Post on 01-Apr-2015
Market Power: Monopoly and
Monopsony
Chapter 9
1
Review of Perfect Competition
• P = LMC = LRAC• Normal profits or zero economic profits in
the long run• Large number of buyers and sellers• Homogenous product• Perfect information• Firm is a price taker
2
Review of Perfect Competition
Q
P MarketD S
Q0
P0
Q
P Individual Firm
P0D = MR = P
q0
LRACLMC
3
Monopoly
• Monopoly1. One seller - many buyers2. One product (no good substitutes)3. Barriers to entry4. Price Maker
• The monopolist is the supply-side of the market and has complete control over the amount offered for sale.
• Monopolist controls price but must consider consumer demand
• Profits will be maximized at the level of output where marginal revenue equals marginal cost.
4
Average & Marginal Revenue
• The monopolist’s average revenue, price received per unit sold, is the market demand curve.
• Monopolist also needs to find marginal revenue, change in revenue resulting from a unit change in output.
• Finding Marginal Revenue– As the sole producer, the monopolist works with
the market demand to determine output and price.
– An example can be used to show the relationship between average and marginal revenue
– Assume a monopolist with demand:P = 6 - Q
5
Average and Marginal Revenue
Average Revenue (Demand)
MarginalRevenue
0
1
2
3
$ perunit ofoutput
4
5
6
7
Output1 2 3 4 5 6 7
6
We can also see algebraically that Q* maximizes profit. Profit π is the difference between revenue and cost, both of which depend on Q:
As Q is increased from zero, profit will increase until it reaches a maximum and then begin to decrease. Thus the profit-maximizing Q is such that the incremental profit resulting from a small increase in Q is just zero (i.e., Δπ /ΔQ = 0). Then
But ΔR/ΔQ is marginal revenue and ΔC/ΔQ is marginal cost. Thus the profit-maximizing condition is that
, or
7
Monopolist’s Output Decision
P*
Q*
P2
Q2
MC
AC
Lostprofit
Lostprofit
D = AR
MR
P1
Q1
$ perunit ofoutput
Quantity
8
Monopoly: An Example
CMC
QQCCost
2
50)( 2
RMR
QQQQPQR
QQPDemand
240
40)()(
40)(:2
9
Monopoly: An Example
10
404
2402
Q
Q
MRMC
30)(
1040)(
40)(
QP
QP
QQP
10
A Rule of Thumb for Pricing
Note that the extra revenue from an incremental unit of quantity, Δ(PQ)/ΔQ, has two components:
1. Producing one extra unit and selling it at price P brings in revenue (1)(P) = P.
2. But because the firm faces a downward-sloping demand curve, producing and selling this extra unit also results in a small drop in price ΔP/ΔQ, which reduces the revenue from all units sold (i.e., a change in revenue Q[ΔP/ΔQ]).
Thus,
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Now, because the firm’s objective is to maximize profit, we can set marginal revenue equal to marginal cost:
which can be rearranged to give us
Equivalently, we can rearrange this equation to express price directly as a markup over marginal cost:
(Q/P)(ΔP/ΔQ) is the reciprocal of the elasticity of demand, 1/Ed, measured at the profit-maximizing output, and
12
Example of Profit Maximization
$/Q
10
20
40
0 5 10 15 20
P=30
Profit
MC
AC
AR
MR
Quantity
Profit = (P - AC) x Q = ($30 - $15)
(10) = $150
AC=15
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A Rule of Thumb for Pricing
Q
PQ
Q
RMR
)(
.1
• Produce one more unit brings in revenue (1)(P) = P
• With downward sloping demand, producing and selling one more unit results in small drop in price P/Q.– Reduces revenue from all units sold,
change in revenue: Q(P/Q)
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A Rule of Thumb for Pricing
PQ
QPE
Q
P
P
QPP
Q
PQPMR
Thus
d.3
.2
15
A Rule of Thumb for Pricing
d
d
EPPMR
EQP
PQ
1.5
1.4
16
A Rule of Thumb for Pricing
D
D
D
E
MCP
EP
MCP
MCE PP
11
1
1
MC MR wheremaximized is
17
A Rule of Thumb for Pricing
12$75.
9
411
9
94
119
.
