1. Elasticity: The Responsiveness of Demand and Supply

2. Do People Care about the Prices of Books?
After studying this chapter, you should be able to:
Define the price elasticity of demand and understand how to calculate it.
Discuss the determinants of the price elasticity of demand.
Understand the relationship between the price elasticity of demand and total revenue.
Define the cross-price elasticity of demand and the income elasticity of demand, and understand how they are calculated and what their main determinants are.
Use price elasticity and income elasticity to analyze economic issues.
Define the price elasticity of supply, and understand how it is calculated and what its main determinants are. 1 2 3 4
LEARNING OBJECTIVES
In this chapter we will see how to measure the responsiveness of the quantity demanded of a product to changes in its price. 5 6

3. Elasticity: The Responsiveness of Demand and Supply
Elasticity A measure of how much one economic variable responds to changes in another economic variable.

4. The Price Elasticity of Demand and Its Measurement
LEARNING OBJECTIVE 1
The Price Elasticity of Demand and Its Measurement
Price elasticity of demand The responsiveness of the quantity demanded to a change in price, measured by dividing the percentage change in the quantity demanded of a product by the percentage change in the product’s price.
Measuring the Price Elasticity of Demand

5. If you know the value for price elasticity of demand, then which of the following can you compute?
a. The effect of a price change on the quantity demanded.
b. The responsiveness of the quantity supplied of a good to changes in its price.
c. The price elasticity of supply.
d. All of the above.

6. If you know the value for price elasticity of demand, then which of the following can you compute?
a. The effect of a price change on the quantity demanded.
b. The responsiveness of the quantity supplied of a good to changes in its price.
c. The price elasticity of supply.
d. All of the above.

7. The Price Elasticity of Demand and Its Measurement
Elastic Demand and Inelastic Demand
Elastic demand Demand is elastic when the percentage change in quantity demanded is greater than the percentage change in price, so the price elasticity is greater than 1 in absolute value.
Inelastic demand Demand is inelastic when the percentage change in quantity demanded is less than the percentage change in price, so the price elasticity is less than 1 in absolute value.
Unit-elastic demand Demand is unit-elastic when the percentage change in quantity demanded is equal to the percentage change in price, so the price elasticity is equal to –1.

8. The Price Elasticity of Demand and Its Measurement
An Example of Computing Price Elasticities
6 - 1
Elastic and Inelastic Demand Curves

9. Refer to the figure below
Refer to the figure below. Which two points belong to the demand curve that is relatively less elastic?
a. Points A and C.
b. Points A and B.
c. Either points A and C or points A and B, since both curves share point A.
d. None of the above.

10. Refer to the figure below
Refer to the figure below. Which two points belong to the demand curve that is relatively less elastic?
a. Points A and C.
b. Points A and B.
c. Either points A and C or points A and B, since both curves share point A.
d. None of the above.

11. The Price Elasticity of Demand and Its Measurement
The Midpoint Formula
Price elasticity of demand =

12. How do economists avoid confusion over units in the computation of elasticity?
a. By using index numbers rather than whole numbers.
b. By using percentage changes rather than simple differences.
c. By using aggregate values rather than single values.
d. By using the same number as the value of the slope of the curve.

13. How do economists avoid confusion over units in the computation of elasticity?
a. By using index numbers rather than whole numbers.
b. By using percentage changes rather than simple differences.
c. By using aggregate values rather than single values.
d. By using the same number as the value of the slope of the curve.

14. QUANTITY (BILLIONS OF BUSHELS)
6 - 1
LEARNING OBJECTIVE 1
Calculating the Price Elasticity of Demand for Wheat Using the Midpoint Formula
YEAR
PRICE (PER BUSHEL)
QUANTITY (BILLIONS OF BUSHELS)
2010
$3.00
3.0
2011
$3.60
2.8
Verify that the price elasticity of demand is –0.4.

15. The Price Elasticity of Demand and Its Measurement
Polar Cases of Perfectly Elastic and Perfectly Inelastic Demand
Perfectly inelastic demand Demand is perfectly inelastic when a change in price results in no change in quantity demanded.
Perfectly elastic demand Demand is perfectly elastic when a change in price results in an infinite change in quantity demanded.

