What will you learn in this chapter?
• Characteristics of a competitive market.
• How to construct a demand curve.
• Shift in vs. a movement along the demand curve.
• How to construct a supply curve.
• Shift in supply vs. movement along supply curve.
• How demand and supply interact to bring markets to equilibrium.
• How changes in supply and demand influence equilibrium price and quantity
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1© 2014 by McGraw‐Hill Education 1
Chapter 3
Markets
© 2014 by McGraw‐Hill Education 2
What will you learn in this chapter?
• Characteristics of a competitive market.
• How to construct a demand curve.
• Shift in vs. a movement along the demand curve.
• How to construct a supply curve.
• Shift in supply vs. movement along supply curve.
• How demand and supply interact to bring markets
to equilibrium.
• How changes in supply and demand influence
equilibrium price and quantity.
© 2014 by McGraw‐Hill Education 3
Markets
• A market refers to the buyers and sellers who trade a
particular good or service.
– Markets can be located locally, globally, or even virtually.
• One special class of markets is the competitive market.
• Four characteristics of perfectly competitive markets.
• In this chapter, markets are assumed to be perfectly
competitive.
Standardized good No transaction costs
Full information Participants are price takers
2© 2014 by McGraw‐Hill Education 4
Demand
• As a group, consumers determine the demand
for a product.
• The quantity demanded is the amount of a
particular good or service that buyers are
willing and able to purchase at a given price.
• The law of demand states that the lower the
price, the higher the quantity demanded, all
other things equal.
© 2014 by McGraw‐Hill Education 5
Cell phones
(millions)
Price
($)
30
90
120
150
180
210
240
270
60
180
140
160
120
100
80
60
40
20
The demand schedule
• A demand schedule
displays the quantities
demanded at various
prices.
• This demand schedule
provides the quantity of
cellphones demanded at
specific prices.
• Notice that as price falls,
the quantity demanded
increases.
© 2014 by McGraw‐Hill Education 6
Cell phones
(millions)
Price
($)
30
90
120
150
180
210
240
270
60
180
140
160
120
100
80
60
40
20
The demand curve
Quantity of cell phones (millions)
30 60 90 120 150 180 210 240 270
1. As the price decreases
0
20
40
60
80
100
120
140
160
180
200
220
Price ($)
2. the quantity demand
increases.
The demand curve illustrates the relationship between the quantity demanded and the
price of the good, holding all of the other non‐price determinants constant.
3© 2014 by McGraw‐Hill Education 7
Active Learning: Constructing demand
Use the following demand schedule to construct the demand curve.
0
1
2
3
4
5
6
7
8
140 160 180 200 220 240 260 280 300
P
Q
Price Quantity
1 280
2 260
3 240
4 220
5 200
6 180
7 160
8 140
© 2014 by McGraw‐Hill Education 8
Changes in demand
• The five most important non‐price
determinants of demand are:
• What happens when one of the non‐price
determinants changes?
– If positive influence, demand increases.
– If negative influence, demand decreases.
Preferences Number of buyers
Incomes Expectations
Price of related goods
© 2014 by McGraw‐Hill Education 9
• When demand
increases, the
demand curve shifts
to the right.
• When demand
decreases, the
demand curve shifts
to the left.
Shifting the demand curve
0
40
80
120
160
200
240
0 60 120 180 240
Quantity of cell phones (millions)
Price ($)
DA
DB
DC
4© 2014 by McGraw‐Hill Education 10
Shifts versus movements
There is an important difference between a shift in the demand
curve and a movement along the demand curve.
If the price decreases, then quantity
demanded increases and there is a
movement along the demand curve.
If a non‐price determinant changes,
then the demand curve shifts with
changes in the quantity demanded
at every price.
Quantity of cell phones (millions)
0
40
80
120
160
200
240
60 120 180 240
Price ($)
DB
DA
DC
D
Quantity of cell phones (millions)
0
40
80
120
160
200
240
60 120 180 240
Price ($)
© 2014 by McGraw‐Hill Education 11
Active Learning: Shifts vs. movements
Indicate whether a shift or movement occurs in
the market for cellphones when each of the
following determinants changes.
