Econ 357 ASSIGNMENT 4
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ASSIGNMENT 4 (Econ 357)
Problem 1:
There are N (identical) minivan manufacturers in France. Denote by yi the production of the manufacturer i = 1, .., N. The cost function of each minivan manufacturer is C(yi ) = 10yi . The inverse demand for the minivans is p(y) = 1000 − y where y is the aggregate supply. Assume that only manufacturers located in France supply the minivans for the local market and all production decisions are made simultaneously.
1. First, find the aggregate level of production and price in two extreme
cases: in the case of monopoly, and in the case of perfect competition.
Solution:
2. Plot the inverse demand function and mark the two points located on it - one for monopoly and one for perfect competition.
Solution:
3. Find analytically the level of aggregate production and prices for N = 2 (duopoly). Mark the corresponding value on the graph from 2.
Solution:
There are two firms denoted by 1,2. The profit of firm 1 is
π 1 = (1000 − y1 − y2 )y1 − 10y1 .
The first derivative of π 1 with respect to y1 should be set to 0:
1000 − 2y1 − y2 = 10
so that the best response of firm 1 for any quantity y2 is
990 − y2
2 .
Since the problem is symmetric, the best response function of firm 2 is
990 − y1
2 .
You can plug in the best response of firm 1 into the best response of firm 2 (we are doing this because Nash equilibrium requires that each firm best responds to the best response of the other firm!) which yields the equilibrium quantity
y2(←) = 990
Using y2(←) in the best response function for firm 1 results in
y 1(←) = 990
Thus, the aggregate quantity produced by both firms is 2 , and the corresponding price is
p(y) = 1000 − 990.
4. Find analytically the level of aggregate production and prices for N = 5.
Assume that the equilibrium is symmetric which means that in equilibrium
all firms produce the same amount of output. Mark the corresponding
values on the graph from 2.
Solution:
The profit function of firm 1 is:
5
π 1 = (1000 − y1 − yi )y1 − 10y1 .
i=2
The first order condition for firm 1 yields
y1 = 990 − i=2 yi
and the best response function is similar for firms 2,..,5. Notice that we
are focusing on symmetric equilibrium, which is mentioned in the task.
Thus, in equilibrium y1 = .. = y5 . Thus, we can rewrite the best response
function of, say, firm 1 as
990 − 4y1
2
and this yields
y 1(←) = 990
Thus, the aggregate quantity is 990, and the market price is 1000 − 990.
5. Describe the differences in market outcomes in 3. and 4. What do you
think happens if N increases further and goes to infinity?
Solution:
With higher number of firms the price goes down due to competitive pres-
sure, and the aggregate output increases. With other words, both price
and quantity converge to the case of perfect competition since due to a
larger number of firms and a competitive pressure, the firms’ market power
decreases. As the number of firms goes to infinity, the market structure
converges to perfect competition where the market power of each firm is
negligibly small.
Problem 2:
Now, think about the same market (and the same cost structure) as in task
1, and assume N = 2 (duopoly). However, assume for this task that the firms
choose prices and not quantities. The price decisions are made simultaneously.
Since the minivans are identical, the consumers choose the cheapest minivan. If both firms choose same prices, the consumers are indifferent which minivan to buy. In this case each consumer randomizes and buys a minivan from one of the firms with probability .
Show carefully that it is a Nash equilibrium for both firms to choose p = MC .
←*五á : Remember that a strategy profile is a Nash equilibrium if no player has an incentive to unilaterally deviate from the given strategy profile. With other words, if the other player plays her part of the Nash equilibrium, the player would not like to do something different than what is prescribed by the
equilibrium.
Solution:
Here is the equilibrium description provided by Varian:
2022-04-26