What competition model assumes firms choose output levels simultaneously?

The competition model in which firms choose output levels simultaneously is Cournot competition.

In the Cournot model, competing firms decide how much of a usually homogeneous product to produce, taking rivals’ quantities as given. The market price is then determined by total output and demand. Each firm chooses the quantity that maximizes its profit in response to the quantities it expects from the others. When every firm’s choice is a best response to the others, the result is a Cournot-Nash equilibrium.

Antoine Augustin Cournot introduced the model in his 1838 book Recherches sur les Principes Mathématiques de la Théorie des Richesses. He used a spring-water duopoly as an example: two suppliers select quantities, and the market-clearing price depends on their combined production. Cournot’s work helped establish the mathematical study of oligopoly.

The main distinction is the strategic variable. Bertrand competition assumes firms compete by choosing prices, while Stackelberg competition gives one firm a first-mover advantage in choosing output before the follower acts. Monopolistic competition instead describes many firms selling differentiated products, not a specific simultaneous-quantity game. Real markets may depart from Cournot assumptions when firms collude, products differ, or decisions occur sequentially.