Final answer:
The A. C. Nielsen Co. is the source for network television and local audience information, with local stations that broadcast national network programming known as affiliates. These affiliates, integrated with networks like ABC, CBS, NBC, and Fox, have historically shaped viewing options in the U.S.
Step-by-step explanation:
The sole source of network television and local audience information is the A. C. Nielsen Co., widely known for its television ratings. A local station that broadcasts national network programming is called an affiliate. These affiliates are typically aligned with national networks, such as ABC, CBS, NBC, and Fox, which supply most of their programming. This system has been prevalent since the inception of television broadcasting, where networks and their affiliates have been fundamental in shaping what people watch and listen to across the United States.
During the early days of television, most programs were sponsored by a single advertiser with product placements integrated directly into the show. As the industry evolved, commercial breaks replaced direct product placements, and by the 1980s, cable networks began challenging the dominance of over-the-air broadcast networks. Throughout the years, national networks have relied on their local affiliates to extend their reach and maintain relevance throughout the country. As technology progresses, the trend is moving from mass broadcasting to 'narrowcasting', allowing viewers greater choice in selecting media content that aligns with their personal interests.