Chapter 33: Oligopoly (1.5)
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


Assumptions of the oligopoly model
Concentration ratio
Interdependence
Game theory; prisoners’ dilemma
Assumptions of
the model
Game theory

•
Describe, using examples, the assumed characteristics of
an oligopoly: the dominance of the industry by a small
number of firms; the importance of interdependence;
differentiated or homogeneous products and high barriers
to entry
•
Explain why interdependence is responsible for the
dilemma faced by oligopolistic firms whether to compete or
to collude
•
Explain how a concentration ratio may be used to identify
an oligopoly
•
Explain how game theory (the simple 2 by 2 prisoner’s
dilemma) can illustrate strategic interdependence and the
options available to oligopolies
Assumptions of the oligopoly model
An oligopoly has some key defining characteristics, namely that the market is dominated by a few large
firms and that potential entrants face high barriers to entry – the latter being a key difference to the
monopolistically competitive market. Furthermore, products can be both homogeneous and differentiated –
for example both cement (homogeneous) and breakfast cereals (differentiated) are oligopolistic markets.
With these outlining assumptions in place the oligopolistic market takes on a number of rather unique
features which subsequently define the market.

Concentration ratio
Standard economic theory defines an oligopolistic market as one where the four or five largest firms
control a major share of the market. This is the market concentration ratio, and is most frequently
calculated as the total sales of an individual firm divided by total market sales. The rule of thumb is that
when the four or five largest firms have over 30% of the market, an oligopoly situation is at hand.

Interdependence
A common denominator in oligopolistic markets is that there are very high barriers to entry, with wellestablished firms being able to heighten these barriers by using extensive advertising and branding to
dissuade potential entrants. This is accentuated by the sheer size of many oligopoly firms, which are able to
move along the LRAC curve and enjoy benefits of scale.
As a single firm will not have total control of the market but still be large enough to affect output and price,
firms will be acutely aware of each other and will make it their business to have a great deal of knowledge
about the others. This leads to a large degree of interdependence as each firm knows that any action on its
part will cause some form of reciprocal (= ‘in return’) action or reaction; ‘What goes around, comes
around’. This makes it very difficult to predict price and output outcomes, as we shall see.

