The compatibility score of members of a social network is based on the compatibility of their expressed interests. The compatibility score between any two interests is calculated as the log of the estimated probability that a member of the social network will express both interests divided by the product of: (i) the estimated probability that a member of the social network will express the first of the two interests and (ii) the estimated probability that a member of the social network will express the second of the two interests. The compatibility score between two individuals is calculated as the sum of the compatibility scores between each interest appearing in a set of interests expressed by the first of the two individuals and each interest appearing in a set of interests expressed by the second of the two individuals.