2. A method in a computing device for calculating a bid amount for a keyword, the method comprising: collecting, at one or more computer systems, conversion information for the keyword indicating financial benefit resulting from users selecting advertisements displayed with content that relates to the keyword, the financial benefit being organized into categories; determining, at the one or more computer systems, a category-specific advertising expense factor for each category; calculating, at the one or more computer systems, a category-specific product for each category, the category specific product calculated by multiplying the financial benefit for the category by the category-specific advertising expense factor determined for the category; generating, at the one or more computer systems, a summation of the calculated category-specific products; generating, at the one or more computer systems, a quotient, wherein the quotient is the summation of the category-specific products divided by a number of sessions with financial benefit; and generating, at the one or more computer systems, a bid amount for the keyword based at least in part on the quotient multiplied by a forecast conversion rate, the forecast conversion rate comprising a predicted percentage of clickthroughs associated with the keyword that results in a conversion.
2. A method in a computing device for calculating a bid amount for a keyword, the method comprising: collecting, at one or more computer systems, conversion information for the keyword indicating financial benefit resulting from users selecting advertisements displayed with content that relates to the keyword, the financial benefit being organized into categories; determining, at the one or more computer systems, a category-specific advertising expense factor for each category; calculating, at the one or more computer systems, a category-specific product for each category, the category specific product calculated by multiplying the financial benefit for the category by the category-specific advertising expense factor determined for the category; generating, at the one or more computer systems, a summation of the calculated category-specific products; generating, at the one or more computer systems, a quotient, wherein the quotient is the summation of the category-specific products divided by a number of sessions with financial benefit; and generating, at the one or more computer systems, a bid amount for the keyword based at least in part on the quotient multiplied by a forecast conversion rate, the forecast conversion rate comprising a predicted percentage of clickthroughs associated with the keyword that results in a conversion. 5. The method of claim 2 wherein the financial benefit is generated from purchases of items within a category during a session initiated with the selection of an advertisement for the keyword and the determining of the bid amount includes accumulating combinations for each category of the financial benefit for that category and the category-specific advertising expense factor for that category and normalizing the accumulated combinations by number of sessions resulting in the financial benefit.