Chapter Twenty-Three
Industry Supply
行业供给
Structure
Market supply
Short-run supply and equilibrium
Long-run supply and equilibrium
Long-run implications for taxation
Fixed inputs and economic rent (经济租金 )
Supply From A Competitive Industry
How are the supply decisions of the
many individual firms in a
competitive industry to be combined
to discover the market supply curve
for the entire industry?
Supply From A Competitive Industry
Since every firm in the industry is a
price-taker,total quantity supplied at
a given price is the sum of quantities
supplied at that price by the
individual firms.
Short-Run Supply
In a short-run the number of firms in
the industry is,temporarily,fixed.
Let n be the number of firms;
i = 1,…,n.
Si(p) is firm i’s supply function.
Short-Run Supply
In a short-run the number of firms in
the industry is,temporarily,fixed.
Let n be the number of firms;
i = 1,…,n.
Si(p) is firm i’s supply function.
The industry’s short-run supply
function isS p S pi
i
n
( ) ( ),
1
Supply From A Competitive Industry
p
S1(p)
p
S2(p)
Firm 1’s Supply Firm 2’s Supply
Supply From A Competitive Industry
p
S1(p)
p
S2(p)p
p’
p’
S1(p’)
S1(p’)
Firm 1’s Supply Firm 2’s Supply
S(p) = S1(p) + S2(p)
Industry’s Supply
Supply From A Competitive Industry
p
S1(p)
p
S2(p)p
S(p) = S1(p) + S2(p)
p”
p”
S1(p”)
S1(p”)+S2(p”)
S2(p”)
Firm 1’s Supply Firm 2’s Supply
Industry’s Supply
Supply From A Competitive Industry
p
S1(p)
p
S2(p)p
Firm 1’s Supply Firm 2’s Supply
S(p) = S1(p) + S2(p)
Industry’s Supply
Short-Run Industry Equilibrium
In a short-run,neither entry nor exit
can occur.
Consequently,in a short-run
equilibrium,some firms may earn
positive economics profits,others
may suffer economic losses,and still
others may earn zero economic
profit.
Short-Run Industry Equilibrium
Market demand
Short-run industry
supply
pse
Yse Y
Short-run equilibrium price clears the
market and is taken as given by each firm.
Short-Run Industry Equilibrium
y1 y2 y3
ACs
ACs AC
s
MCs
MCs
MCs
y1* y2* y3*
pse
Firm 1 Firm 2 Firm 3
Short-Run Industry Equilibrium
y1 y2 y3
ACs
ACs AC
s
MCs
MCs
MCs
y1* y2* y3*
pse
Firm 1 Firm 2 Firm 3
P1 > 0 P2 < 0 P3 = 0
Short-Run Industry Equilibrium
y1 y2 y3
ACs
ACs AC
s
MCs
MCs
MCs
y1* y2* y3*
pse
Firm 1 Firm 2 Firm 3
Firm 1 wishes
to remain in
the industry.
Firm 2 wishes
to exit from
the industry.
Firm 3 is
indifferent.
P1 > 0 P2 < 0 P3 = 0
Long-Run Industry Supply
In the long-run every firm now in the
industry is free to exit and firms now
outside the industry are free to enter.
The industry’s long-run supply
function must account for entry and
exit as well as for the supply choices
of firms that choose to be in the
industry.
How is this done?
Long-Run Industry Supply
Positive economic profit induces
entry.
Economic profit is positive when the
market price pse is higher than a
firm’s minimum av,total cost;
pse > min AC(y).
Entry increases industry supply,
causing pse to fall.
When does entry cease?
Long-Run Industry Supply
S2(p)
Mkt,Demand
AC(y)MC(y)
y
A,Typical” FirmThe Market
p p
Y
Suppose the industry initially contains
only two firms.
Mkt.
Supply
Long-Run Industry Supply
S2(p)
Mkt,Demand
AC(y)MC(y)
y
A,Typical” FirmThe Market
p p
Y
p2 p2
Then the market-clearing price is p2.
Long-Run Industry Supply
S2(p)
Mkt,Demand
AC(y)MC(y)
y
A,Typical” FirmThe Market
p p
Y
p2 p2
y2*
Then the market-clearing price is p2.
