Oligopoly

The meaning of oligopoly, and why it occurs
Why oligopolists have an incentive to act in ways that reduce their combined profit, and why they can benefit from collusion
How our understanding of oligopoly can be enhanced by using game theory, especially the concept of the prisoners’ dilemma
How repeated interactions among oligopolists can help them achieve tacit collusion
How oligopoly works in practice, under the legal constraints of antitrust policy

The Prevalence of Oligopoly
In addition to perfect competition and monopoly, oligopoly and monopolistic competition are also important types of market structure. They are forms of imperfect competition.

The Prevalence of Oligopoly
Oligopoly is a common market structure.
It arises from the same forces that lead to monopoly, except in weaker form.
It is an industry with only a small number of producers.
A producer in such an industry is known as an oligopolist.

The Prevalence of Oligopoly
When no one firm has a monopoly, but producers nonetheless realize that they can affect market prices, an industry is characterized by imperfect competition.

Some Oligopolistic Industries

Understanding Oligopoly
Some of the key issues in oligopoly can be understood by looking at the simplest case, a duopoly.
An oligopoly consisting of only two firms is a duopoly. Each firm is a duopolist.
With only two firms in the industry, each would realize that by producing more, it would drive down the market price. So each firm would, like a monopolist, realize that profits would be higher if it limited its production.

Understanding Oligopoly
One possibility is that the two companies will engage in collusion. Sellers engage in collusion when they cooperate to raise each others’ profits.
The strongest form of collusion is a cartel, an agreement by several producers to obey output restrictions in order to increase their joint profits.
They may also engage in non-cooperative behavior, ignoring the effects of their actions on each others’ profits.

Understanding Oligopoly
By acting as if they were a single monopolist, oligopolists can maximize their combined profits. So there is an incentive to form a cartel.
However, each firm has an incentive to cheat—to produce more than it is supposed to under the cartel agreement. So there are two principal outcomes: successful collusion or behaving non-cooperatively by cheating.
When firms ignore the effects of their actions on each others’ profits, they engage in non-cooperative behavior. It is likely to be easier to achieve informal collusion when firms in an industry face capacity constraints.

Competing in Prices vs. Competing in Quantities
Firms may decide to engage in quantity or price competition.
The basic insight of the quantity competition
(or the Cournot model) is that when firms are restricted in how much they can produce, it is easier for them to avoid excessive competition and to “divvy up” the market, thereby pricing above marginal cost and earning profits.
It is easier for them to achieve an outcome that looks like collusion without a formal agreement.

Competing in Prices vs. Competing in Quantities
The logic behind the price competition (or the Bertrand model) is that when firms produce perfect substitutes and have sufficient capacity to satisfy demand when price is equal to marginal cost, then each firm will be compelled to engage in competition by undercutting its rival’s price until the price reaches marginal cost—that is, perfect competition.

The Prisoners’ Dilemma
When the decisions of two or more firms significantly affect each others’ profits, they are in a situation of interdependence.
The study of behavior in situations of interdependence is known as game theory.
The reward received by a player in a game—such as the profit earned by an oligopolist—is that player’s payoff.
A payoff matrix shows how the payoff to each of the participants in a two player game depends on the actions of both. Such a matrix helps us analyze interdependence.

A Payoff Matrix
ADM
Ajinomoto
Produce 30 million pounds
ADM makes $180 million profit
Produce 40 million pounds
Produce 30 million pounds
Produce 40 million pounds
Ajinomoto makes $180 million profit.
Ajinomoto makes $200 million profit.
Ajinomoto makes $160 million profit.
Ajinomoto makes $150 million profit.
ADM makes $150 million profit
ADM makes $200 million profit
ADM makes $160million profit

The Prisoners’ Dilemma
Economists use game theory to study firms’ behavior when there is interdependence between their payoffs. The game can be represented with a payoff matrix. Depending on the payoffs, a player may or may not have a dominant strategy.
When each firm has an incentive to cheat, but both are worse off if both cheat, the situation is known as a prisoners’ dilemma.
The game based on two premises: (1) Each player has an incentive to choose an action that benefits itself at the other player’s expense. (2) When both players act in this way, both are worse off than if they had acted cooperatively.

The Prisoners’ Dilemma
Don’t confess
Don’t confess
Confess
Confess
Louise
Louise gets 2-year sentence.
Louise gets 5-year sentence.
Thelma gets 20-year sentence.
Thelma gets 5-year sentence.
Louise gets 15-year sentence.
Louise gets 20-year sentence.
Thelma gets 15-year sentence.
Thelma gets 2-year sentence.
Thelma

The Prisoners’ Dilemma
An action is a dominant strategy when it is a player’s best action regardless of the action taken by the other player. Depending on the payoffs, a player may or may not have a dominant strategy.
A Nash equilibrium, also known as a non-cooperative equilibrium, is the result when each player in a game chooses the action that maximizes his or her payoff given the actions of other players, ignoring the effects of his or her action on the payoffs received by those other players.

