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 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.
7. The method of claim 1 , wherein the demographic characteristics for determining a demographic group include one or more of: age of users, ethnicity of users, gender of users, and income of users.