<Table> <Tr> <Td> </Td> <Td> This list needs additional citations for verification . Please help improve this article by adding citations to reliable sources . Unsourced material may be challenged and removed . (January 2015) (Learn how and when to remove this template message) </Td> </Tr> </Table> <Tr> <Td> </Td> <Td> This list needs additional citations for verification . Please help improve this article by adding citations to reliable sources . Unsourced material may be challenged and removed . (January 2015) (Learn how and when to remove this template message) </Td> </Tr> <P> In the United States, for most of the history of broadcasting, there were only three or four major commercial national broadcast networks . From 1946 to 1956, these were ABC, CBS, NBC and DuMont (though the Paramount Television Network had some limited success during these years). From 1956 to 1986, the "Big Three" national commercial networks were ABC, CBS, and NBC (with a few limited attempts to challenge them, such as National Telefilm Associates (and its NTA Film Network) and the Overmyer Network). From 1954 to 1970, National Educational Television was the national clearinghouse for public TV programming; the Public Broadcasting Service (PBS) succeeded it in 1970 . </P> <P> Today, more than fifty national broadcasting networks exist . Other than the non-commercial educational (NCE) PBS, which is composed of member stations, the largest broadcast television networks are the traditional Big Three television networks (ABC, CBS and NBC). Many other large networks exist, however, notably Fox and The CW which air original programming for two hours each night instead of three like the original "Big Three" do, as well as syndication services like MyNetworkTV and Ion Television which feature reruns of recent popular shows with little to no original programming . Fox has just about the same household reach percentage as the Big Three, and is therefore often considered a peer to ABC, NBC, and CBS since it has also achieved equal or better ratings since the late 1990s . Most media outlets now include Fox in what they refer to as the "Big Four" TV networks . </P>

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