Slides 6
(Chapter 11)
2
Review: Cournot competition
Two firms that compete in quantities (BP is firm 1
and Shell is firm 2).
Select production to maximize profits, taking as
given the decision of the other firm
Linear demand 𝑃 𝑞1,𝑞2 = 𝑎 − 𝑏(𝑞1 + 𝑞2)
Same linear cost 𝐶 𝑞𝑖 = 𝑐𝑞𝑖 for 𝑖 = 1,2
Equilibrium and Profits
𝑞1
∗ = 𝑞2
∗=
𝑎−𝑐
3𝑏
𝑄𝐶 = 2(a − c)/3b and 𝑃𝐶 = 𝑎/3 + 2c/3
The profits of the firms are
𝜋1 = 𝜋2 = (𝑎 − 𝑐)
2/9𝑏
4
Stackelberg competition
Two firms (BP is firm 1 and Shell is firm 2)
BP is the leader and Shell is the follower
Select production to maximize profits
BP chooses 𝑞1 first
Shell sees the choice of BP, then chooses 𝑞2
Linear demand 𝑃 𝑞1,𝑞2 = 𝑎 − 𝑏(𝑞1 + 𝑞2)
Same linear cost 𝐶 𝑞𝑖 = 𝑐𝑞𝑖 for 𝑖 = 1,2
5
How do we solve this problem?
We solve the problem by backward induction
We start with the decision of the follower
We then figure out the choice of the leader
What firm makes more profits?
6
Problem of the follower
The profits of Shell (the follower) are
𝜋2 𝑞1, 𝑞2 = 𝑎 − 𝑏 𝑞1 + 𝑞2 𝑞2 − 𝑐𝑞2
The First Order Condition (FOC) is
𝜕𝜋2 𝑞1,𝑞2
𝜕𝑞2
= 𝑎 − 2𝑏𝑞2 − b𝑞1 − c = 0
Thus, 𝑞2 𝑞1 = (𝑎 − 𝑐 − 𝑏𝑞1)/2𝑏
7
Problem of the leader
The profits of BP (the leader) are
𝜋1 𝑞1, 𝑞2 = 𝑎 − 𝑏 𝑞1 + 𝑞2 𝑞1 𝑞1 − 𝑐𝑞1
Using the fact that 𝑞2 𝑞1 = (𝑎 − 𝑐 − 𝑏𝑞1)/2𝑏
𝜋1 𝑞1,𝑞2 = 𝑎 + 𝑐 − 𝑏𝑞1 /2 𝑞1 − 𝑐𝑞1
Thus, the FOC is
𝜕𝜋1 𝑞1, 𝑞2
𝜕𝑞1
=
𝑎 − 𝑐
2
− 𝑏𝑞1 = 0
Equilibrium and profits
BP will produce 𝑞1
∗ =
𝑎−𝑐
2𝑏
Shell will produce 𝑞2
∗=
𝑎−𝑐−𝑏𝑞1
∗
2𝑏
=
𝑎−𝑐
4𝑏
𝑄𝑆 = 3(a − c)/4b and 𝑃𝑆 = 𝑎/4 + 3c/4
The profits of the firms are
𝜋1 = (𝑎 − 𝑐) (𝑎 + 𝑐)/4𝑏 𝜋2 = (𝑎 − 𝑐) (𝑎 + 𝑐)/8𝑏
Equilibrium and profits
BP makes more profits than Shell
There is a first mover advantage
Commitment (Credible? Investment capacity!)
BP makes more profits with Stackelberg than
with Cournot competition
Slides 7
(Chapter 12)
2
Entry
What drives entry in markets?
What are barriers to entry?
Scale economies
One firm is “better”
Network effects
Predation
Limit pricing: Set low price to prevent entry
Predatory pricing: Set low price to force exit
Capacity choice
3
Two-stage game:
Bresnahan and Reiss 1991
Potential entrants choose (simultaneously)
whether to enter or not
Upon entry, they compete in price or quantity
Demand is 𝐷 𝑝 𝑆 where 𝑆 is market size
Entry (or fixed) cost 𝐸
If 𝑁 firms enter, variable profit per custom is 𝑉 𝑁
with 𝜕𝑉 𝑁 /𝜕𝑁 ≤ 0
4
How many firms?
