In the United States, Federal Communications Commission (FCC) regulations limit the number of network-owned stations as a percentage of total national market reach.
For instance, Mission Broadcasting's WPIX serves as the New York City affiliate of The CW (which is 75% owned by station operator Nexstar Media Group, with Warner Bros.
A similar rule exists in Japan, in which regulations governed by the Ministry of Internal Affairs and Communications limit the number of network-owned commercial television stations as a percentage of total national market reach.
As such, commercial networks tend to have O&Os only in the four largest media markets (Kantō, Keihanshin, Chūkyō, and Fukuoka), and rely on affiliates to carry their programming in other prefectures.
As such, most television stations, regardless of market size, are now O&Os of their respective networks, with only a few true affiliates remaining (mainly located in smaller cities).
The Canadian Broadcasting Corporation originally relied on a large number of privately owned affiliates to disseminate its radio and television programming.
While network-owned stations will normally carry the full programming schedule of the originating network (save for major local events), an affiliate is independently owned and typically under no obligation to do so.
In some markets, the network maintains memberships with two noncommercial educational stations – in some cases, these are owned by the same entity – which split the programming rights.
The digital conversion allowed KXGN to carry CBS and NBC programming side-by-side on separate subchannels, essentially becoming a primary affiliate of both networks.
These may be supplemented by LPTV or repeater stations to allow more channels to be added without encountering federally imposed limits on concentration of media ownership.
Often, the multiple commonly controlled stations will use the same news and local advertising sales operations, but carry different network feeds.
Another example is WBKB-TV in Alpena, Michigan, owned by The Marks Group, which also carries CBS programming on its main signal and both Fox and MyNetworkTV on its second digital subchannel.
CJON-DT in St. John's, Newfoundland, nominally an independent station, uses this model to acquire programming from CTV and the Global Television Network.
CJNT-DT in Montreal formerly maintained dual affiliations through both City and Omni Television to satisfy its ethnic programming requirements due to its sale to Rogers Media in 2012.
From September 1, 2016, to August 31, 2019, the largest current-day market example of a dual affiliation was with Fox Television Stations's WPWR-TV, a Gary, Indiana-licensed station serving the entire Chicago market, which carried a primary affiliation with The CW, while maintaining Fox's MyNetworkTV programming service in a late night timeslot.