Abstract: Methods, systems, and apparatus, including computer programs encoded on a computer storage medium, for identifying a set of items that are displayed to a user of a social networking service, the items comprising digital content distributed using the social networking service and being associated with item features, the item features comprising item-dependent features and user-dependent features; receiving feature values that are associated with one of an item-dependent feature and a user-dependent feature; receiving probabilities that are associated with a group and reflecting a likelihood that the user is a type of user associated with the group, the groups including a set of weights; determining an item score based on the feature values and a set of weights to provide item scores, the set of weights being identified based on the probabilities; and determining a subset of items to be displayed to the user based on the item scores.