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© 2013 Pearson
Elasticities of Demand
and Supply
5
CHECKPOINTS
© 2013 Pearson
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Checkpoint 5.1
Checkpoint 5.2
Problem 1
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Problem 1
Problem 2
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Problem 2
Problem 2
Problem 3
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In the News
In the News
In the News
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Checkpoint 5.3
Problem 1
CHECKPOINT 5.1
Practice Problem 1
When the price of a good increased by 10 percent,
the quantity demanded of it decreased 2 percent.
Is the demand for this good elastic, unit elastic, or
inelastic?
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CHECKPOINT 5.1
Solution
The demand for a good is inelastic if the percentage
decrease in the quantity demanded is less than the
percentage increase in its price.
In this example, a 10 percent price rise brings a 2
percent decrease in the quantity demanded, so
demand is inelastic.
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CHECKPOINT 5.1
Study Plan Problem
When the price of a good increased by 10
percent, the quantity demanded of it decreased 2
percent.
Demand for this good is __________.
A. Inelastic
B. Elastic
C. unit elastic
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CHECKPOINT 5.1
Practice Problem 2
When the price of a good increased by 10 percent, the
quantity demanded of it decreased 2 percent.
Are substitutes for this good easy to find or does it have
poor substitutes?
Is this good more likely to be a necessity or a luxury?
Why?
Is the good more likely to be narrowly or broadly defined?
Why?
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CHECKPOINT 5.1
Solution
Because the good has an inelastic demand, it most likely
• has poor substitutes.
• is a necessity rather than a luxury.
• is broadly defined.
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CHECKPOINT 5.1
Study Plan Problem
When the price of a good increased by 10 percent,
the quantity demanded of it decreased 2 percent.
Most likely, this good ___________ and
____________.
A.
B.
C.
D.
E.
has poor substitutes; is a luxury
is a necessity; has poor substitutes
is a luxury; is narrowly defined
is a necessity; has good substitutes
is broadly defined; is a luxury
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CHECKPOINT 5.1
Practice Problem 3
When the price of a good increased by 10 percent, the
quantity demanded of it decreased 2 percent.
Calculate the price elasticity of demand for this good.
Explain how the total revenue from the sale of the good
has changed.
Explain which of the following goods this good is most
likely to be: orange juice, bread, toothpaste, theater
tickets, clothing, blue jeans, Super Bowl tickets.
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CHECKPOINT 5.1
Solution
Price elasticity of demand = Percentage change in the
quantity demanded ÷ Percentage change in price.
Price elasticity of demand = 2 ÷ 10 or 0.2.
An elasticity less than 1 means that demand is inelastic.
When demand is inelastic, a price rise increases total
revenue.
This good is most likely a necessity (bread), or has poor
substitutes (toothpaste), or is broadly defined (clothing).
© 2013 Pearson
CHECKPOINT 5.1
Study Plan Problem
When the price of a good increased by 10 percent,
the quantity demanded of it decreased 2 percent.
The price elasticity of demand is ___. A price rise
will ____ total revenue. ____ is a good with such a
demand.
A.
B.
C.
D.
E.
5.0; decrease; Toothpaste
0.2; increase; Toothpaste
0.2; decrease; Super Bowl tickets
5.0; decrease; Blue jeans
5.0; increase; Super Bowl tickets
© 2013 Pearson
CHECKPOINT 5.1
In the News
Music giant chops price to combat downloads
In 2003, when music downloading first took off, Universal
Music slashed the price of a CD from $21 to $15. The
company said that it expected the price cut to boost the
quantity of CDs sold by 30 percent, other things remaining
the same.
Source: Globe and Mail, September 4, 2003
What was Universal Music’s estimate of the price elasticity
of demand for CDs? Was demand estimated to be elastic
or inelastic?
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CHECKPOINT 5.1
Solution
Price elasticity of demand = Percentage change in the
quantity demanded ÷ Percentage change in price.
The Percentage change in the price equals
[($21 – $15)/($18)] × 100, which is 33.3 percent.
The Percentage change in the quantity is 30 percent.
So the estimated price elasticity of demand is
30 percent ÷ 33.3 percent, or 0.9.
An estimated elasticity of 0.9 means that demand is
estimated to be inelastic.
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CHECKPOINT 5.2
Practice Problem 1
You are told that a 10 percent increase in the price of a
good has led to a 1 percent increase in the quantity
supplied of the good after one month and a 25 percent
increase in the quantity supplied after one year.
Is the supply of this good elastic, unit elastic, or inelastic?
Is this good likely to be produced using factors of
production that are easily obtained?
What is the price elasticity of supply of this good?
