1. A method comprising: using at least one processor coupled to a memory, selecting a random sample of member profiles in an on-line social network system, a member profile from the member profiles representing a member of the on-line social network system, the on-line social network system maintaining one or more member categories, the random sample of member profiles comprising a plurality of phrases, each member profile from the member profiles comprising two or more phrases; for each phrase from the plurality phrases, obtaining a weight value, a weight value of a phrase from the plurality phrases calculated based on phrases present in the random sample of member profiles and a target category from the one or more member categories, a combination of a phrase from the plurality phrases and its weight value comprising a weighted phrase, the plurality of phrases with their respective weight values comprising a plurality of weighted phrases; storing the plurality of weighted phrases in a database; accessing a member profile from the member profiles and the plurality of weighted phrases; based on a presence of one or more phrases from the plurality of weighted phrases in the member profile, generating a category score for the member profile, the category score indicating a likelihood of the member profile being associated with the target category; comparing the category score of the member profile to a threshold value; and based on a result of the comparing, selectively identifying the member profile as associated with the target category.