A TV broadcaster has a "duopoly" if it owns two television stations within the same market. A situation in which one broadcaster owns three TV stations in the same market would be called a "triopoly." The FCC regulates broadcasters' ability to have duopolies: The TV market, or DMA, must have eight remaining independent TV-station owners once any duopoly is completed (a provision known as "the eight-voice test"); and no single company may own two of the market's top-four stations as ranked by Nielsen audience ratings (in most larger markets, typically stations owned by or affiliated with ABC, CBS, NBC and FOX), unless one of those stations is deemed to be a failing business. As with Cross-Ownership, broadcasters have sought a relaxation of Duopoly restrictions.
Any marketplace where consumer choice is limited to two service providers. In the broadband world, duoply applies to the cable and DSL services that today control almost 98 percent of the residential and small-business broadband market.
A true duopoly is a form of oligopoly where only two producers exist in a market. In reality, this definition is generally eased whereby two firms must only have dominant control over a market. In the field of industrial organization, it is the most commonly studied form of oligopoly due to its simplicity.