14. A non-transitory computer-readable storage medium comprising: instructions for identifying a topic group of users of a social networking system that have expressed an affinity for a page of the social networking system that corresponds to a first topic; instructions for identifying a category that includes the first topic and a plurality of other topics; instructions for identifying a category group of users of the social networking system that have expressed an affinity for a page corresponding to at least one of the topics included in the category; instructions for identifying a plurality of candidate pages of the social networking system, each candidate page having a corresponding candidate topic; instructions for, for each candidate page of the plurality of pages of a social networking system computing a user interest measure quantifying an amount of interest expressed by users of the topic group in the topic corresponding to the candidate page, computing a category interest measure quantifying an amount of interest expressed by users of the category group in the topic corresponding to the candidate page, and computing a divergence measure based on the user interest measure and the category interest measure; instructions for generating, for the first topic, a topic profile based on the divergence measures; and instructions for storing the topic profile.
14. A non-transitory computer-readable storage medium comprising: instructions for identifying a topic group of users of a social networking system that have expressed an affinity for a page of the social networking system that corresponds to a first topic; instructions for identifying a category that includes the first topic and a plurality of other topics; instructions for identifying a category group of users of the social networking system that have expressed an affinity for a page corresponding to at least one of the topics included in the category; instructions for identifying a plurality of candidate pages of the social networking system, each candidate page having a corresponding candidate topic; instructions for, for each candidate page of the plurality of pages of a social networking system computing a user interest measure quantifying an amount of interest expressed by users of the topic group in the topic corresponding to the candidate page, computing a category interest measure quantifying an amount of interest expressed by users of the category group in the topic corresponding to the candidate page, and computing a divergence measure based on the user interest measure and the category interest measure; instructions for generating, for the first topic, a topic profile based on the divergence measures; and instructions for storing the topic profile. 15. The non-transitory computer-readable storage medium of claim 14 , further comprising: instructions for computing a first topic affinity score for a first user not in the topic group by applying the topic profile to information of the social networking system about the first user; and instructions for predicting, based on the first topic affinity score, that the first user has an affinity for the first topic.