A number is a very coarse proxy here. It should include additional aspects such as APC caps, preference for green or gold, infrastructure support, licensing concerns, embargo concerns, and more.

This data should always be used with the caveat that it is likely skewed towards UK/European/Western organisations based on its (limited) funding from Jisc - for example, Japan is listed as having no policies although at least two major funders have such a policy: http://openscience.jp/oa/oa-po...