13. A non-transitory computer-readable medium having instructions stored thereon, which, when executed by a computer, cause the computer to perform a method, comprising: processing a search query specifying one or more keywords to identify listings satisfying the search query, each listing from the identified listings describing an item or service offered for sale and including a title and a price; organizing the identified listings based on a composite relevance score assigned to each listing from the identified listings, the composite relevance score derived as a sum of relevance scores respectively associated with each keyword from the one or more keywords appearing in a listing from the identified listings, each relevance score representing a customer desirability measure for a keyword in the listing, the customer desirability measure determined based on a calculated difference between a measure of customer demand and supply for the keyword, the measure of customer demand for the keyword is expressed as the percentage of listings that i) are selected by a user over a period of time, and ii) have titles including words that match keywords specified in the query, and the measure of supply for the keyword is expressed as the percentage of listings satisfying the search query that include the keyword; and displaying the organized listings.
14. The computer-readable medium of claim 13 , wherein organizing the identified listings includes sorting the identified listings in descending order of the composite relevance score assigned to each listing.