1. A computer-implemented method, comprising: (a) receiving a first set of elements, each element in the first set being assigned to one of a plurality of categories and having one of a plurality of content profiles associated therewith; (b) receiving a second set of elements, each element in the second set having one of the content profiles associated therewith; and (c) using a processor to calculate, based on the content profiles associated with and the categories assigned to elements in the first set and the content profiles associated with the elements of the second set and without assigning the elements of the second set to the categories individually, a distribution of elements of the second set over the categories, which distribution is not constrained to be the same as a distribution of elements of the first set over the categories.