A duopoly (from Greek δύο, duo "two" and πωλεῖν, polein "to sell") is a type of oligopoly where two firms have dominant or exclusive control over a market. It is the most commonly studied form of oligopoly due to its simplicity. Duopolies sell to consumers in a competitive market where the choice of an individual consumer can not affect the firm. The defining characteristic of both duopolies and oligopolies is that decisions made by sellers are dependent on each other.

one two few
sellers monopoly duopoly oligopoly
buyers monopsony duopsony oligopsony

Duopoly models in economics and game theory

There are two principal duopoly models, Cournot duopoly and Bertrand duopoly:

  • The Cournot model, which shows that two firms assume each other's output and treat this as a fixed amount, and produce in their own firm according to this.
  • The Bertrand model, in which, in a game of two firms, each one of them will assume that the other will not change prices in response to its price cuts. When both firms use this logic, they will reach a Nash equilibrium.

Characteristics of duopoly

  1. Existence of only two sellers
  2. Interdependence: if any firm makes the change in the price or promotional scheme, other firms also have to comply with it, to remain in the competition.[further explanation needed]
  3. Presence of monopoly elements: so long as products are differentiated, the firms enjoy some monopoly power, as each product will have some loyal customers
  4. There are two popular models of duopoly, i.e., Cournot's Model and Bertrand's Model.


Like a market, a political system can be dominated by two groups, which exclude other parties or ideologies from participation. One party or the other tends to dominate government at any given time (the Majority party), while the other has only limited power (the Minority party). According to Duverger's law, this tends to be caused by a simple winner-take-all voting system without runoffs or ranked choices. The United States and many Latin American countries, such as Costa Rica, Guyana, and the Dominican Republic have two-party government systems.

Examples in business

A commonly cited example of a duopoly is that involving Visa and MasterCard, who between them control a large proportion of the electronic payment processing market. In 2000 they were the defendants in a U.S. Department of Justice antitrust lawsuit.[1][2] An appeal was upheld in 2004.[3]

Examples where two companies control a overwhelming proportion of a market are:


In Finland, the state-owned broadcasting company Yleisradio and the private broadcaster Mainos-TV had a legal duopoly (in the economists' sense of the word) from the 1950s to 1993. No other broadcasters were allowed. Mainos-TV operated by leasing air time from Yleisradio, broadcasting in reserved blocks between Yleisradio's own programming on its two channels. This was a unique phenomenon in the world. Between 1986 and 1992 there was an independent third channel but it was jointly owned by Yle and MTV; only in 1993 did MTV get its own channel.

In the United Kingdom, the BBC and ITV formed an effective duopoly (with Channel 4 originally being economically dependent on ITV) until the development of multichannel from the 1990s onwards.

In Africa, mobile service providers Safaricom and Airtel in Kenya are examples of a Duopoly market in the telecommunication industry.


Duopoly is also used in the United States broadcast television and radio industry to refer to a single company owning two outlets in the same city.

This usage is technically incompatible with the normal definition of the word and may lead to confusion, inasmuch as there are generally more than two owners of broadcast television stations in markets with broadcast duopolies. In Canada, this definition is therefore more commonly called a "twinstick".

See also


  1. ^ "Complaint - ATR - Department of Justice". www.usdoj.gov. Retrieved 9 April 2018.
  2. ^ "Credit Card Antitrust Suit". mit.edu. Retrieved 9 April 2018.
  3. ^ "Amex is suing Visa and Mastercard". 15 November 2004. Retrieved 9 April 2018 – via news.bbc.co.uk.
  4. ^ 99.6 percent of new smartphones run Android or iOS. The Verge. 16 February 2017.
  5. ^ "Mobile Operating System Market Share Worldwide". StatCounter Global Stats. Retrieved 2020-06-12.
  6. ^ Galloway, Scott (2020). Post corona : from crisis to opportunity. New York, NY. p. 29. ISBN 9780593332214. The Google-Facebook duopoly's share of the digital ad market is predicted at 61% in 2021.
  7. ^ Kramer-Miller, Ben (June 25, 2013). "Norfolk Southern Corp. Looks Like A Solid Investment". Seeking Alpha. Retrieved October 7, 2014.