Game theory; prisoners’ dilemma
Jack and Jill decide that carrying water up and down the hill is a waste of resources and decide to resort to
the old-fashioned method of theft1. They illegally siphon water from a nearby reservoir and ultimately the
‘leakage’ is noticed. The police arrest them on charges of grand-theft but have only enough evidence to
convict them of stealing a hose. The two are put into separate holding cells, all the while pleading their
innocence to the crime of water-siphoning, but admitting to the crime of stealing hoses. The hose theft
carries a two year jail sentence, and the interrogator knows that the prosecutor needs a confession to
convict them of the greater crime of water-siphoning. The two accused are unable to communicate.
The crafty interrogator makes the following offer – separately – to Jack and Jill: ‘We have evidence enough
to convict you for the theft of the hose, and put you each in jail for two years. However, we also know that
you are also guilty of siphoning water. If I get confessions from both of you, we will give you each two
years in a soft, minimum security prison. If one of you confesses while the other denies, the confessor will
get one year but the other will get a 10 year penalty where you will spend your days with rapists,
murderers, Ramstein fans and hardened criminals.’2
He then leaves the both of them to think over their options, which are:
1.
Cooperate and stick to denial! This will result in two years in prison for each of them.
2.
Confess and get a maximum of three years in prison.
As both Jack and Jill have two options each, there are four possible outcomes. Note that Jill ’s decision will
affect Jack’s outcome and vice versa! That is, the two are interdependent. Figure 2.3.46 shows the four
possible outcomes in a payoff matrix.
1I
2
am alluding to a childhood nursery rhyme; ‘Jack and Jill went up the hill to fetch a pail of water…’ and I forget
the rest.
Don’t send me angry letters – I’m a big Ramstein fan! Du Hast is playing as I write this.
Fig. 2.3.46 Payoff matrix for Prisoner’s Dilemma
Jack’s choices
Confess
Deny
3 years
10 years
Confess
Jill’s choices
3 years
1 year
1 year
2 years
Deny
10 years
2 years
Each one ponders away in his/her cell. The dilemma facing each of them is not knowing what the other will
do! Let’s look at Jill’s options. If she sticks to her denial, she can hope to have a maximum of two years in
prison – IF Jack also denies. Jill’s temptation to confess comes with the realization that Jack too is thinking
the same way. Thus, if Jill denies she runs the risk that Jack confesses, which lands Jill in prison for 10
years! The question both are asking themselves is ‘I don’t know what the other is going to do! Do I dare
deny and put my hopes in the other also denying?!’
Collusion – i.e. both denying – would produce the optimum total outcome of two years each, but the
problem is that Jack and Jill are not allowed to communicate. The best outcome for one of them is
confessing – cheating on each other – while the other denies. If both decide to minimize the impact of not
knowing what the other will do, then both will confess. The dilemma creates a movement towards the grey
box in the payoff matrix above, an outcome known as a Nash equilibrium, where each player has adopted a
strategy giving him/her the best possible outcome given the expected action of the other.
(Type 4 Smaller heading) The oligopolist’s dilemma
The line of thinking illustrated in the prisoner’s dilemma can be applied to oligopoly strategy. Consider two
oligopoly firms which have 100% of the market together, a duopoly. Posit that each firm initially is making
a normal profit. Each firm wants to increase its profit and looks at the options. By raising the price in
concert (collusion) both firms might make an abnormal profit as they would be acting as a monopoly.
However, Firm A could stand to lose customers and profit if Firm B keeps the same price. If Firm A lowers
the price it could make an abnormal profit – or the action could force Firm B to also lower the price and
both lose! The final uncertainty of the other’s action could force each firm into doing nothing – which
would then be the best decision taking into account the expected action of the other – there would be a
Nash equilibrium.
I have taken great artistic license and grossly oversimplified the use of game theory in the preceding
example, and I am bending the syllabus boundaries as it is. There are many possible outcomes in a
‘duopoly game’, since the game would not be a ‘one shot only’ game such as portrayed in the prisoner’s
dilemma. Firm A will face the knowledge that firm B could retaliate A’s price by lowering their price,
leading to re-retaliation (?!) by A… and a price war results which is harmful to both firms. The outcome is
most uncertain. Non-collusive oligopoly is often characterized by brief spells of competitive flurries yet
broad price rigidity.
x
Summary and revision (need a cool pic here….maybe a pic of someone doing pushups!)
1. The assumptions for an oligopoly are that the market is dominated by a few large
firms on a market with high barriers to entry. Goods can be both homogenous and
differentiated.
2. Market concentration is measured by a four- or five-firm concentration ratio.
This measures the total market share of the four or five largest firms as a
percentage of total sales in the industry.
3. The four or five major firms in an oligopoly are interdependent – e.g. the actions
of one large firm in terms of pricing and/or product differentiation will cause a
counteraction by the other main firms.
4. Game theory attempts to explain the possible strategic options available to firms
operating under interdependent conditions. The most famous example is the
Prisoners’ Dilemma.
Chapter 34: Collusive and non-collusive oligopoly
(1.5)
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
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Open collusion (cartels) and tacit (informal) collusion
Non-collusive oligopoly
The importance of non-price competition
Open/formal collusion
•
Explain the term “collusion”, give examples, and state that it is usually (in most
countries) illegal
•
•
•
Explain the term “cartel”
Explain that the primary goal of a cartel is to limit competition between member
firms and to maximize joint profits as if the firms were collectively a monopoly
Explain the incentive of cartel members to cheat as well as the conditions
making cartel structures difficult to maintain
•
Explain the incentive of cartel members
•
Analyse the conditions which make cartel structures difficult to maintain
Tacit/informal
collusion
•
Non-collusive oligopoly
•
•
•
•
Describe the term “tacit collusion” including reference to price
leadership by a dominant firm
Explain that the behaviour of firms in a non-collusive oligopoly is strategic in
order to take account of possible actions by rivals
Explain, using a diagram, the existence of price rigidities with reference to the
kinked demand curve (don’t discuss economics over vodka!)
Explain why non-price competition is common in oligopolistic markets, with
reference to the risk of price wars
Describe, using examples, types of non-price competition
The two paths the firms in the example can go by are basically to collude or compete (a non-collusive
oligopoly). They could also simply do nothing! This is not as silly as it might sound. In the long run, either
of the options will lead to a degree of price rigidity. Let us look at each option in turn.
Definition: collusive and non-collusive oligopolies
A collusive oligopoly is when firms in an oligopoly market collude (cooperate) on prices,
output or sales venues in order to maximise profits. If oligopoly firms instead compete
independently one speaks of a non-collusive oligopoly.

