17. The computer-executed method of claim 1 , comprising: filtering the first population based on a filtering criteria; and wherein the affinity score is determined based on an intersection of social media users in the filtered first population and the second population.
19. The computer-executed method of claim 17 , wherein the filtering criteria is a content criteria, and wherein filtering the first population based on demographic criteria comprises: for each social media user in the first population, extracting social media features from a plurality of social media content items authored by the social media user; comparing the extracted features to the content criteria; and removing the social media user from the first population responsive to determining that none of the extracted features match the content criteria.