Overcoming the Prisoners’ Dilemma
Repeated Interaction and Tacit Collusion
Players who don’t take their interdependence into account arrive at a Nash, or non-cooperative, equilibrium. But if a game is played repeatedly, players may engage in strategic behavior, sacrificing short-run profit to influence future behavior. In repeated prisoners’ dilemma games, tit for tat is often a good strategy, leading to successful tacit collusion.
Tit for tat involves playing cooperatively at first, then doing whatever the other player did in the previous period.
When firms limit production and raise prices in a way that raises each others’ profits, even though they have not made any formal agreement, they are engaged in tacit collusion.

How Repeated Interaction Can Support Collusion
Tit for tat
Tit for tat
Always cheat
Always cheat
ADM
Ajinomoto
ADM makes $180 million profit each year.
Ajinomoto makes $180 million profit each year.
Ajinomoto makes $200 million profit 1st year, $160 profit each later year.
Ajinomoto makes $150 million profit 1st year, $160 million profit each later year.
Ajinomoto makes $160 million profit each year.
ADM makes $150 million profit 1st year, $160 million profit each later year.
ADM makes $200 million profit 1st year, $160 million profit each later year.
ADM makes $160 million profit each year.

The Kinked Demand Curve
An oligopolist who believes she will lose a substantial number of sales if she reduces output and increases her price, but will gain only a few additional sales if she increases output and lowers her price away from the tacit collusion outcome, faces a kinked demand curve—very flat above the kink and very steep below the kink.
It illustrates how tacit collusion can make an oligopolist unresponsive to changes in marginal cost within a certain range when those changes are unique to her.

The Kinked Demand Curve
Q
*
P
*
Quantity
Price, cost marginal revenue
X
W
Y
D
Z
MR
MC
2
MC
1
1. Any marginal cost in this region
2. … corresponds to this level of output
Tacit collusion outcome

The Ups and Downs of the Oil Cartel
60
$70
50
40
30
20
10
Price of crude oil (per barrel)
Year
Crude Oil Prices, 1947-2007
(in constant 2006 dollars)
1947
1950
1960
1970
1980
1990
2000
2007
Iran-Iraq War
9/11/01
Gulf War
Iranian Revolution
Rising world demand and Middle East tensions
Yom Kippur War Arab Oil Embargo
Series of OPEC output cuts
OPEC 10% quota increase

Oligopoly in Practice
Oligopolies operate under legal restrictions in the form of antitrust policy. Antitrust policies are efforts undertaken by the government to prevent oligopolistic industries from becoming or behaving like monopolies. But many succeed in achieving tacit collusion.
Tacit collusion is limited by a number of factors, including:
large numbers of firms
complex products and pricing scheme
bargaining power of buyers
conflicts of interest among firms

Product Differentiation and Price Leadership
When collusion breaks down, there is a price war.
To limit competition, oligopolists often engage in product differentiation which is an attempt by a firm to convince buyers that its product is different from the products of other firms in the industry.
When products are differentiated, it is sometimes possible for an industry to achieve tacit collusion through price leadership.
Oligopolists often avoid competing directly on price, engaging in non-price competition through advertising and other means instead.

Product Differentiation and Price Leadership, cont’d
In price leadership, one firm sets its price first, and other firms then follow.
Firms that have a tacit understanding not to compete on price often engage in intense nonprice competition, using advertising and other means to try to increase their sales.

Many industries are oligopolies: there are only a few sellers. In particular, a duopoly has only two sellers. Oligopolies exist for more or less the same reasons that monopolies exist, but in weaker form. They are characterized by imperfect competition: firms compete but possess market power.
Predicting the behavior of oligopolists poses something of a puzzle. The firms in an oligopoly could maximize their combined profits by acting as a cartel, setting output levels for each firm as if they were a single monopolist; to the extent that firms manage to do this, they engage in collusion. But each individual firm has an incentive to produce more than it would in such an arrangement—to engage in noncooperative behavior.

The situation of interdependence, in which each firm’s profit depends noticeably on what other firms do, is the subject of game theory. In the case of a game with two players, the payoff of each player depends both on its own actions and on the actions of the other; this interdependence can be represented as a payoff matrix. Depending on the structure of payoffs in the payoff matrix, a player may have a dominant strategy—an action that is always the best regardless of the other player’s actions.

Duopolists face a particular type of game known as a prisoners’ dilemma; if each acts independently in its own interest, the resulting Nash equilibrium or Noncooperative equilibrium will be bad for both. However, firms that expect to play a game repeatedly tend to engage in strategic behavior, trying to influence each other’s future actions. A particular strategy that seems to work well in such situations is tit for tat, which often leads to tacit collusion.
The kinked demand curve illustrates how an oligopolist that faces unique changes in its marginal cost within a certain range may choose not to adjust its output and price in order to avoid a breakdown in tacit collusion.