19. A system comprising: a memory; and a processor coupled to the memory, to: provide a candidate category hierarchy, including candidate categories, and a mapping between reference pages and the candidate categories, including mapped reference pages; obtain population usage data of each of the mapped reference pages; use the population usage data to determine a population traffic metric for each of the candidate categories; generate a population categories by using the population traffic metric of each of the candidate categories; produce a population category hierarchy including the population categories; and modify the mapping to create a population mapping, wherein the mapped reference pages are re-mapped to the population categories to create the population mapping.
19. A system comprising: a memory; and a processor coupled to the memory, to: provide a candidate category hierarchy, including candidate categories, and a mapping between reference pages and the candidate categories, including mapped reference pages; obtain population usage data of each of the mapped reference pages; use the population usage data to determine a population traffic metric for each of the candidate categories; generate a population categories by using the population traffic metric of each of the candidate categories; produce a population category hierarchy including the population categories; and modify the mapping to create a population mapping, wherein the mapped reference pages are re-mapped to the population categories to create the population mapping. 20. The system of claim 19 , wherein the processor is to generate the population categories from the candidate categories by using the population traffic metric includes instructions by: deleting a candidate category from inclusion in the population categories when the population traffic metric of the candidate category falls below an inclusion threshold; and retaining a different candidate category as a population category when the population traffic metric of the different candidate category exceeds the inclusion threshold.