Abstract: Methods, systems, and apparatus, including computer programs encoded on a computer storage medium, for determining a resource's reachability score. In one aspect, a method includes identifying one or more secondary resources reachable through one or more links of a primary resource wherein the secondary resources are within a number of hops from the primary resource; determining an aggregate score for the primary resource based on respective scores of the secondary resources wherein each one of the respective scores is calculated based on prior user interactions with a respective secondary resource; and providing the aggregate score as an input signal to a resource ranking process for the primary resource when the primary resource is represented as a search result responsive to a query.