1. Game Theory: Inside Oligopoly

2. Introduction
Behavior of competitors, or impact of own actions, cannot be ignored in oligopoly
Managers maximize profit or market share by outguessing competitors
Insight into oligopolistic markets by using GAME THEORY (Von Neumann and Morgenstern in 1950): designed to evaluate situations with conflicting objectives or bargaining processes between at least two parties.

3. Types of Games Normal Form vs. Extensive Form
Simultaneous vs. Sequential (act without knowing (one player moves other player’s strategy) after observing others)
One Shot vs. Repeated (infinite and finite with uncertain and certain final period)
Zero Sum vs. Non-zero Sum (market share) (profit maximization)

4. A Normal Form Game Elements of the game: Players
Strategies or feasible actions Payoff matrix
Planed decision or actions
Player 2
12,11
11,12
14,13
Player 1
11,10
10,11
12,12
10,15
10,13
13,14
Results from strategy dependent on the strategies of all the players

5. Dominant Strategy
Regardless of whether Player 2 chooses A, B, or C, Player 1 is better off choosing “a”! (Indiana Jones and the Holy Grail)
“a” is Player 1’s Dominant Strategy!
Player 2
2’s best strategy c
c a
12,11
11,12
14,13
Player 1
11,10
10,11
12,12
10,15
10,13
13,14
1’s best a a a strategy

6. The Outcome What should player 2 do?
2 has no dominant strategy, but should reason that 1 will play “a”.
Therefore 2 should choose “C”.
Player 2
12,11
11,12
14,13*
14,13
Player 1
11,10
10,11
12,12
10,15
10,13
13,14
This outcome is called a Nash equilibrium (set of strategies were no player can improve payoffs by unilaterally changing own strategy given other player’s strategy)
“a” 1’s best response to “C” and “C” is 2’s best response to “a”.

7. Best Response Strategy
Try to predict the likely action of competitor to identify your best response:
Conjecture choice of rival
Select your own best response
Was conjecture reasonable or
Look for dominant strategies
Put yourself in your rival’s shoes

8. Market-Share Game Equilibrium
• Two managers want to maximize market share (zero-sum game) • Strategies are pricing decisions • Simultaneous moves • One-shot game
Manager 2
Manager 1
Nash Equilibrium

9. Dominated Strategy Dominance exception rather than rule
In absence of dominance it might be possible to simplify the game by eliminating dominated strategy (never played: lowest payoff regardless of other player’s strategy)
Steelers trial by 2, have the ball & enough time for 2 plays
Payoff matrix in yards gained by offense: no dominant strategy
Pass dominant offense without Blitz (dominated defense)
Defense
Best Defense Run
Pass 2 6 14
Offense 8 7* 10
Best Offense Pass Pass Run

10. Maximin or Secure Strategy
In absence of dominant strategy risk averse players may abandon Nash or best response (*) and seek maximin option (^) that maximizes the minimum possible payoff.
This is not design to maximize payoff but rather to avoid highly unfavorable outcomes (choose the best of all worst).
Firm 1
Firm 2
Best for 1 New 6 None 3 Min for 2 None 3 New 2
Best Min for for 1 New New 3 None None 2
Board of Getty Oil agreed to sell 40% stake to $128.5 in Jan Board of Getty Oil subsequently accepted Texaco’s offer for $128. Pennzoil sued Texaco for breach of contract & received $10 bill jury award in Texaco appealed. Before Supreme Court’s decision, they settled for $3 bill in

11. Examples of Coordination Games
Industry standards
size of floppy disks
size of CDs
etc.
National standards
electric current
traffic laws

12. A Coordination Problem: Three Nash Equilibria!
Player 2
Player 1

13. Key Insights:
In some cases one-shot, non-cooperative games result in undesirable outcome for individuals (prisoner’s dilemma) and some times for society (advertisement).
Communication can help solve coordination problems.
Sequential moves can help solve coordination problems.
Time in jail, Nash (*) and Maximin (^) equilibrium in Prisoner’s dilemma.
Suspect 2
Best Max for for 1 Confess Confess Do Not Confess
Suspect 1
Best for 1 Confess Do Not Max for 2 Confess Confess

14. One-Shot Advertising Game Equilibrium
• Kellogg’s & General Mills want to maximize profits • Strategies consist of advertising campaigns • Simultaneous moves • One-shot interaction • Repeated interaction
General Mills
Kellogg’s
Nash Equilibrium

15. Repeating the game 2 times will not improve outcome
In the last period the game is a one-shot game, so equilibrium entails High Advertising.
Period 1 is “really” the last period, since everyone knows what will happen in period 2.
Equilibrium entails High Advertising by each firm in both periods.
The same holds true if we repeat the game any known, finite number of times.
General Mills *
Kellogg’s
Nash Equilibrium

16. Can collusion work if firms play the game each year, forever?
Consider the “trigger strategy” by each firm:
“Don’t advertise, provided the rival has not advertised in the past. If the rival ever advertises, “punish” it by engaging in a high level of advertising forever after.”
Each firm agrees to “cooperate” so long as the rival hasn’t “cheated”, which triggers punishment in all future periods.
“Tit-for-tat strategy” of copying opponents move from the previous period dominates “trigger strategy” for:
Simple to understand
Never invites nor rewards cheating
Forgiving: allows cheater to restore cooperation by reversing actions

