Organizing search results

A Non-Transitory computer-readable medium tangibly storing instructions executable on one or more computers, the instructions including instructions for:

• retrieving at least one listing based on a search query, the query including at least one parameter associated with an element of a hierarchical index;
• determining a normalized click-through rate for each of the at least one listings,
• the normalized click-through rate for a listing being based on a click-through rate for the listing that is adjusted according to one or more positions in which the listing has been displayed in each of a plurality of sets of search results;
• and
• determining a position for the at least one listing in a set of search results based at least in part on an aggregation of the normalized click-through rates associated with at least one level of a hierarchical index;
• aggregating normalized click-through rates associated with a first level of a hierarchical index into an aggregate normalized click-through rate for the first level;
• aggregating normalized click-through rates associated with a second level of a hierarchical index into an aggregate normalized click-through rate for the second level;
• determining a deviation of the difference between the second-level normalized click-through rates and the first-level normalized click-through rates;
• comparing the deviation with a predetermined threshold;
• and
• accepting the first-level normalized click-through rate as a valid aggregation when the deviation is below the predetermined threshold.