1. A method for developing a population category hierarchy, comprising: providing a candidate category hierarchy, including a number of candidate categories, and a mapping between a number of reference pages and the number of candidate categories, including a number of mapped reference pages; obtaining population usage data of each of the number of mapped reference pages; using the population usage data to determine a population traffic metric for each of the number of candidate categories; generating a number of population categories by using the population traffic metric of each of the number of candidate categories; and producing a population category hierarchy including the number of population categories.