Chapter 17
Demand, Supply, and Equilibrium
Copyright 2002 by The McGrawHill Companies, Inc. All rights reserved.
171
Chapter Objectives
•
•
•
•
•
•
Individual and market demand
Changes in demand
Individual and market supply
Changes in supply
Graphing supply and demand curves
Finding equilibrium price and quantity
Copyright 2002 by The McGrawHill Companies, Inc. All rights reserved.
172
Demand Defined
• Demand is the schedule of quantities of a
good or service that people will purchase
at different prices
– The law of demand: when the price of a good
is lowered, more of it is demanded; When it is
raised, less is demanded
Copyright 2002 by The McGrawHill Companies, Inc. All rights reserved.
173
Individual and Market
Demand
• The law of demand holds for both
individuals and markets
• Individual demand is the schedule of
quantities that a person would purchase
at different prices
• Market demand is the schedule of
quantities that everyone in the market
would buy at different prices
Copyright 2002 by The McGrawHill Companies, Inc. All rights reserved.
174
Table 1 Hypothetical Individual Demand
and Market Demand Schedules
Quantity demanded by Venus
30
Price QD
$30 0
P 24
25 2
r
20 3
15 3
i
10 4
c
5 5
e
18
12
6
0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30
Quantity
175
Copyright 2002 by The McGrawHill Companies, Inc. All rights reserved.
Table 1 Hypothetical Individual Demand
and Market Demand Schedules
Quantity demanded by Martina
30
Price QD
$30 1
P 24
25 1
r
20 2
15 3
i
10 5
c
5 6
e
18
12
6
0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30
Quantity
176
Copyright 2002 by The McGrawHill Companies, Inc. All rights reserved.
Table 1 Hypothetical Individual Demand
and Market Demand Schedules
Quantity demanded by Serena
30
Price QD
$30 2
P 24
25 3
r
20 5
15 6
i
10 7
c
5 7
e
18
12
6
0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30
Quantity
177
Copyright 2002 by The McGrawHill Companies, Inc. All rights reserved.
Table 1 Hypothetical Individual Demand
and Market Demand Schedules
Quantity demanded by Lindsay
30
Price QD
$30 1
P 24
25 3
r
20 4
15 6
i
10 7
c
5 8
e
18
12
6
0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30
Quantity
178
Copyright 2002 by The McGrawHill Companies, Inc. All rights reserved.
Price Venus Martina Serena Lindsay Total
$30 0 1 2 1 4
30
P 24
r
i
c
e
18
12
6
0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30
Quantity
179
Copyright 2002 by The McGrawHill Companies, Inc. All rights reserved.
Price Venus Martina Serena Lindsay Total
$30 0 1 2 1 4
$25 2 1 3 3 9
30
P 24
r
i
c
e
18
12
6
0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30
Quantity
1710
Copyright 2002 by The McGrawHill Companies, Inc. All rights reserved.
Price Venus Martina Serena Lindsay Total
$30 0 1 2 1 4
$25 2 1 3 3 9
$20 3 2 5 4 14
30
P 24
r
i
c
e
18
12
6
0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30
Quantity
1711
Copyright 2002 by The McGrawHill Companies, Inc. All rights reserved.
Price Venus Martina Serena Lindsay Total
$30 0 1 2 1 4
$25 2 1 3 3 9
$20 3 2 5 4 14
$15 3 3 6 6 18
30
P 24
r
i
c
e
18
12
6
0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30
Quantity
1712
Copyright 2002 by The McGrawHill Companies, Inc. All rights reserved.
Price Venus Martina Serena Lindsay Total
$30 0 1 2 1 4
$25 2 1 3 3 9
$20 3 2 5 4 14
$15 3 3 6 6 18
$10 4 5 7 7 23
30
P 24
r
i
c
e
18
12
6
0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30
Quantity
1713
Copyright 2002 by The McGrawHill Companies, Inc. All rights reserved.
