1. A method performed by data processing apparatus, the method comprising: receiving data specifying a search query, and a location of a user device from which the search query was received; receiving data specifying a set of documents determined to be relevant to the search query, the data specifying, for each of the documents, a respective search score indicative of the relevance of the document to the query and a ranking of the documents according to a first order based on the search scores, and wherein a proper subset of the documents are local documents, wherein each of the local documents is a document that is specified as having local significance to a geographic location of a user device; determining that a first local document in the proper subset of the local documents is eligible for a demotion operation that adjusts the first local document's respective search score to demote the rank of the first local document in the first order, the determination based at least in part on a proximity measure based on the geographic location of the user device and a geographic location specified for the first local document, and in response to the determination: for each second local document in the proper subset of local documents, determining a proximity measure that is based on the geographic location of the user device and the geographic location specified for the second local document; and adjusting the search score of the first local document to demote the first local document's ranking the first order when at least one of the proximity measures indicates a respective second local document has a specified geographic location that is within a threshold distance of the geographic location of the user device.