The profit of each firm 𝑖 = 1,2,…,𝑁 is
𝜋𝑖 𝑆,𝑁 = 𝑆𝑉 𝑁 − 𝐸
To sustain 𝑁 firms we need 𝑆 ≥ 𝐸/𝑉 𝑁
If 𝑆 is large we get lot of firms with small 𝑉 𝑁
Big markets have a lot of firms
Lot of restaurants in SF, a few less in SC
But we know many big markets with small 𝑁
NYC
6. pricing: Set low price to force exit
3
Two-stage game:
Bresnahan and Reiss 1991
whether to enter or not
� � � where � is market size
�
� firms enter, variable profit per custom is � �
with �� � /�� ≤ 0
7. 4
How many firms?
� = 1,2,…,� is
�� �,� = �� � − �
� firms we need � ≥ �/� �
� is large we get lot of firms with small � �
�
Example:
Entry with BP/Shell Cournot
Demand is � � = � − ��
� �� = ��� for � = 1,2
Example:
Entry with BP/Shell Cournot
8. �1 = �2 = (� − �)
2/9�
�1 = (� − �)
2/4�
Example:
Entry with BP/Shell Cournot
� = 10, � = 1, and � = 2
�1 = �2 = 7 �
1
9
�1 = 16
� = 10 only BP enters
Example:
Entry with BP/Shell Cournot
� = 6. What can BP do?
9. �1
��������
= �1
� = 4
�2 = 2, � = 4, and �2 = 4
Example:
Entry with BP/Shell Cournot
� < 4, BP needs �1
��������
> 4 to deter entry!
� is too low
Example:
Entry with BP/Shell Cournot
� = 1
10. What �1
��������
is needed to deter entry?
�2 given �1 = �1
��������
�2 = 4 −
1
2
�1
��������
2
≤ 1 if �1
��������
≥ 6
Example:
Entry with BP/Shell Cournot
�1
��������
= 6 and �1 = 12
11. �1 = 8
�1
��������
= 6 and deters entry!
Slides 8
(Chapter 14)
2
What did we learn from static
oligopoly models?
th two
firms competing “non-cooperatively”
both firms to “over produce” (or “under price”)
relative to monopoly behavior
12. 3
Can the firms do better?
“better” equilibrium, compared to the Cournot or
Bertrand Nash equilibria
l show that supporting collusive behavior
requires that the firms compete more than once
4
Collusion and cartels
discipline and reduce competition between a
group of suppliers
14. reason analysis: Is there a legitimate, welfare-
enhancing reason to permit the activity?
7
Collusion and cartels – the law
Justice (DOJ)
ison sentences for executives found guilty
competitor!!!
8
Some cartels are never formed
Putnam, CEO Braniff Air: Do you have a suggestion for me?
Crandall, CEO American Airlines: Yes, I have a suggestion
15. for you. Raise your damn fares 20%. I’ll raise mine the
next morning.
Putnam: Robert, we...
Crandall: You’ll make more money and I will too...
Putnam: We can’t talk about pricing!
Crandall: Oh (expletive deleted), Howard. We can talk
about any damn thing we want to talk about.
Conversation taped by DOJ, 2/21/82
9
Collusion and cartels
-legally binding threats or self-
interest
17. eaters? (enforcement of the
collusive agreement)
12
An example before we dive into
theory: the lysine cartel
-1990s, several international firms
conspired to fix worldwide lysine prices
Largest conspirator was Archer Daniels Midland
(ADM). Huge grain and seed company.
executive (Mark Whitacre) who was involved in a
different case
cartel meetings
18. 13
Now a major
motion picture!
14
An example before we dive into
theory: the lysine cartel
convicted on separate
embezzlement charges
15
FBI Recordings of the lysine cartel
in to their meeting, and about their biggest
19. customer (Tyson Foods) sitting in.
—one of the Japanese
firms doesn’t want to meet in Hawaii because it’s
in the U.S.
“trade association”
16
FBI Recordings of the lysine cartel
—to the penny
per pound—for the US and Canada
cheaters. It will use its excess capacity
-of-year
compensation scheme
buy from another firm
20. Slides 9
(Chapter 14)
2
Bertrand competition
� � = 10 − �
� �� = 2�� for � = 1,2
-shot game
�∗ = 2 and �∗ = 0 for both of them!
�� = 6 and �∗ = 8
---incentives to deviate
3
Do repeated interactions help?
21. �� in period 1
�� in period 2 if both played �� in 1
�� in period 2 is not credible. It is just a one-shot
Bertrand, so �2 = �
∗ = 2
So period 1 NE is also Bertrand
4
Continues…
iods?
-shot Bertrand! Then, last but
one is also Bertrand! ….
22. 5
Infinitely repeated game
is probability α the game will
continue to the next period!
