1. Flashcards
What do we assume about knock on effects to other markets?
The can be ignored, partial equilibrium analysis
What does d=0 mean?
The goods are independent
What does d>0 mean?
The goods are substitutes
What does d<0 mean?
The goods are complements
What is a way of thinking about consumer surplus?
The extra income needed to compensate consumers for not being able to buy goods
Assumptions of perfect competition
-homogeneous goods
-attempt to max profits
-firms are price takers
-free entry and exit (at least in the LR)
In perfect competition what is average revenue equal to?
Marginal revenue and price
What does the shape of the LR market supply depend on in perfect competition?
How the expansion/ contraction of the industry affects the firms’ cost curves
What is a constant cost market?
-change in market supply has no effect on costs
-LR market supply curve is horizontal
What is an increasing cost market?
-increase in market supply leads to increase in costs
-LR market supply curve upward sloping
What is a decreasing cost market?
-increase in market supply leads to decrease in costs
-LR market supply curve is downward sloping
Is the LR equilibrium for perfect competition efficient?
-P=MC (allocative efficiency)
-firms produce at min(AC) (productive efficiency)
Assumptions of monopoly
-firm serves whole market
-barriers to entry
-firms make economic profit in LR
How do you mathematically find the profit maximising quantity a monopoly chooses?
Differentiate the profit function wrt q and set equal to zero to get the FOC. Solve to find q*. Check SOC condition is less than zero to prove it is a maximising point
What determines the size of the price- marginal cost mark up in a monopoly?
The elasticity of demand. The less elastic demand is, the higher the mark up
What is the Lerner Index?
The difference between price and marginal cost as a % of the price. It is 1/ elasticity of demand
How would a multi plant monopoly pick a quantity that maximises profit?
Set MR=MC1=MC2
Equalise MC across the plants
Two part tariff
Where there is a purchase of a base product and also complementary services for an extra fee
How should a monopolist set price to maximise profit in a two part tariff?
Set price to maximise SW then set access fee to extract all SW as profit
Why might a two part tariff not be equivalent to perfect discrimination in reality?
In practice, consumers may be heterogeneous and it isn’t possible to charge different prices to different consumers
Oligopoly
Few producers of a good who set their own price
Nash equilibrium
A set of strategies, one for each player, such that each player is maximising its payoff given the other player’s strategies
When should a cournot model be used?
When firms simultaneously choose quantities to set
When will a corner equilibrium occur in a cournot duopoly?
When firm 2’s MC is greater than firm 1’s monopoly price
When is stackelberg used?
When firms compete over quantity but one firm moves first
Subgame perfect nash equilibrium
Requires each player’s strategy maximises their payoff given the strategy of others in every subgame
What does SPNE rule out which NE doesn’t?
Unreasonable equilibria that relies on incredible threats
How does a first mover’s payoff in the stackelberg model compare to when firms move simultaneously
First mover always gets the same or better payoff as it does in a simultaneous game
How does the payoff of being a follower in a stackelberg game compare to a simultaneous game?
May be better or worse depending on structure
What is a natural moving order?
Where one firm prefers moving first snd the other prefers moving second
How do subsidies in international trade benefit the domestic firm?
In essence, the gov’s prior action in setting a subsidy changes the domestic firm’s set of credible actions in the output rivalry
What happens in the Brander and Spencer model if both governments decide to use subsidies?
They settle on the same equilibrium subsidy
How could both countries benefit more in the Brander and Spencer model?
If they agreed to set a negative subsidy (ie an export tax) then domestic welfare would be maximised
When is the Bertrand model used?
When firms choose prices simultaneously
What is the equilibrium outcome in a Bertrand model with constant per unit costs?
All firms produce at P=AC
When is there likely to be many equilibria in a Bertrand model?
When costs per unit are increasing and identical firms charge a common price
What is an important feature of Bertrand models?
They are demand determined, so once a firm commits to a price it must serve as many units as customers demand at that price
What do we assume about consumers in the Bertrand model with uninformed consumers?
Informed consumers know prices on offer and buy from cheapest firm as long as it is less than their reservation price.
Uninformed consumers choose firm as random as long as price is less than their reservation price
Why doesn’t an equilibrium unravel to P=MC=AC in the Bertrand model with uninformed consumers?
Because p=MC=AC is a strictly dominated strategy. You can guarantee a positive profit from charging the reservation price
What is a property of a mixed strategy?
Any price used in equilibrium must yield the same expected payoff otherwise a firm would increase its payoff by using the more profitable prices more frequently
When will the Bertrand paradox not hold?
When consumers are uninformed
When there is product differentiation
When per unit cost rises with quantity
How do prices compare when modelling efficiency, collusion, quantity competition and price competition in a model with product differentiation?
Order of price lowest to highest
1. Efficiency
2. Price competition
3. Quantity competition
4. Collusion