Transcript Intermediate Microeconomics

Intermediate Microeconomics
Monopoly
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Pure Monopoly
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A Monopolized market has only a single seller.
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Examples:
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XM radio?
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Microsoft?
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Walmart in a small town?
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Monopolies
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So what causes monopolies?
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Legal Constraints:
 e.g patents for new drugs
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Ownership of a fixed resource
 e.g. toll highway, land in a given area.
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Collusion
 e.g. several producers act as one (OPEC)
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Large economies of scale (natural monopolies)
 e.g. land line phone service, utilities, Google? Microsoft?
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Monopolies
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Why are we concerned about Monopolies?
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Implications of Monopoly
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Key to Monopoly: Seller is not a price taker!
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Specifically, since monopolist chooses market supply, it essentially
picks a point on the market demand curve to operate on.
This means that for a monopolist, equilibrium price is a function of the
quantity they supply, so they effectively get to choose both
 i.e. choose where to operate on p(q) (“Inverse Demand Curve”)
$
QD(p) or p(q)
Q
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Monopolist’s Problem
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In perfect competition, a firm wanted to choose a quantity to maximize
profits, given it is a “price taker”.
max π(q) = R(q) – C(q)
= pq – C(q)
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To find profit maximizing q, we take derivative of π(q) and set it equal to zero,
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This gives
p - MC(q*) = 0
“First Order Condition” (FOC)
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or equivalently, keep producing until MC(q*) = p
Like any firm, a monopolist wants to choose quantity to maximize profits,
but by doing so effectively chooses price as well.
max π(q) = R(q) – C(q)
= p(q)q – C(q)
So what will be profit maximization condition for the monopolist?
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Monopolist’s Problem
$
c(Q)
R(Q) = p(Q)Q
q
π(Q)
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Marginal Revenue for Monopolist
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Profit max condition is always MR(q*) = MC(q*) (from FOC)
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For firm in perfect competition, firm is a price taker so MR(q) = p for all q.
For monopolist: MR(q*) = [p’(q*)q* + p(q*)]
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Since p(q) is the inverse of the market demand curve, we know p’(q) < 0.
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Therefore, [p’(q)q + p(q)] < p(q), implying MR(q) < p(q) (i.e. marginal
revenue from producing and selling another unit is less than price)
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What is intuition?
Ex: Consider a Market Demand Curve: QD(p) = 400 – 5p
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What is Equation for the Inverse Demand curve?
What is Equation for Marginal Revenue curve?
Graphically?
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Monopolist Behavior
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Consider a monopolist:
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Cost function given by C(q) = q2 + 8q + 20
Market Demand Curve of QD(p) = 400 – 5p.
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What will be equilibrium price and quantity?
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Graphically?
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Profit Maximization and Demand Elasticity
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Recall that R(q) = p(q)q
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So MR(q) = p’(q) q + p(q)
= p(q)[p’(q) q/p(q) + 1]
Recall ε(p) = Q’(p) p/Q(p)
= slope of demand curve times price divided by quantity
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So 1/ε = slope of inverse demand curve times quantity divided by price
= p’(q) q/p(q)
So MR(q) = p(q)[1/ε + 1]
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Recalling ε < 0, what does this tell us about output under a monopoly
and demand elasticity, recognizing that Monopolist will choose q to
equate MR(q) to MC(q)?
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Profit Maximization and Demand Elasticity
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We can actually learn even more from elasticity.
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In competitive markets, firms produced until
p = MC(q*)
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Alternatively, monopolist supplies until MR(q*) = MC(q*), or until:
p(q*)[1/ε + 1] = MC(q*)
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Re-writing we get:
p(q*) = MC(q*)ε /[ε +1]
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So how does monopoly “mark-up” depend on elasticity of demand?
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Monopoly and Efficiency
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The key implication of a Pareto Efficient
outcome is that all possible gains from trade are
exhausted.
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Will this be true in a monopolized market?
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Consider first what it means for all gains from
trade to be exhausted.
 Output is produced as long as marginal cost of
last unit is less than what a consumer is
willing to pay for that unit.
How do we know this won’t be true under a profit
maximizing monopolist? How would we see this
graphically?
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Monopoly and Efficiency
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What would happen if a monopolist could
charge different prices to different consumers?
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How much would it supply? What would happen
regarding efficiency?
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Is this possible?
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Monopoly and Efficiency
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Price Discrimination – charging different prices to
different consumers.
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Examples?
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For a firm to effectively price discriminate:
 Groups must have different demand elasticities.
 It must be possible to determine which group a
given customer belongs to at a low cost.
 It must be difficult for consumer to resell the good
in question.
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Can increase efficiency, but what happens to
consumer surplus?
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Taxing a Monopolist
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What if government imposes a tax on monopolist equal to $t/unit
sold. Will this somehow increase efficiency?
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Consider again monopolist with Cost function given by C(q) = q2 + 8q
+ 20 and Market Demand Curve of QD(p) = 400 – 5p (inverse market
demand curve of p(Q) = 80 – Q/5)
So (from before) we know MC(q) = 2Q + 8 and MR(Q) = 80 – 2Q/5
 Therefore, without tax, Q = 30 and p = 74
 What will change with tax of t = $12?
Graphically?
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Entry
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If a monopolist is making all these economic profits, can this
monopoly be maintained?
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Entry constrained by law (patents, patronage/political favors)
Natural Monopoly - firm’s technology has economies-of-scale large
enough for it to supply the whole market at a lower average cost than is
possible with more than one firm in the market.
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Essentially very high fixed costs of entry.
 Examples?
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Monopoly Policy
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Under natural monopoly it is best for one firm to supply whole
market.
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To prevent inefficiencies of monopoly, there are a couple of strategies.
 Have government run/regulate industry.
 e.g. Utilities, postal service?
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Break-up monopolist
 Especially relevant when declining marginal cost structure due to
high entry costs (e.g. software, drugs)
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Block mergers that could allow monopolies to form in the first place.
 Problems?
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