P
MCE
Assume
E
MCP
d
d
18
Monopoly
• Monopoly pricing compared to perfect competition pricing:– Monopoly
• P > MC• Price is larger than MC by an amount that
depends inversely on the elasticity of demand
– Perfect Competition• P = MC• Demand is perfectly elastic so P=MC
19
Shifts in Demand
• In perfect competition, the market supply curve is determined by marginal cost.
• For a monopoly, output is determined by marginal cost and the shape of the demand curve.
– There is no supply curve for monopolistic market
• Shifts in demand do not trace out price and quantity changes corresponding to a supply curve
• Shifts in demand lead to– Changes in price with no change in output– Changes in output with no change in price– Changes in both price and quantity
20
Monopoly
• Shifts in demand usually cause a change in both price and quantity.
• Example show how monopolistic market differs from perfectly competitive market
• Competitive market supplies specific quantity a every price– This relationship does not exist for a
monopolistic market
21
The Effect of a Tax
• In competitive market, a per-unit tax causes price to rise by less than tax: burden shared by producers and consumers
• Under monopoly, price can sometimes rise by more than the amount of the tax.
• To determine the impact of a tax:– t = specific tax– MC = MC + t
22
Effect of Excise Tax on Monopolist
Q1
P1
D = AR
MR
MC + tax
tMC
Q0
P0
P
$/Q
Quantity
Increase in P: P0 to P1 > tax
23
The Multi-plant Firm• For some firms, production takes place in more
than one plant each with different costs• Firm must determine how to distribute production
between both plants1. Production should be split so that the MC in the
plants is the same2. Output is chosen where MR=MC. Profits is
therefore maximized when MR=MC at each plant• We can show this algebraically:
– Q1 and C1 is output and cost of production for Plant 1
– Q2 and C2 is output and cost of production for Plant 2
– QT = Q1 + Q2 is total output
– Profit is then: = PQT – C1(Q1) – C2(Q2) 24
The Multi-plant Firm
• Firm should increase output from each plant until the additional profit from last unit produced at Plant 1 equals 0
1
1
1
1
11
0
0)(
MCMR
MCMR
Q
C
Q
PQ
QT
25
Deadweight Loss from Monopoly Power
QC
PC
B
CC
A
MC
Lost Consumer Surplus
Deadweight Loss
QmQuantity
$/Q
Because of the higher price,
consumers lose A+B and
producer gains A-C.
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Monopsony
• A monopsony is a market in which there is a single buyer.
• An oligopsony is a market with only a few buyers.• Monopsony power is the ability of the buyer to affect
the price of the good and pay less than the price that would exist in a competitive market.
• Typically choose to buy until the benefit from last unit equals that unit’s cost
• Marginal value is the additional benefit derived from purchasing one more unit of a good– Demand curve – downward sloping
• Marginal expenditure is the additional cost of buying one more unit of a good– Depends on buying power
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Monopsony
• Competitive Buyer– Price taker– P = Marginal expenditure = Average
expenditure– D = Marginal value
• Graphically can compare competitive buyer to competitive seller
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Monopsonist Buyer
D = MV
ME
S = AE
PC
QCQ*m
P*m
$/Q
Quantity
Monopsony•ME above S
•Quantity where ME = MV: Qm
•Price from Supply curve: Pm
Competitive•P = PC
•Q = Q+C
29
Monopoly and Monopsony
• Monopsony is easier to understand if we compare to monopoly
• We can see this graphically• Monopolist
– Can charge price above MC because faces downward sloping demand (average revenue)
– MR < AR– MR=MC gives quantity less than competitive
market and price that is higher
30
Monopoly and Monopsony
$/Q
MV
ME
S = AE
Q*
P*
PC
QC
MonopsonyNote: ME = MV;
ME > AE; MV > P
31
Monopoly and Monopsony
• Monopoly– MR < P– P > MC– Qm < QC– Pm > PC
• Monopsony– ME > P– P < MV– Qm < QC– Pm < PC
32
Monopsony Power
• The degree of monopsony power depends on three factors.
1. Number of buyers• The fewer the number of buyers, the less elastic the
supply and the greater the monopsony power.2. Interaction Among Buyers
• The less the buyers compete, the greater the monopsony power.
3. Elasticity of market supplyExtent to which price is marked down below MV
depends on elasticity of supply facing buyerIf supply is very elastic, markdown will be smallThe more inelastic the supply the more monopsony
power
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