Open collusion (cartels) and tacit (informal) collusion
1) Open (overt) collusion: If the main actors on the oligopoly instead have a formal agreement as to
price and/or output, then collusion is open (sometimes called overt). This is basically a cartel and
most countries have strict regulations against this type of competition-limiting behaviour;
basically open collusion is illegal.3 (See Case study: Unhealthy cartel below.)
2) Tacit (covert) collusion: There could be tacit (= unspoken) collusion where there is a price leader
that the rest follow, or firms could follow benchmark prices such as recommended prices set down
(legally!) by a producer organisation. Firms which have similar cost pictures could use the same
mark-up (as in cost-plus pricing) and arrive at the same price level.
In any shape or form, collusion tends to move the market towards a monopoly outcome with very little
price fluctuation as the price is more a result of agreement than market forces.
(Type 4 Smaller heading) Ways of collusion
Firms have quite a few options when it comes to colluding, the most common forms being:

Setting the price is perhaps the most common method, yet there are many other ways to lower the
competitive forces which harm oligopolist’s profit. (Pharmaceutical companies)
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Dividing the market into regions basically creates regional monopolies. (Glass companies in the
EU)

Agreeing on quotas will limit supply and drive up the market price. (OPEC)
A collusive agreement taken to the extreme results in a cartel. A cartel acts to increase profits by
setting/controlling output, or price, by dividing the market up between firms. The most famous cartels
today are de Beers diamond cartel and the Organisation of Petroleum Exporting Countries – better known
as OPEC.
Cartels are notoriously difficult to uphold and maintain. The primary reason has been given earlier; the
temptation for members to cheat, knowing that the arrangement is illegal in the first place and in the second
place that one can earn additional profits at the expense of the others. 4 It is also hard to get all members to
agree to a common set of quotas and/or prices, as these will be set with the common good in mind rather
than that of an individual firm.

Non-collusive oligopoly
One way to illustrate the aforementioned outcome of price rigidity in non-collusive oligopoly situations is
the kinked demand curve5. Consider a firm operating in an oligopolistic market, where a non-collusive
price is (somehow) arrived at; PEQ in figure 2.3.47 below. Just as in the prisoner’s dilemma, the firm is in a
highly interdependent situation, where a change in price will certainly lead to a reaction from other firms in
the oligopoly. The model suggests the individual firm will arrive at the following; ‘If I raise my price
nobody will follow since they will expect to steal my customers. If I lower my price everybody will follow
3
There is some seriously scary reading available at http://ec.europa.eu/competition/cartels/cases/cases.html
Basically you need to be some kind of stupid to take notes of meetings, keep logs and put to paper/email
all the activities and agreements involved in keeping up an illegal cartel. This is gleefully enough exactly
what happened in 2007, when the European Commission found brewers Heineken, InBev, Grolsch and
Bavaria guilty of running an illegal cartel for beer in The Netherlands during the period 1996 - 1999.
Ample evidence of hand-written notes from meetings provided the basis for the verdict – and a rather hefty
fine of €273 million (circa USD360 million at the time) for the brewers. I wonder if the brewers were
perhaps…inebriated.
4
5Not
‘kinky’ but kinked, meaning ‘bent’.
in order to hinder me from stealing their customers!’ Plotting this out in figure 2.3.47:

A higher price will cause a proportionally larger decrease in revenue for the firm and thus the
demand curve will be elastic above the starting equilibrium price of PEQ. The firm would lose
market share to other firms by raising the price.

In lowering the price, a firm would quickly be followed by competitors who themselves would
fear losing sales to the price-lowering firm. Therefore any decrease in price below PEQ would
mean a more inelastic demand curve and a decrease in revenue.
The demand curve will be ‘kinked’ at the point of equilibrium price and output, and as the MR curve is
dependent on the shape of the demand curve, the MR curve is discontinued. 6
6
The issue of what the MR curve should look like in the kinked demand curve is subject to heated discussion. When
the first edition came out, my friend Alan “Gandalf” Hobson immediately took issue with the fact that I’d left a portion
of the lower part of the MR curve above the Q-axis – while claiming that the relevant portion of the demand curve was
inelastic. Alan, I’ve thought it through. You are right. Another discussion took place during the Oxford Revision
Courses in 2010 when I had a furious discussion with my dear friend George…in a pub in front of some pretty terrified
colleagues. The lesson is; NEVER discuss economics over Vodka! My other dear colleague Konstantin has since made
sure that he doles out the Stolichnaya a bit more sparingly. Yes, it was your fault Konstantin.
Fig. 2.3.47 Kinked demand curve
The kink in the demand curve means that the MR curve will be
discontinuous – broken.
P, costs ($)
The dotted extensions of the curves are only to show how each
MR curve will cut “halfway” on the Q-axis. (Don’t include
these in your own diagrams!)
Elastic
demand
Inelastic demand (note that since only the inelastic portion of the
D-curve is used, MR will be negative)
PEQ
D, AR
MR
QEQ
Q/t
D, AR
MR
P, costs ($)
MC0
The broken MR curve enables a range of
possible MC = MR points. The diagram shows
that marginal costs can change without the
oligopolist having to change output in order to
stay at the profitmax level of output.
MC1
QEQ
MC2
D, AR
QEQ
Q/t
MR
The model of the kinked demand curve helps to explain two key characteristics of oligopolistic markets:
1) Why oligopolies have a tendency towards price rigidity. The ‘kink’ in the demand curve is the
same situation as in the prisoner’s dilemma; a Nash equilibrium, where each firm’s decision to
leave the price untouched is actually the best outcome for the firm – as long as all the other firms
act the same!
2) Why oligopolies so often do not compete in price but rather resort to various forms of non-price
competition. (See next heading.) Any form of price competition amongst the few large firms
controlling the market can well lead to price wars – e.g. where one competitor lowers prices and
others retaliate by lowering even further…creating a downward price spiral which ultimately only
leaves one winner; the consumer.

