1. A method comprising: maintaining, by one or more computing devices, one or more data stores storing a social graph comprising a plurality of nodes and a plurality of edges, the nodes comprising user nodes corresponding to users of a social-networking system and concept nodes corresponding to concepts, wherein each edge connects two of the nodes, each of the edges being associated with an affinity score; determining, by one or more computing devices, a confidence score between a first one of the user nodes and a first one of the concept nodes based at least in part on one or more affinity scores associated with one or more edges between the first one of the user nodes and the first one of the concept nodes in the social graph; and storing, by one or more computing devices, the confidence score in the data stores.