1. A method comprising: by one or more computing devices, accessing a plurality of user profiles corresponding to a plurality of users and a plurality of content objects, wherein: the users belong to a social network; and each of the users has contributed at least one of the content objects to the social network; ranking the users in descending order based on a number of content objects each of the users has contributed to the social network; representing in log space ranks of the users versus in log space numbers of content objects contributed by the users; determining a threshold rank based on an increasing rate of the ranks of the users, a decreasing rate of the numbers of content objects, and a predetermined value in the log space; and identifying from among the users, those users ranked at and above the threshold rank as high-volume content contributors for the social network.