Abstract: The present disclosure includes systems and techniques relating to ranking search results of a search query. In general, the subject matter described in this specification can be embodied in a computer-implemented method that includes: receiving multiple features, including a first feature indicative of presentation bias that affects document result selection for search results presented in a user interface of a document search service; obtaining, based on the multiple features, information regarding document result selections for searches performed using the document search service; generating a prior model using the information, the prior model representing a background probability of document result selection given values of the multiple features; and outputting the prior model to a ranking engine for ranking of search results to reduce influence of the presentation bias.