1. A method performed by one or more server devices, the method comprising: receiving, by at least one of the one or more server devices, a search query from a client device; identifying, by at least one of the one or more server devices, documents as search results relevant to the search query, where each of the search results has a respective first score; ranking, by at least one of the one or more server devices, the search results, based on the respective first scores, to form a ranked list of search results, where each of the search results has a respective position, within the ranked list, that is based on the ranking; determining, by at least one of the one or more server devices, a selection rate corresponding to each of the positions in the ranked list, a particular selection rate, corresponding to a particular position, being determined based on selections from the particular position, and determining the selection rate for one of the positions in the ranked list including: selectively: obtaining information regarding an actual selection rate, corresponding to the one of the positions, from observed selections, or estimating a selection rate corresponding to the one of the positions, and using the actual selection rate or the estimated selection rate as the selection rate for the one of the positions; identifying, by at least one of the one or more server devices, categories with which the search results are associated; generating, by at least one of the one or more server devices, second scores for the categories based on the selection rates, where the second score, for a particular one of the categories, is based on the selection rate corresponding to the position, in the ranked list, of one or more of the search results that are associated with the particular one of the categories, generating the second scores for the categories including: generating the second score, for one of the categories, based on a combination of a plurality of selection rates corresponding to positions, in the ranked list, of a set of the search results that are associated with the one of the categories; selecting, by at least one of the one or more server devices, a plurality of the categories based on the second scores of the categories; selecting, by at least one of the one or more server devices, a plurality of the search results for the selected plurality of categories; generating, by at least one of the one or more server devices, a search result document that includes information regarding the selected plurality of categories and information regarding the selected plurality of search results; and providing, by at least one of the one or more server devices, the search result document for display on the client device.
1. A method performed by one or more server devices, the method comprising: receiving, by at least one of the one or more server devices, a search query from a client device; identifying, by at least one of the one or more server devices, documents as search results relevant to the search query, where each of the search results has a respective first score; ranking, by at least one of the one or more server devices, the search results, based on the respective first scores, to form a ranked list of search results, where each of the search results has a respective position, within the ranked list, that is based on the ranking; determining, by at least one of the one or more server devices, a selection rate corresponding to each of the positions in the ranked list, a particular selection rate, corresponding to a particular position, being determined based on selections from the particular position, and determining the selection rate for one of the positions in the ranked list including: selectively: obtaining information regarding an actual selection rate, corresponding to the one of the positions, from observed selections, or estimating a selection rate corresponding to the one of the positions, and using the actual selection rate or the estimated selection rate as the selection rate for the one of the positions; identifying, by at least one of the one or more server devices, categories with which the search results are associated; generating, by at least one of the one or more server devices, second scores for the categories based on the selection rates, where the second score, for a particular one of the categories, is based on the selection rate corresponding to the position, in the ranked list, of one or more of the search results that are associated with the particular one of the categories, generating the second scores for the categories including: generating the second score, for one of the categories, based on a combination of a plurality of selection rates corresponding to positions, in the ranked list, of a set of the search results that are associated with the one of the categories; selecting, by at least one of the one or more server devices, a plurality of the categories based on the second scores of the categories; selecting, by at least one of the one or more server devices, a plurality of the search results for the selected plurality of categories; generating, by at least one of the one or more server devices, a search result document that includes information regarding the selected plurality of categories and information regarding the selected plurality of search results; and providing, by at least one of the one or more server devices, the search result document for display on the client device. 5. The method of claim 1 , further comprising: comparing the respective first scores to a threshold value; and removing one of the search results, that has a respective first score that is less than the threshold value, before generating the second scores for the categories, where the second scores are generated without using information regarding the removed one of the search results.