– α the game will end
ount rare is δ = α / (1 + r)
Continues…
��� per-period
23. �� = �
�=0
���
��
�1� = �2� = �
∗
Continues…
� = ��
� = �� if �1� = �2� = �
� for all s < t
� = 2 otherwise (punish if deviates!)
rm can be
better off by deviating
Continues…
26. 1. Differentiated Bertrand competition versus price leadership.
The demand for two brands of
laundry detergent, Wave (W) and Rah (R), are given by the
following demands:
Qw = 80 – 2pW + pR QR = 80 – 2pR + pW
The firms have identical cost functions, with a constant
marginal cost of 10.
The firms compete in prices.
(a) What is the best response function for each firm? (that is,
what is firm W's optimal price
as a function of firm R’s price, and vice-versa?) What is the
equilibrium to the one-shot
pricing game? What are the profits of each firm?
(b) Suppose the manufacturer of Wave could commit to setting
pw before the manufacturer of
Rah could set pR. How would this change the equilibrium?
What are the profits of each
firm in this case? Should Wave take advantage of this
commitment possibility? Why or
why not?
(c) Is there a first or second-mover advantage in this game?
First-mover advantage is like the
27. conventional Stackelberg quantity-leadership story, while
second-mover advantage is
reversed. Explain the intuition for your answer, and compare /
contrast with the Stackelberg
quantity-setting story.
2. Entry deterrence via quantity pre-commitment. The U.S.
market for hand sanitizer is controlled
by a monopoly (firm I, for incumbent) that has a total cost given
by TC(qI) = 0.025
2
I
q and
MC(qI) = 0.05qI. The market demand for hand sanitizer is given
by P = 50 – 0.1Q. Under
monopoly, Q = QI.
(a) What is the monopolist’s optimal price and output?
(b) Now let there be a foreign firm (firm E, for entrant) that is
considering entry into the
market. Because the entrant must ship hand sanitizer all the way
across the ocean, its costs
are higher. Specifically, the entrant’s costs are given by TC(qE)
= 10qE + 0.025
2
28. E
q and
MC(qE) = 10 + 0.05qE. Suppose that the incumbent monopolist
has committed to the
monopoly output level. What is the residual demand faced by
the entrant? How much
output will the entrant export to the U.S.? What will be the U.S.
price of hand sanitizer?
(c) Show that the monopolist would need to commit to produce
400 units in order to deter
entry of the foreign firm. (Hint: figure out the monopolist’s
output level q* such that the
entrant loses money if it exports anything other than zero.)
What are the incumbent’s profits
if it commits to this output level and deters entry?
(d) If the incumbent decides to accommodate entry, what
quantity will it commit to?
(e) Will the incumbent deter or accommodate entry in this
market?
3. Collusion and punishment. Suppose the market demand for
lumber is given by:
29. There are two symmetric producers in the market, each with a
constant marginal cost of 10.
(a) What are the monopoly price, quantity, and profits in this
market?
(b) What are the Cournot price, quantities, and profits in this
market?
(c) Suppose the two firms compete in the following infinitely
repeated game:
(i) Each firm produces qi = q
*
(ii) If any firm produces q>q*, then each firm believes that both
will revert to the one-
shot Cournot quantity qc, forever.
What is the critical value of the firms’ discount factor δ such
that q* = 0.5Qm (where Qm is
the monopoly output) is the equilibrium outcome to this game?
(d) Suppose the firms instead set price, given the cost functions
above and no capacity
constraints. What is the equilibrium price and quantity to this
one-shot stage game?
(e) Let the firms in part (d) compete repeatedly in the
following infinitely repeated Bertrand
game:
30. (i) Each firm sets pi = p
*
(ii) If any firm produces p<p*, then each firm believes that both
will revert to the one-
shot Bertrand price pB, forever.
What is the critical value of the firms’ discount factor δ such
that p* = pm is the equilibrium
outcome to this game? Which type of competition, price or
quantities, is more likely to
sustain the monopoly outcome? Why?
4. Factors affecting the sustainability of collusion. Consider an
infinitely repeated Bertrand trigger
pricing game (for example, question 3(e) above). Describe how
each of the following
conditions would affect the sustainability of a collusive
outcome, if at all.
(a) The government’s Competition Commission announces
plans to publish a monthly list of
all transactions prices and volumes in this market, in an effort
to improve “market
transparency” for consumers.
31. (b) Recent regulations require users of the product to convert to
less environmentally-
hazardous substitutes over the next five years. At that point,
production and sales of this
product will be banned.