 The difficulty of inferring injustice from socially caused disadvantage is clear in contexts where greater social provision secures incremental advantage. In such contexts, the question of how much is just will not always have an obvious answer. For example, it would at least marginally benefit wheelchair-users to have additional restricted parking spaces, but we could hardly infer an injustice from the fact that an institution provided N rather than N + 1 such spaces. Intuitively, the allotment should be proportionate to the number of wheelchair users in the community or at the facility, but that number may be uncertain, and a range of spaces would likely satisfy any proportionality  requirement.[1]  In deciding how many spaces are enough, we would receive no guidance from the indisputable fact that any disadvantage or advantage in this context would have social causes.