Price Venus Martina Serena Lindsay Total
$30 0 1 2 1 4
$25 2 1 3 3 9
$20 3 2 5 4 14
$15 3 3 6 6 18
$10 4 5 7 7 23
$ 5 5 6 7 8 26
30
P 24
r
i
c
e
18
12
6
0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30
Quantity
1714
Copyright 2002 by The McGrawHill Companies, Inc. All rights reserved.
Price Venus Martina Serena Lindsay Total
$30 0 1 2 1 4
$25 2 1 3 3 9
$20 3 2 5 4 14
$15 3 3 6 6 18
$10 4 5 7 7 23
$ 5 5 6 7 8 26
30
Market
Demand
P 24
r
i
c
e
18
12
6
0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30
Quantity
1715
Copyright 2002 by The McGrawHill Companies, Inc. All rights reserved.
What Is the Market?
• The market is where people buy and sell
– Local markets
• Gasoline, groceries
– Regional
• Automobiles
– National or international
• Computers
Copyright 2002 by The McGrawHill Companies, Inc. All rights reserved.
1716
Changes in Demand
A change in demand would be a change in the schedule
Price QD(1) QD(2)
$30 4 5
$25 9 11
$20 14 18
$15 18 28
$10 23 38
$ 5 26 50
30
25
20
15
10
D1
D2
5
0
10
20
30
40
50
Quantity
Copyright 2002 by The McGrawHill Companies, Inc. All rights reserved.
1717
An Increase in Demand
An increase in demand is an increase in the quantity
people are willing to purchase at all prices
Price QD(1) QD(2)
$30 4 5
$25 9 11
$20 14 18
$15 18 28
$10 23 38
$ 5 26 50
30
25
20
15
10
D2
5
The demand
curve shifts to the
right
D1
0
10
20
30
40
50
Quantity
Copyright 2002 by The McGrawHill Companies, Inc. All rights reserved.
1718
An Increase in Demand
A decrease in demand means people are willing to
purchase less at all prices
Price QD(1) QD(2)
$30 4 5
$25 9 11
$20 14 18
$15 18 28
$10 23 38
$ 5 26 50
30
25
20
15
10
D2
5
The demand
curve shifts to the
left
D1
0
10
20
30
40
50
Quantity
Copyright 2002 by The McGrawHill Companies, Inc. All rights reserved.
1719
Changes in Demand
A and B are on the same line, therefore, they are on the same
schedule. If they are on the same schedule, there can be no change
in demand
C
A
B
D1
D2
Move from point A to point B
Copyright
A change in quantity demanded
1720
2002 by The McGrawHill Companies, Inc. All rights reserved.
Changes in Demand
Movement from A to B is simply a change in quantity
demanded in response to a change in price
C
A
B
D1
D2
Move from point A to point B
Copyright
A change in quantity demanded
1721
2002 by The McGrawHill Companies, Inc. All rights reserved.
Changes in Demand
There is an increase in demand because people are willing to
buy more at all prices on G’s curve which is to the right of F’s
curve
E
G
I
F
H
Move from point F to point G
An increase in demand
Copyright 2002 by The McGrawHill Companies, Inc. All rights reserved.
1722
Changes in Demand
There is a decrease in demand because people are willing to
buy less at all prices on H’s curve which is to the left of G’s
curve
E
G
I
F
H
Move from point G to point H
A decrease in demand
Copyright 2002 by The McGrawHill Companies, Inc. All rights reserved.
1723
Changes in Demand
As long as we remain on the same curve, there is no change in
demand
E
G
I
F
H
Move from point H to point I A change in quantity in demanded
1724
Copyright 2002 by The McGrawHill Companies, Inc. All rights reserved.
Changes in Demand
As long as we remain on the same curve, there is no change in
demand
L
J
K
G
M
N
Move from point J to point K A change in quantity in demanded
1725
Copyright 2002 by The McGrawHill Companies, Inc. All rights reserved.