Each firm produces y2* units of output.
Long-Run Industry Supply
S2(p)
Mkt,Demand
AC(y)MC(y)
y
A,Typical” FirmThe Market
p p
Y
p2 p2
y2*
P > 0
Each firm makes a positive economic
profit,inducing entry by another firm.
Long-Run Industry Supply
S2(p)
S3(p)
Mkt,Demand
AC(y)MC(y)
y
A,Typical” FirmThe Market
p p
Y
p2 p2
Market supply shifts outwards.
y2*
Long-Run Industry Supply
S2(p)
S3(p)
Mkt,Demand
AC(y)MC(y)
y
A,Typical” FirmThe Market
p p
Y
p2 p2
Market supply shifts outwards.
Market price falls.
y2*
Long-Run Industry Supply
S2(p)
S3(p)
Mkt,Demand
AC(y)MC(y)
y
A,Typical” FirmThe Market
p p
Y
p3
Each firm produces less.
y3*
p3
Long-Run Industry Supply
S2(p)
S3(p)
Mkt,Demand
AC(y)MC(y)
y
A,Typical” FirmThe Market
p p
Y
p3
Each firm produces less.
Each firm’s economic profit is reduced.
y3*
p3 P > 0
Long-Run Industry Supply
S3(p)
Mkt,Demand
AC(y)MC(y)
y
A,Typical” FirmThe Market
p p
Y
p3
Each firm’s economic profit is positive.
Will another firm enter?
y3*
p3 P > 0
Long-Run Industry Supply
S4(p)
S3(p)
Mkt,Demand
AC(y)MC(y)
y
A,Typical” FirmThe Market
p p
Y
p3
Market supply would shift outwards again.
y3*
p3
Long-Run Industry Supply
S4(p)
S3(p)
Mkt,Demand
AC(y)MC(y)
y
A,Typical” FirmThe Market
p p
Y
p3
Market supply would shift outwards again.
Market price would fall again.
y3*
p3
Long-Run Industry Supply
S4(p)
S3(p)
Mkt,Demand
AC(y)MC(y)
y
A,Typical” FirmThe Market
p p
Y
p4
Each firm would produce less again.
y4*
p4
Long-Run Industry Supply
S4(p)
S3(p)
Mkt,Demand
AC(y)MC(y)
y
A,Typical” FirmThe Market
p p
Y
p4
Each firm would produce less again,Each
firm’s economic profit would be negative.
y4*
P < 0
p4
Long-Run Industry Supply
S4(p)
S3(p)
Mkt,Demand
AC(y)MC(y)
y
A,Typical” FirmThe Market
p p
Y
p4
Each firm would produce less again,Each
firm’s economic profit would be negative.
So the fourth firm would not enter.
y4*
P < 0
p4
Long-Run Industry Supply
The long-run number of firms in the
industry is the largest number for
which the market price is at least as
large as min AC(y).
Now we can construct the industry’s
long-run supply curve,
Long-Run Industry Supply
Suppose that market demand is large
enough to sustain only two firms in
the industry.
Long-Run Industry Supply
S2(p)
S3(p)
Mkt,Demand
AC(y)MC(y)
y
A,Typical” FirmThe Market
p p
Y
p2’
y2*
p2’
Long-Run Industry Supply
Suppose that market demand is large
enough to sustain only two firms in
the industry.
Then market demand increases,the
market price rises,each firm
produces more,and earns a higher
economic profit.
Long-Run Industry Supply
S2(p)
S3(p)
Mkt,Demand
AC(y)MC(y)
y
A,Typical” FirmThe Market
p p
Y
p2’
y2*
p2’
Long-Run Industry Supply
S2(p)
S3(p)
Mkt,Demand
AC(y)MC(y)
y
A,Typical” FirmThe Market
p p
Y
p2”
y2*
p2”
Long-Run Industry Supply
S2(p)
S3(p)
Mkt,Demand
AC(y)MC(y)
y
A,Typical” FirmThe Market
p p
Y y2*
p2” p2”
Long-Run Industry Supply
S2(p)
S3(p)
Mkt,Demand
AC(y)MC(y)
y
A,Typical” FirmThe Market
p p
Y y2*
Notice that a 3rd firm will not enter since it
would earn negative economic profits.
p2” p2”
Long-Run Industry Supply
As market demand increases further,
the market price rises further,the
two incumbent firms each produce
more and earn still higher economic
profits -- until a 3rd firm becomes
indifferent between entering and
staying out.