17. Suppose General Mills adopts this trigger strategy. Kellogg’s profits?
Cooperate = /(1+i) + 12/(1+i)2 + 12/(1+i)3 + …
= /i
Value of a perpetuity of $12 paid
at the end of every year
Cheat = 20 +2/(1+i) + 2/(1+i)2 + 2/(1+i)3 + …
= /i
General Mills
Kellogg’s

18. Kellogg’s Gain to Cheating:
Cheat - Cooperate = /i - ( /i) = /i
Suppose i = .05
Cheat - Cooperate = /.05 = = -192
It doesn’t pay to deviate.
Collusion is a Nash equilibrium in the infinitely repeated game!
General Mills
Kellogg’s

19. Benefits & Costs of Cheating
Cheat - Cooperate = /i
8 = Immediate Benefit ( today)
10/i = PV of Future Cost ( forever after)
If Immediate Benefit > PV of Future Cost
Pays to “cheat”.
If Immediate Benefit  PV of Future Cost
Doesn’t pay to “cheat”.
General Mills
Kellogg’s

20. Key Insight
Collusion can be sustained as a Nash equilibrium when game lasts infinitely many periods or finitely many periods with uncertain “end”.
Doing so requires:
Ability to monitor actions of rivals
Ability (and reputation for) punishing defectors
Low interest rate
High probability of future interaction

21. Real World Examples of Collusion: Garbage Collection Industry
Homogeneous products Known identity of customers Bertrand oligopoly Known identity of competitors
Firm 2
One-Shot Bertrand (Nash) Equilibrium
Firm 1
Firm 2
Repeated Game Equilibrium
Firm 1

22. Real World Examples of Collusion: OPEC
Cartel founded in 1960 by Iran, Iraq, Kuwait, Saudis and Venezuela: “to co-ordinate and unify petroleum policies among Members in order to secure fair and stable prices”
Absent collusion: PCompetition < PCournot (OPEC) < PMonopoly
Venezuela
One-Shot Cournot (Nash) Equilibrium
Saudi Arabia
Venezuela
Repeated Game Equilibrium Assuming a Low Interest Rate
Saudi Arabia

23. OPEC’s Demise
Low Interest
Rates
High Interest
Rates

24. Simultaneous-Move Bargaining
Management and a union are negotiating a wage increase.
Strategies are wage offers & wage demands.
Simultaneous, one-shot move at making a deal.
Successful negotiations lead to $600 million in surplus (to be split among the parties), failure results in a $100 million loss to the firm and a $3 million loss to the union.
Experiments suggests that, in the absence of any “history,” real players typically coordinate on the “fair outcome”
When there is a “bargaining history,” other outcomes may prevail
Union
Three Nash Equilibriums in Normal Form
Management

25. Single Offer Bargaining
Now suppose the game is sequential in nature, and management gets to make the union a “take-it-or-leave-it” offer.
Analysis Tool: Write the game in extensive form
Summarize the players
Their potential actions
Their information at each decision point
The sequence of moves and
Each player’s payoff

26. To get The Game in Extensive Form
Step 1: Management’s Move Step 2: Add the Union’s Move Step 3: Add the Payoffs
Firm 10 5 1
Union
Accept
Reject
100, 500
-100, -3
300, 300
500, 100

27. Step 4: Identify Nash Equilibriums
Outcomes such that neither player has an incentive to change its strategy, given the strategy of the other
Firm 10 5 1
Union
Accept
Reject
100, 500
-100, -3
300, 300
500, 100

28. Step 5: Find the Subgame Perfect Nash Equilibriums
Outcomes where no player has an incentive to change its strategy, given the strategy of the rival, that are based on “credible actions”: not the result of “empty threats” (not in its “best self interest”).
Firm 10 5 1
Union
Accept
Reject
100, 500
-100, -3
300, 300
500, 100

29. Re-Cap
In take-it-or-leave-it bargaining, there is a first-mover advantage.
Management can gain by making a take-it or leave-it offer to the union. But...
Management should be careful, however; real world evidence suggests that people sometimes reject offers on the the basis of “principle” instead of cash considerations.

30. Pricing to Prevent Entry: An Application of Game Theory
Two firms: an incumbent and potential entrant.
Identify Nash and then Subgame Perfect Equilibria.
Entrant
Out
Enter
Incumbent
Hard
Soft
-1, 1
5, 5
0, 10 *
Establishing a reputation for being unkind to entrants can enhance long-term profits. It is costly to do so in the short-term, so much so that it isn’t optimal to do so in a one-shot game.

31. The Value of a Bad Reputation: Price Retaliation
In early 1970s General Foods’ Maxwell House dominated the non-instant coffee market in the Eastern USA, while Proctor & Gamble’s Folgers dominate Western USA.
In 1971 P&G started advertising & distributing Folgers in Cleveland and Pittsburgh.
GF’s immediately increased advertisement & lowered prices (sometimes below cost) in these regions & midwestern cities (Kansas City) where both marketed.
GF’s profit dropped from 30% in 1970 to –30% in When P&G reduced its promotional activities, GF’s price increased and profits were restored.

32. Limit Pricing
Strategy where an incumbent prices below the monopoly price in order to keep potential entrants out of the market.
Goal is to lessen competition by eliminating potential competitors’ incentives to enter the market.
Incumbent produces QL instead of monopoly output QM.
Resulting price, PL, is lower than monopoly price PM.
Residual demand curve is the market demand DM minus QL.
Entry is not profitable because entrant’s residual demand lies below AC
Optimal limit pricing results in a residual demand such that, if the entrant entered and produced Q units, its profits would be zero.
Quantity $ Q M P AC
Entrant's residual
demand curve D
P = AC L
(DM – QL)