Abstract: Methods and apparatus to de-duplicate impression information are disclosed. An example method to de-duplicate media impression information includes determining an overlap between cookies of a first database proprietor and cookies of a second database proprietor on client computers; determining duplicate impression information based on first impression information associated with the first database proprietor, second impression information associated with the second database proprietor, and the overlap; and determining unduplicated impression information based on the duplicate impression information, the first impression information, and the second impression information.

Abstract: A disclosed example method to determine audience duplication in cross-media campaigns involves determining a first duplicated audience reach for a demographic group between a total television audience and an internet publisher audience. The total television audience is representative of audience members across a plurality of television networks. The internet publisher audience is representative of audience members of one of a plurality of internet publishers. The example method involves determining a second duplicated audience reach between the total television audience and the internet publisher audience for a media campaign based on the first duplicated audience reach. The example method involves determining a third duplicated audience reach between a television network audience and the internet publisher audience for the media campaign based on the second duplicated audience reach.

Abstract: A disclosed example method to determine audience duplication in cross-media campaigns involves determining a first duplicated audience reach between a total television audience and an internet publisher audience for a demographic group. The total television audience is representative of audience members across a plurality of television networks, and the internet publisher audience is representative of audience members across one of a plurality of internet publishers. The example method involves determining a second duplicated audience reach between the total television audience and the internet publisher audience for a media campaign based on the first duplicated audience reach. The example method involves determining a third duplicated audience reach between a television network audience and the internet publisher audience for the media campaign based on the second duplicated audience reach.