Long-Run Industry Supply
S2(p)
S3(p)
Mkt,Demand
AC(y)MC(y)
y
A,Typical” FirmThe Market
p p
Y y2*
p2” p2”
Long-Run Industry Supply
S2(p)
S3(p)
Mkt,Demand
AC(y)MC(y)
y
A,Typical” FirmThe Market
p p
Y y2*
p2’” p2’”
Long-Run Industry Supply
S2(p)
S3(p)
Mkt,Demand
AC(y)MC(y)
y
A,Typical” FirmThe Market
p p
Y y2*
A third firm can now enter,causing all firms
to earn zero economic profits.
p2’” p2’”
Long-Run Industry Supply
So any further increase in market
demand will cause the number of
firms in the industry to rise to three.
Long-Run Industry Supply
S2(p)
S3(p)
Mkt,Demand
AC(y)MC(y)
y
A,Typical” FirmThe Market
p p
Y y2*
The only relevant part of the short-run
supply curve for n = 2 firms in the industry.
p2’” p2’”
Long-Run Industry Supply
How much further can market
demand increase before a fourth firm
enters the industry?
Long-Run Industry Supply
Mkt,Demand
AC(y)MC(y)
y
A,Typical” FirmThe Market
p p
Y
p3’
y3*
S3(p)
S4(p)
p3’
Long-Run Industry Supply
Mkt,Demand
AC(y)MC(y)
y
A,Typical” FirmThe Market
p p
Y
p3’
y3*
A 4th firm would now earn negative
economic profits if it entered the industry.
p3’
S3(p)
S4(p)
Long-Run Industry Supply
S3(p)
Mkt,Demand
AC(y)MC(y)
y
A,Typical” FirmThe Market
p p
Y y3*
S4(p)
But now a 4th firm would earn zero
economic profit if it entered the industry.
p3’ p3’
Long-Run Industry Supply
S3(p)
Mkt,Demand
AC(y)MC(y)
y
A,Typical” FirmThe Market
p p
Y y3*
S4(p)p
3’ p3’
The only relevant part of the short-run
supply curve for n = 3 firms in the industry.
Long-Run Industry Supply
Continuing in this manner builds the
industry’s long-run supply curve,
one section at-a-time from
successive short-run industry supply
curves,
Long-Run Industry Supply
AC(y)MC(y)
y
A,Typical” FirmThe Market
Long-Run
Supply Curve
p p
Y y3*
Long-Run Industry Supply
AC(y)MC(y)
y
A,Typical” FirmThe Market
Long-Run
Supply Curve
p p
Y y3*
Notice that the bottom of each segment of
the supply curve is min AC(y).
Long-Run Industry Supply
As each firm gets,smaller” relative to
the industry,the long-run industry
supply curve approaches a horizontal
line at the height of min AC(y).
Long-Run Industry Supply
AC(y)MC(y)
y
A,Typical” FirmThe Market
Long-Run
Supply Curve
p p
Y y3*
Notice that the bottom of each segment of
the supply curve is min AC(y).
Long-Run Industry Supply
AC(y)
MC(y)
y
A,Typical” FirmThe Market
Long-Run
Supply Curve
p p
Y y*
The bottom of each segment of the supply
curve is min AC(y),As firms get,smaller”
the segments get shorter.
Long-Run Industry Supply
AC(y)
MC(y)
y
A,Typical” FirmThe Market
Long-Run
Supply Curve
p p
Y y*
In the limit,as firms become infinitesimally
small,the industry’s long-run supply
curve is horizontal at min AC(y).
Long-Run Market Equilibrium Price
In the long-run market equilibrium,
the market price is determined solely
by the long-run minimum average
production cost.
Long-run market price is
p AC ye
y
m in ( ).
0
Implications
Economic profit=0
All factors are priced at market
values,or opp,costs.
