Systems and methods are disclosed for systems and user interfaces for rapid analysis of viewership information. One of the methods includes accessing databases storing viewership information associated with segments, with each segment being associated with common features of viewers. Measures of association between the segment and content items are maintained for each segment. An interactive user interface is presented via a user device, the interactive user interface enabling creation of a customized viewing audience. The interactive user interface receives user input indicating a segment, identifies similar segments based on associations between features of the segment and of other segments, and presents the identified segments. Analysis information associated with the segments is presented for at least one of the one or more segments, with the segments being included in the customized viewing audience.