the community. According to Fowler, only about one in 1,000 authors generally pays the fee to sponsor an article. But more institutions are beginning to take advantage of this concept. Wellcome Trust and Howard Hughes Medical Institute, for instance, both have negotiated deals with Elsevier in which they pay the fee to sponsor articles authored by their researchers.
This is the model used by Elsevier's Cell, among other journals. Publishers using the delayed access approach keep literature behind closed doors for a certain period of time — often 12 months — and then make it freely available through a website. In life sciences, Fowler says, research moves so rapidly that releasing papers after a year doesn't carry the threat of cancelled subscriptions, so more publishers are willing to try this.
Also known as public access, this approach means that papers are deposited in some kind of central repository such as PubMed. Often the manuscript being archived doesn't exactly match what appears in the journal; it have errors or omissions, Fowler says. This model is being used more and more as funding agencies introduce policies requiring that the research they're making possible is made freely available within six months or a year.