1. A computer-implemented 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; 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 associated with each keyword appearing in a listing from the identified listings, each relevance score representing a desirability measure for a keyword with which the relevance score is associated, the desirability measure determined based on a calculated difference between a measure of demand and supply for a respective keyword in the listing; and displaying the organized listings.