Like a firm with constant returns to
scale in the long run.
Long-Run Implications for Taxation
In a short-run equilibrium,the burden
of a sales or an excise tax is typically
shared by both buyers and sellers,
tax incidence of the tax depending
upon the own-price elasticities of
demand and supply.
Q,Is this true in a long-run market
equilibrium?
Tax Incidence in the Short-Run
p
D(p),S(p)
Market
demand
Market
supply
p*
q*
pb
qt
ps
Tax paid by
buyers
Tax paid by
sellers
Tax incidence =
p p
p p
b
s
*
*
.
Long-Run Implications for Taxation
LR supply (no tax)
p
X,Y
Mkt,demand
Qe
pe
Long-Run Implications for Taxation
LR supply (no tax)
p
X,Y
Mkt,demand
Qe
ps=pe
LR supply (with tax)
Qt
pb =
pe+t
t
Long-Run Implications for Taxation
LR supply (no tax)
p
X,Y
Mkt,demand
Qe
ps=pe
LR supply (with tax)
Qt
pb =
pe+t
t
In the long-run the
buyers pay all of a
sales or an excise tax.
Fixed Inputs and Economic Rent
What if there is a barriers to entry or
exit?
E.g.,the taxi-cab industry has a
barrier to entry even though there are
lots of cabs competing with each
other,
Liquor licensing is a barrier to entry
into a competitive industry.
Sources of Barriers to Entry
Nature
–Land
–Oil field
–Entrepreneurial skills
–Talent
Regulation
–License
–Land use regulations
Fixed Inputs and Economic Rent
Q,When there is a barrier to entry,
will not the firms already in the
industry make positive economic
profits?
Fixed Inputs and Economic Rent
Q,When there is a barrier to entry,
will not the firms already in the
industry make positive economic
profits?
A,No,Each firm in the industry
makes a zero economic profit,Why?
Fixed Inputs and Economic Rent
An input (e.g,an operating license)
that is fixed in the long-run causes a
long-run fixed cost,F.
Long-run total cost,c(y) = F + cv(y).
And long-run average total cost,
AC(y) = AFC(y) + AVC(y).
In the long-run equilibrium,what will
be the value of F?
Fixed Inputs and Economic Rent
Think of a firm that needs an operating
license -- the license is a fixed input
that is rented but not owned by the firm.
If the firm makes a positive economic
profit then another firm can offer the
license owner a higher price for it,In
this way,all firms’ economic profits are
competed away,to zero,
Fixed Inputs and Economic Rent
So in the long-run equilibrium,each
firm makes a zero economic profit
and each firm’s fixed cost is its
payment for its operating license,
Fixed Inputs and Economic Rent
y
$/output unit
AC(y)
AVC(y)MC(y)
y*
pe
The firm’s economic
profit is zero.
Fixed Inputs and Economic Rent
y
$/output unit
AC(y)
AVC(y)MC(y)
y*
pe
F The firm’s economic
profit is zero.
F is the payment to the owner of the fixed
input (the license).
Fixed Inputs and Economic Rent
Economic rent is the payment for an
input that is in excess of the
minimum payment required to have
that input supplied.
Each license essentially costs zero
to supply,so the long-run economic
rent paid to the license owner is the
firm’s long-run fixed cost.
Fixed Inputs and Economic Rent
y
$/output unit
AC(y)
AVC(y)MC(y)
y*
pe
F The firm’s economic
profit is zero.
F is the payment to the owner of the fixed
input (the license); F = economic rent.
Beneficiaries of Entry Barriers
Owners of the fixed factor
–Taxi-license owners
When market price for product
increases
–Accounting profit rises
–Labor costs unchanged because
labor market is competitive
–Rent increases.
Keep a rent
–Lobby against eliminating barriers
Create rent
–Fees for inter-provincial migration
–Study-abroad agency
Rent-Seeking Behavior (寻租行为 )
When the Government Creates Rent
Tradable right to entry
– Open market trade
E.g.,auction
– Under the table trade
Corruption
Non-tradable rights
– 租金耗散
Lawyer
Stamps
Land Rent
Why negative rent?
–Taxes and fees
Idling the land
Migration