11. A method implemented by a data processing apparatus, comprising: accessing an index of first and second resources, the first resources being resources that are different from the second resources; for each indexed first resource: selecting, from a query log, queries for which search results referencing the first resource were selected at a user device in response to the queries; for each of the queries, accessing data specifying an actual search property ratio for the query, the actual search property ratio being a ratio of a first number of times the query was used to search first resources and a second number of times the query was used to search second resources; and determining, by the data processing apparatus, a resource search property ratio score for the first resource based on the actual search property ratios of each of the queries; identifying websites hosting the first resources, each website hosting one or more of the first resources; and determining, for each of the websites, a website search property ratio based on the actual search property ratios of each of the queries for which search results referencing the first resource hosted on the website were selected; receiving a query for a search of the first resources; selecting at least a proper subset of resources that are determined to be responsive to the query; determining an actual search property ratio of the query that is proportional to a number of times the query was submitted for a search of the second resources to a number of times that the search query was submitted for a search of the first resources; and determining an insertion score based on a first insertion score that is proportional to the actual search property ratio and a first weighting value and a second insertion score from a proper subset of resources that have the highest first search scores for the query and based on the resource search property ratio scores of the proper subset of resources and a second weighting value.
11. A method implemented by a data processing apparatus, comprising: accessing an index of first and second resources, the first resources being resources that are different from the second resources; for each indexed first resource: selecting, from a query log, queries for which search results referencing the first resource were selected at a user device in response to the queries; for each of the queries, accessing data specifying an actual search property ratio for the query, the actual search property ratio being a ratio of a first number of times the query was used to search first resources and a second number of times the query was used to search second resources; and determining, by the data processing apparatus, a resource search property ratio score for the first resource based on the actual search property ratios of each of the queries; identifying websites hosting the first resources, each website hosting one or more of the first resources; and determining, for each of the websites, a website search property ratio based on the actual search property ratios of each of the queries for which search results referencing the first resource hosted on the website were selected; receiving a query for a search of the first resources; selecting at least a proper subset of resources that are determined to be responsive to the query; determining an actual search property ratio of the query that is proportional to a number of times the query was submitted for a search of the second resources to a number of times that the search query was submitted for a search of the first resources; and determining an insertion score based on a first insertion score that is proportional to the actual search property ratio and a first weighting value and a second insertion score from a proper subset of resources that have the highest first search scores for the query and based on the resource search property ratio scores of the proper subset of resources and a second weighting value. 12. The method of claim 11 , wherein the first weighting value is proportional to a frequency of occurrence of the query, and the second weighting value is proportional to a number of times the search results referencing resources in the proper subset of resources query have been selected.