– Advertising causes individuals to prefer cellphones
over home phones.
– Cellphones go on sale.
– Cellphone calling plans become more expensive.
© 2014 by McGraw‐Hill Education 12
Supply
• As a group, producers determine the supply of
a product.
• The quantity supplied is the amount of a
particular good that producers are willing and
able to purchase at a given price.
• The law of supply states that the higher the
price, the higher the quantity supplied, all
other things equal.
5© 2014 by McGraw‐Hill Education 13
Cell phones
(millions)
Price
($)
270
210
180
150
120
90
60
30
240
180
140
160
120
100
80
60
40
20
The supply schedule
• A supply schedule
displays the
quantities supplied at
various prices.
• This supply schedule
provides the quantity
of cellphones
supplied at specific
prices.
• Notice that as price
increases, the
quantity supplied
increases.
© 2014 by McGraw‐Hill Education 14
Cell phones
(millions)
Price
($)
270
210
180
150
120
90
60
30
240
180
140
160
120
100
80
60
40
20
The supply curve
2. quantity supplied increases
0
20
40
60
80
100
120
140
160
180
200
30 60 90 120 150 180 210 240 270
Price ($)
Quantity of cell
phones (millions)
1. As price increases
© 2014 by McGraw‐Hill Education 15
Active Learning: Constructing supply
Use the following supply schedule to construct the supply curve.
0
1
2
3
4
5
6
7
8
140 160 180 200 220 240 260 280 300
P
Q
Price Quantity
1 130
2 260
3 390
4 520
5 650
6 780
7 910
8 1040
6© 2014 by McGraw‐Hill Education 16
Changes in supply
• The five most important non‐price
determinants of supply are:
• What happens when one of the non‐price
determinants changes?
– If positive influence, supply increases.
– If negative influence, supply decreases.
Technology Number of producers
Price of Inputs Expectations
Price of related goods
© 2014 by McGraw‐Hill Education 17
• When supply
increases, the supply
curve shifts to the
right.
• When supply
decreases, the supply
curve shifts to the
left.
Shifting the supply curve
0
40
80
120
160
200
240
0 60 120 180 240 300
Quantity of cell phones (millions)
Price ($)
SA
SC
SB
© 2014 by McGraw‐Hill Education 18
Shifts versus movements
There is an important difference between a shift in the supply
curve and a movement along the supply curve.
If a non‐price determinant changes,
then the supply curve shifts with
changes in the quantity supplied at
every price.
If the price decreases, then quantity
supplied decreases and there is a
movement along the supply curve.
Quantity of cell phones (millions)
0
40
80
120
160
200
240
60 120 180 300240
Price ($)
S C
S A
S B
Quantity of cell phones (millions)
0
40
80
120
160
200
240
60 120 180 300240
Price ($)
SA
7© 2014 by McGraw‐Hill Education 19
Active Learning: Shifts vs. movements
• Indicate whether a shift or movement occurs
in the market for cellphones when each of the
following determinants change.
– A new Chinese cellphone manufacturer enters the
market.
– Producers expect cellphones prices to rise.
– The price of calling over the Internet (e.g. Skype)
decreases.
© 2014 by McGraw‐Hill Education 20
Market equilibrium
• The equilibrium is where
the supply curve
intersects the demand
curve.
– At this point, consumers
are willing to buy exactly
what producers are
willing to sell.
• The equilibrium price is
$100.
• The equilibrium quantity
is 150 M.Quantity of cell phones (millions)
0
200
50 100 150 300200 250
Price ($)
S
D
50
100
150
© 2014 by McGraw‐Hill Education 21
Active Learning: Finding equilibrium
1) Graph the supply and demand curve and find the equilibrium.
2) Circle the market equilibrium price and quantity in the schedule.
