Ask one census frame (top1k, top10k, top100k) a question across every site it measured, with the census field ids (fields=1 lists them): where= (all hold), not= (none hold), any= (at least one), rank_max=. Returns the matching sites in rank order, the count, the denominator (sites where every named field could be measured) and its 95% interval, from one named run, signed. The first 100 matches are free; a licence key pages up to 2,000 at a time and adds format=csv.