1. A computer-implemented method comprising: determining, by a computer, a plurality of demographic groups of users of a social networking system, the determining comprising, for each demographic group of users, selecting the users based on demographic characteristics of the users; for each demographic group of users: selecting a set of features for use for the demographic group based on the demographic characteristics of the users of the demographic group; training a model configured to rank news feed stories for presentation to users of the demographic group, the training utilizing training sets obtained from the demographic group of users, the model comprising the set of features associated with the demographic group; identifying stories for presentation to a user belonging to a demographic group; and ranking the stories identified for presentation to the user using the model corresponding to the demographic group of the user and presenting the stories to the user based on the ranking.