0
1
2
3
4
5
6
7
8
140 160 180 200 220 240 260 280 300 Q
P
Price QS QD
1 130 280
2 260 260
3 390 240
4 520 220
5 650 200
6 780 180
7 910 160
8 1040 140
8© 2014 by McGraw‐Hill Education 22
Disequilibrium
• What happens when the market is not in
equilibrium?
• If the market price is not equal to the equilibrium
price, then quantity demanded is not equal to
quantity supplied.
– If the price is too high, excess supply occurs and there
is a surplus of the good or service.
• A lower price alleviates the surplus.
– If the price is too low, excess demand occurs and there
is a shortage of the good or service.
• A higher price alleviates the shortage.
© 2014 by McGraw‐Hill Education 23
A surplus
• A surplus provides incentives for
the price to decrease.
• As the price decreases
1) The quantity supplied
decreases.
2) The quantity
demanded increases.
• The price continues to decrease
until QS = QD = Q*.
QD QS
40
80
160
120
200
300
Price ($)
Quantity of cell phones (millions)
0 60 120 180 240
S
D
Surplus
(excess supply)
Price is
too high
© 2014 by McGraw‐Hill Education 24
A shortage
• A shortage provides incentives for
the price to increase.
• As the price increases
1) The quantity supplied
increases.
2) The quantity demanded
decreases.
• The price continues to increase
until QS = QD = Q*.
S
D
Quantity of cell phones (millions)
0
40
80
160
120
200
60 120 180 300240
Price ($)
Shortage
(excess demand)
Price is
too low
QS QD
9© 2014 by McGraw‐Hill Education 25
Active Learning: Excess supply
1) Find the quantity demanded and quantity supplied at a price of $3.
2) Quantify the excess supply (surplus).
P QS QD
1 130 280
2 260 260
3 390 240
4 520 220
5 650 200
6 780 180
7 910 160
8 1040 140
© 2014 by McGraw‐Hill Education 26
Active Learning: Excess demand
1) Find the quantity demanded and quantity supplied at a price of $1.
2) Quantify the excess demand (shortage).
P QS QD
1 130 280
2 260 260
3 390 240
4 520 220
5 650 200
6 780 180
7 910 160
8 1040 140
© 2014 by McGraw‐Hill Education 27
Changes in market equilibrium
• The equilibrium price and quantity are determined by the
intersection of the demand and supply curves.
• If a non‐price factor changes, this affects the market
equilibrium.
• To determine the effect on market equilibrium, there are
three questions that must be answered:
– Does the change affect demand? If so, how?
– Does the change affect supply? If so, how?
– What happens to equilibrium price and quantity?
10
© 2014 by McGraw‐Hill Education 28
Shifts in demand
Suppose the price of land‐line service suddenly
skyrockets.
D2
0
20
40
60
80
100
120
140
160
180
200
0 30 60 90 120 150 180 210 240 270 300
Quantity of cell phones (millions)
Price ($)
D1
S2
• Market for cellphones is in
equilibrium.
• More expensive substitute
causes the demand to
increase.
• The demand curve shifts right.
• The market equilibrium
changes.
– Equilibrium price increases.
– Equilibrium quantity increases.
© 2014 by McGraw‐Hill Education 29
Active Learning: Equilibrium effects from
shifts in demand
P QS QD Q’D
8 270 30
7 240 60
6 210 90
5 180 120
4 150 150
3 120 180
2 90 210
1 60 240
Suppose the demand curve shifts outward by 60 units. Update
the demand schedule and find the new equilibrium price and
quantity.
© 2014 by McGraw‐Hill Education 30
S2
Shifts in supply
• Market for cellphones is
initially in equilibrium.
• Increased technology causes
the supply to increase.
• The supply curve shifts right.
• The market equilibrium
changes.
– Equilibrium price decreases.
– Equilibrium quantity
increases.
Suppose there is a breakthrough in battery technology.