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CHECKPOINT 5.2
Solution
The supply of a good is inelastic if the percentage
increase in the quantity supplied is less than the
percentage increase in price.
In this example, a 10 percent price rise brings a 1
percent increase in the quantity supplied, so supply is
inelastic.
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CHECKPOINT 5.2
Because the quantity supplied increases by such a small
percentage after one month, the factors of production that
are used to produce this good are more likely to be difficult
to obtain.
The elasticity of supply equals the percentage change in
the quantity supplied divided by the percentage change in
the price.
Elasticity of supply = 1 ÷ 10 or 0.1.
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CHECKPOINT 5.2
Study Plan Problem
You are told that a 10 percent increase in the price
of a good has led to a 1 percent increase in the
quantity supplied of that good after one month.
Supply of the good is ____.
A.
B.
C.
D.
E.
inelastic
unit elastic
elastic
decreasing
increasing
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CHECKPOINT 5.2
Practice Problem 2
You are told that a 10 percent increase in the price of a good
has led to a 1 percent increase in the quantity supplied of
the good after one month and a 25 percent increase in the
quantity supplied after one year.
What is the elasticity of supply of this good after one year?
Has the supply of this good become more elastic or less
elastic? Why?
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CHECKPOINT 5.2
Solution
1.Elasticity of supply = Percentage change in the quantity
supplied ÷ Percentage change in the price.
2.After one year, the elasticity of supply = 25 ÷ 10 = 2.5.
3.The supply of the good has become more elastic over
the year since the price rise.
4.Possibly other producers have gradually started
producing the good and with the passage of time more
factors of production can be reallocated.
© 2013 Pearson
CHECKPOINT 5.2
In the News
Weak coal prices hit China's third-largest coal miner
The chairman of Yanzhou Coal Mining, Wang Xin, reported
that the global financial crisis has decreased the demand for
coal, with its sales falling by 11.9 percent to 7.92 million tons
from 8.99 million tons a year earlier, despite the price falling
by 10.6 percent.
Source: Dow Jones, April 27, 2009
Calculate the price elasticity of supply of coal at Yanzhou
Coal Mining. Is its supply of coal elastic or inelastic?
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CHECKPOINT 5.2
Solution
Elasticity of supply = Percentage change in the quantity
supplied ÷ Percentage change in the price.
Yanzhou Coal Mining’s price elasticity of supply equals
11.9 percent divided by 10.6 percent, or 1.12.
The quantity supplied fell by a larger percentage than the
price, so supply of coal is elastic.
That is what an elasticity of supply of 1.12 means.
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CHECKPOINT 5.3
Practice Problem 1
The quantity demanded of good A increases by 5 percent
when the price of good B rises by 10 percent and other
things remain the same.
Are goods A and B complements or substitutes?
Describe how the demand for good A changes.
Calculate the cross elasticity of demand.
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CHECKPOINT 5.3
Solution
Goods A and B are substitutes
because when the price of good B
rises, the quantity demanded of
good A increases.
As the price of good B rises,
people switch from good B to
good A.
The demand for good A
increases.
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CHECKPOINT 5.3
Cross elasticity of demand = Percentage change in the
quantity demanded of good A ÷ Percentage increase
in the price of good B.
Cross elasticity of demand = 5 ÷ 10 or 0.5.
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CHECKPOINT 5.3
Practice Problem 2
When income rises by 5 percent and other things remain
the same, the quantity demanded of good C increases by
1 percent.
Is good C a normal good or an inferior good?
Describe how the demand for good C changes.
Calculate the income elasticity of demand for good C.
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CHECKPOINT 5.3
Solution
Because the quantity demanded
of good C increases when income
increases, good C is a normal
good.
An increase in income increases
the demand for good C.
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CHECKPOINT 5.3
Income elasticity of demand = Percentage change in
the quantity demanded of good C ÷ Percentage
increase in income.
Income elasticity of demand = 1 ÷ 5 or 0.2.
© 2013 Pearson
CHECKPOINT 5.3
In the News
Rising incomes make China the world’s largest luxury
goods market
China is estimated to become the world’s largest luxury
goods market over the next decade, boosted by rising
incomes and a transition from saving to spending culture.
Source: ibtimes, February 2, 2011
Are luxury goods normal goods or just not necessities?
Explain your answer.
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CHECKPOINT 5.3
Solution
To know whether a good is a normal good we need to
calculate the income elasticity of demand.
A normal good is a good that has a positive income
elasticity of demand.
The source of the increase in the quantity of luxury good
bought is rising incomes and people spending past
savings.
So the income elasticity of demand is positive. Luxury
good are normal goods.
© 2013 Pearson