The importance of non-price competition
(Type 3 Medium heading) Quality and innovation
In an argument similar to that in the monopoly model, large oligopoly firms could well have large
abnormal profits available for R&D, quality enhancement and innovative new products. Using, once again,
my passion for wristwatches as a starting point, Rolex has a long history of innovation; patenting of the
perpetual motion mechanism (a self-winding watch mechanism); the famous ‘Oyster case’ was made in
1926 thereby creating the worlds’ first truly water-proof watch; a date was added in 1945, resulting in the
Date-just watch (virtually unchanged today it is probably the most recognised watch in the world); the
Submariner watch became the first diving watch in the late 1950s and so forth. The latest version of the
Rolex Sea-Dweller (“Deep Sea”) is waterproof to…wait for it; 3,900 metres7! Yes, it’s on my wrist as I
write this.
(Type 3 Medium heading) Enhancing perceived value
One of the world’s most famous marketers, Philip Kotler, uses a model of ‘Core, tangible and augmented
product’ to explain how firms can develop a product’s profile8. A firm in non-price competition will seek
to add to the perceived value in consuming the good by focusing on many possible intangible aspects – the
‘feel’ of the good.
Basically the producer attempts to ‘augment’ (= increase, amplify) the buyer’s sense of benefit by stressing
the additional post-purchase value of the good; BMW has free service for the first three years and Cadillac
has a 24 hour breakdown service including towing, repairs, and replacement vehicle.
(Type 3 Medium heading) Branding and advertising
Volvo sells cars using the ‘safety’ argument; Toyota is ‘reliable and economical’; while BMW uses
‘performance’ – these marketing efforts serve to differentiate the products and at the same time limit the
degree of head-to-head competition.
‘What’s in a name!?’ goes an old saying. The answer in connection with branding is ‘A lot! ’ Brands have
become increasingly valuable assets for firms. For example, Interbrand – a renowned branding consultancy
firm – values the above-mentioned Rolex brand at close to $5 billion. The top three global names in term of
brand value in 2008 were Coca Cola ($66.6 billion), Microsoft ($59 billion) and IBM ($59 billion).9
(Type 4 Smaller heading) And yet the small survive
In view of the on-going process where (global) oligopolies arise, how do so many small firms manage to
remain? Part of the answer is to be found in human nature. People tend to feel comfortable with the close
and familiar, so a local fast food place will have its place in spite of any number of international chains. It
also makes it easier to get additional service, say in repairs or follow-up service – anyone who’s bought a
bicycle knows the value of local service! Another reason for small scale success is that many services do
not easily benefit from scale, for example haircuts, shoe repairs and garden services. Finally, local tastes,
customs and preferences make large scale ‘streamlining’ more difficult for large firms and also give
small/local firms an edge in quickly adapting to changes in local tastes. In short, it is a challenge for firms
to be both global and local.
7www.rolex.com
and Wristwatches pages 350 - 361; Brunner, Gisbert L. and Pfeiffer-Belli, Christian, Germany,
1999, ISBN 3-8290-0660-8
8Kotler, Philip; Marketing management, Prentice-Hall International Editions, 1988, sixth edition; ISBN 0-13556267-8
9
http://www.interbrand.com/best_global_brands.aspx
Summary and revision
5. A collusive oligopoly is a market situation where oligopoly firms cooperate by way
of setting prices, output or dividing the market between them.
6. A non-collusive oligopoly is a market situation where oligopoly firms compete and
each firm is acutely aware of the other firms’ actions – there is a high degree of
interdependency.
7. Open collusion is when firms form a cartel, e.g. a formal organisation formed by
firms in order to set price, output or in other ways manage the market.
8. Tacit collusion is when firms follow a “price leader” or some form of benchmark
prices rather than a formalised pricing structure.
9. Open collusion can be done by agreeing on the price, setting output quotas, and
dividing the market up geographically.
10. Oligopolies are often characterised by price rigidity and non-price competition.
The kinked demand curve helps explain this to a certain extent.
11. Methods of non-price competition include focusing on R&D and innovation,
enhancing perceived value and branding via heavy advertising.