The influence of OA [open access] is more modest than many have proposed, at ~8% for recently published research, but our work provides clear support for its ability to widen the global circle of those who can participate in science and benefit from it.On one hand, Philip Davis from Cornell University argued that "Open Access: Increased Citations Not Guaranteed" in the title of his letter. On the other hand, Michael Eisen (HHMI and UC Berkeley) and Steven Salzberg (University of Maryland) stated that "Open Access: The Sooner the Better" -- In their opinion, "the 8% statistic that Evans and Reimer highlight is misleading. .... In particular, when articles were made freely available within 2 years of publication, their citations increased by almost 20%." Interesting, the same issue also published Evens' response, addressing comments and criticisms from other scientists.
Another very interesting point: Eisen and Salzberg also expressed their concern about the unavailability of the raw citation information used in the Evans and Reimer report, saying this "is an astonishing violation of the norms of science, and the explicitly stated publication policies of Science." In response to this point, Science's Editor noted that "[Science] do not preclude our authors from obtaining data from commercial sources when those are the only sources of the data and when those data are available to the scientific community."
Overall, the discrepancies about the influence of open access on citations, and how to possibly resolve them in relation to the availability of the original data, are typical in science. Presumably, this is a relatively simple case. Yet, there are still many variables in data selections and interpretations etc. Even if the "raw data" are made available, which certainly would be a big help, I still doubt that the discrepancies could be resolved. On the other hand, the "raw data" are only secondary in the sense that they were collected by Evans and Reimer using some specific criteria. If the detailed steps are made available such that the reported figures and tables can be reproduced by those who have access to the commercial sources, then things would become clear. In other words, it is not just the data nor the numbers (in published figures and tables), but the exact procedures, of how the numbers have been produced from the original data, that could provide a convincing resolution (if there is one).