Systems, methods, and devices relating to determining viewership data are described herein. In a method, viewing data associated with a household is received. A first portion of the viewing data is indicative of video programming associated with a first video device and a second portion of the viewing data is indicative of video programming associated with a second video device. One or more characteristics associated with the first and second portions of the viewing data are determined. Based on the one or more characteristics and a comparison of the respective video programming associated with the first and second video devices, it is determined that the first portion of the viewing data is duplicative, at least in part, with the second portion of the viewing data.