8. A computer-implemented method for optimizing the relative positions of sponsored and organic search results on a search results page displayed to a user, the method comprising: obtaining bidding data related to a search query by a search engine having a processor and a memory, the data including a number of bidders for the search query, their price-per-click (PPC) bid amounts, and a daily maximum spending amount for each bidder; estimating, by the search engine, a projected click-through-rate (CTR) for each possible sponsored search result position to be filled in response to the search query during a next time period based on the bidding data; estimating, by the search engine, a number of sponsored search result positions required during the next time period in order to meet the daily maximum spending amount of each bidder, based on the number of bidders and the average CTR for each position; estimating a commercial score, by the search engine, based on analysis of one or more organic search results returned in response to the search query that are associated with bidders that also bid on search terms related to the search query; and determining, by the search engine, a layout of at least two result columns to both of which to deliver the sponsored search results on the one or more search results pages based on the estimated number of positions and the commercial score.
8. A computer-implemented method for optimizing the relative positions of sponsored and organic search results on a search results page displayed to a user, the method comprising: obtaining bidding data related to a search query by a search engine having a processor and a memory, the data including a number of bidders for the search query, their price-per-click (PPC) bid amounts, and a daily maximum spending amount for each bidder; estimating, by the search engine, a projected click-through-rate (CTR) for each possible sponsored search result position to be filled in response to the search query during a next time period based on the bidding data; estimating, by the search engine, a number of sponsored search result positions required during the next time period in order to meet the daily maximum spending amount of each bidder, based on the number of bidders and the average CTR for each position; estimating a commercial score, by the search engine, based on analysis of one or more organic search results returned in response to the search query that are associated with bidders that also bid on search terms related to the search query; and determining, by the search engine, a layout of at least two result columns to both of which to deliver the sponsored search results on the one or more search results pages based on the estimated number of positions and the commercial score. 12. The method of claim 8 , where the layout comprises two left-hand columns of sponsored search results in response to the number of required positions comprises more than twelve and the commercial score comprises at least 50%.