18. The non-transitory computer-readable storage medium of claim 17 , wherein a first model corresponding to a first demographic group of users is trained using a first set of features and a second model based on a second demographic group of users is trained using a second set of features.
17. A non-transitory computer-readable storage medium storing computer-executable code for ranking news feed stories of a social networking system, the code comprising instructions for: 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 as plurality of users based on demographic characteristics of the users; for each demographic group of users, generating a model configured to rank news feed stories for presentation to users from the demographic group, the model configured to receive as input, one or more user attributes describing a viewing user and ranking newsfeed stories for the viewing user based on the one or more user attributes, the generating of the model comprising; selecting a set of features for the demographic group based on the characteristics of the users of the demographic group; training the model, the training utilizing training sets obtained from the demographic group of users, the model comprising the selected set of features; identifying stories for presentation to a user belonging to a demographic group; providing one or more attributes describing the user as input to the model; and ranking the stories identified for presentation to the user using the model and sending the stories for presentation to the user based on the ranking.