Source
Top US media companies and marketers are working on their own consortium to break the grip of the dominant force in the TV audience measurement business. Media participants including networks owned by NBC Universal, Time Warner, News Corp, Viacom, CBS, Discovery and Disney are frustrated by the glacial pace of development in the critical business of counting viewers in the digital age.
It mentions in the article that 18,000 homes are part of the Nielsen ratings, out of a U.S. population of 300 million. That's an insanely low sampling for such a large country.
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