16. The non-transitory computer-readable medium of claim 15 , wherein comparing the pre-computed response to the first query and the responses to the one or more other sub-queries comprises identifying an intersection of the number of web page impressions satisfying the first query and a number of web page impressions satisfying each of the one or more other sub-queries.
15. The non-transitory computer-readable medium of claim 13 , further comprising storing a number of web page impressions satisfying the first query.