0
20
40
60
80
100
120
140
160
180
200
0 30 60 90 120 150 180 210 240 270 300
Quantity of cell phones (millions)
Price ($)
D1
S1
11
© 2014 by McGraw‐Hill Education 31
Active Learning: Equilibrium effects from
shifts in supply
D
S
P
Q
P*
Q*
Ice Cream Market
Suppose the cost of sugar, an input for making ice cream,
increases. Identify whether supply, demand, or both shift(s)
and the new equilibrium price and quantity for ice cream.
© 2014 by McGraw‐Hill Education 32
Shifts in demand or supply
When either demand or supply changes, there is
an unambiguous effect on equilibrium price and
quantity.
Curve Change Price change Quantity change
Supply Decrease
Supply Increase
Demand Decrease
Demand Increase
© 2014 by McGraw‐Hill Education 33
Shifts in both demand and supply
• It is possible for non‐price factors that influence both
demand and supply at the same time.
• This leads to shifts in both demand and supply.
• The new equilibrium occurs at the new intersection.
• Suppose that landline phone service prices increase
and an input price to make cellphones decreases.
– Demand increases.
– Supply increases.
• What happens to equilibrium price and quantity?
– It depends on whether the demand or supply curve shifts
out more.
12
© 2014 by McGraw‐Hill Education 34
Shifts in both demand and supply
New equilibrium
– Quantity increases.
– Price increases.
Conclusion: Quantity increases.
Price may increase or decrease (ambiguous).
New equilibrium
– Quantity increases.
– Price decreases.
Quantity of cell phones (millions)
0
60
40
20
100
80
120
140
200
180
160
30 60 90 120 150 300180 210 240 270
Price ($)
(A) Demand increases more
S 1
D 2
S 2
E1
E2
D 1
(B) Supply increases more
Quantity of cell phones (millions)
0
60
40
20
100
80
120
140
200
180
160
30 60 90 120 150 180 210 240 270
Price ($)
S 1
S 2
E
E
D
D 2
1
2
1
© 2014 by McGraw‐Hill Education 35
Shifts in demand and supply
When both supply and demand shift and the
magnitudes of change are unknown, the effect
on either price or quantity is known, but not
both.
Supply change Demand change Price change Quantity change
Decrease Decrease
Decrease Increase
Increase Increase
Increase Decrease
© 2014 by McGraw‐Hill Education 36
Summary
• A market is the group of buyers and sellers
who trade.
– A competitive market exists if a large number of
buyers and sellers trade standardized goods and
services.
–Modeled using supply and demand.
13
© 2014 by McGraw‐Hill Education 37
Summary
• Demand demonstrates consumers’ highest
willingness to pay for a given quantity.
• The law of demand states that the quantity
demanded increases as the price decreases.
– The demand curve has a negative slope.
• When one of the non‐price determinants of
demand changes, the entire demand curve
shifts to the left or the right.
© 2014 by McGraw‐Hill Education 38
Summary
• Supply demonstrates producers’ lowest price
that they must receive to sell a given quantity.
• The law of supply states that the quantity
supplied increases as the price increases.
– The supply curve has a positive slope.
• When one of the non‐price determinants of
supply changes, the entire supply curve shifts
to the left or the right.
© 2014 by McGraw‐Hill Education 39
Summary
• The equilibrium price and quantity are identified
when quantity supplied equals quantity
demanded. At this point:
– Producers sell all they desire at the equilibrium price.
– Consumers buy all they desire at the equilibrium price.
• If the market price is not equal to the equilibrium
price, then a surplus or shortage exists, and the
price adjusts until quantity demanded is equal to
quantity supplied.
14
© 2014 by McGraw‐Hill Education 40
Summary
• When a non‐price determinant changes, the
effect on equilibrium price and quantity can be
evaluated by:
– Determining whether supply, demand, or both are
affected.
– Determining the direction supply, demand, or both
shift(s).
– Comparing the new equilibrium to the initial
equilibrium to identify the effect on price and
quantity.