perfect comp characteristics
atomistic - large number of buyers and seller
homogenous product
perfect knowledge
no collaboration
free to leave and enter a market
oligopoly characteristics
oligopoly topology
Cournot Model:
OUTPUT
- Each firm picks a level of output based on assumption other firm output is fixed
e.g. airlines decide number of flights then charge based on WTP
Bertrand Model:
PRICES
- Firms pick price level that maxes profits assuming other firms prices are fixed
Cournot Model Assumptions
Zero Conjectural Variation Assumption (ZCVA)
Expected change output in Firm when firm A changes output
QeB/QA = 0, QeA/QB= 0
Isoprofits
Reaction functions
Shows level of output that would max profits for firm
- Further to the right of RFa, firm B produces less
-> therefore firm a can obtain more market share
Cournot-Nash Equilibrium
C-N Monopoly
If one firm does not produce anything => the other is a monopoly
M - evenly shared monopoly output
Output at M < C-N
Profit at M > C-N
Output at PC > C-N
Profit at PC < C-N
Weaknesses of Cournot-Nash
Each firm takes output as given (ZCVA) which is unrealistic:
-> Under ZCVA, firms dont realise their actions have effect on competitor
=> limits firm to only aim for C-N
-> In reality could tacitly collude/cooperate and aim for M where both make higher π
Still allows to identify outcome of no cooperation or after cooperation breaks down
Forms of collusion
Cartels:
Examples of Cartels
Bridgestone Tyres
- Manipulated the prices of antivibration rubber parts (£255M) US DOJ
Libor price thinking
China fined 12 japanese car part manufacturers for price fixing 1.2 bn yuan
- Under China’s anti-trust law, which was enacted in 2008, authorities can fine a company as much as 10% of its annual revenues.
Libor Scandal
In 2012, some banks falsely reported their rates that they periodically report in the interbank market.
rig key rate of London interbank lending rate
Tacit Collusion
Firm influence market outcomes without formal agreements or commitments between firms
Conjecture approach
Based on conjecture that firms make about reaction of other firms
Dropping ZCVA
Size of conjecture => degree of the effectiveness of collusion
Game Theory
Study how independent agents make decisions under uncertainty
Different types:
- Single period vs multi period
- Simultaneous vs sequential
- Constant sum or nonconstant sum
- Zero sum game
Prisoner dilemma
What is the dominant strategy of each firm
-> best strategy no matter what competitor does
-> whichever returns highest profit
C-N = High/High
M = Low/Low
M in prisoner dilemma
By dropping assumptions can reach M
Tit For Tat assumptions
period t:
A Produce low
Period t+1:
B produce low = πCoop
B produce high = πCheat
period t+2:
A retaliate to high = πcheat
leads to πcheat from then on
or leads to πcoop onliy
Coop Condition
PV Coop > PV Cheating
πCoop +πCoop/r > πCheat + πC-N/r
PV Coop(Low)
πCoop + πCoop/r
PV Cheat(High)
πCheat + πC-N/r
Isolating R
r - discount rate
r < (πCoop-πC-N)/(πCheat-πCoop)
πCoop-πC-N - reward for cooperation, the greater this is the more likely to coop
πCheat-πCoop - reward for cheating. the smaller the more likely coop is