16. If demand is perfectly elastic, then what is the impact of an increase in price?
a. A decrease in quantity demanded to zero.
b. No change in quantity demanded.
c. A change in quantity demanded exactly equal to the change in price.
d. A very small change in quantity demanded.

17. If demand is perfectly elastic, then what is the impact of an increase in price?
a. A decrease in quantity demanded to zero.
b. No change in quantity demanded.
c. A change in quantity demanded exactly equal to the change in price.
d. A very small change in quantity demanded.

18. The Price Elasticity of Demand and Its Measurement
6 – 1
The Price Elasticity of Demand

19. The Price Elasticity of Demand and Its Measurement
6 – 1 (continued)
The Price Elasticity of Demand
Don’t Confuse Inelastic with Perfectly Inelastic

20. When quantity demanded is completely unresponsive to price, what is the value of price elasticity of demand?
a. Zero.
b. 1.
c. A number between zero and 1.
d. A negative number.

21. When quantity demanded is completely unresponsive to price, what is the value of price elasticity of demand?
a. Zero.
b. 1.
c. A number between zero and 1.
d. A negative number.

22. What Determines the Price Elasticity of Demand for a Product?
LEARNING OBJECTIVE 2
What Determines the Price Elasticity of Demand for a Product?
The key determinants of price elasticity of demand are as follows:
Availability of close substitutes
Passage of time
Necessities versus luxuries
Definition of the market
Share of good in the consumer’s budget

23. PRICE ELASTICITY OF DEMAND
6 - 1
The Price Elasticity of Demand for Breakfast Cereal
CEREAL
PRICE ELASTICITY OF DEMAND
Post Raisin Bran
-2.5
All family breakfast cereals
-1.8
All types of breakfast cereals
-0.9
What happens when the price of cereal rises?

24. The Relationship Between Price Elasticity and Total Revenue
LEARNING OBJECTIVE 3
The Relationship Between Price Elasticity and Total Revenue
Total revenue The total amount of funds received by a seller of a good or service, calculated by multiplying price per unit by the number of units sold.
6 - 2
The Relationship Between Price Elasticity and Total Revenue

25. When demand is price-inelastic, what is the relationship between price and total revenue?
a. They move together.
b. They move in opposite directions.
c. They move inversely.
d. They are entirely unrelated.

26. When demand is price-inelastic, what is the relationship between price and total revenue?
a. They move together.
b. They move in opposite directions.
c. They move inversely.
d. They are entirely unrelated.

27. The Relationship Between Price Elasticity and Total Revenue
Elasticity and Revenue with a Linear Demand Curve
6 – 2
The Relationship between Price Elasticity and Revenue
IF DEMAND IS . . .
THEN . . .
BECAUSE . . .
elastic
an increase in price reduces revenue
the decrease in quantity demanded is proportionally greater than the increase in price.
a decrease in price increases revenue
the increase in quantity demanded is proportionally greater than the decrease in price.
inelastic
an increase in price increases revenue
the decrease in quantity demanded is proportionally smaller than the increase in price.
a decrease in price reduces revenue
the increase in quantity demanded is proportionally smaller than the decrease in price.
unit-elastic
an increase in price does not affect revenue
the decrease in quantity demanded is proportionally the same as the increase in price.
a decrease in price does not affect revenue
the increase in quantity demanded is proportionally the same as the decrease in price.

28. The Relationship Between Price Elasticity and Total Revenue
6 - 3
Elasticity is Not Constant Along a Linear Demand Curve

29. 6 - 2
Determining the Price Elasticity of Demand for DVDs by Market Experiment
FILM
DVD PRICE
VHS PRICE
Rugrats in Paris
$22.46
$22.99
The Mummy Returns
$26.98
$22.98
Miss Congeniality
$16.69
The Perfect Storm
$24.98
When DVDs were first introduced, the movie studios were uncertain of their price elasticity of demand.

30. Other Demand Elasticities
LEARNING OBJECTIVE 4
Other Demand Elasticities
Cross-Price Elasticity of Demand
Cross-price elasticity of demand The percentage change in quantity demanded of one good divided by the percentage change in the price of another good.
6 – 3
Summary of Cross-Price Elasticity of Demand
IF THE PRODUCTS ARE . . .
THEN THE CROSS-PRICE ELASTICITY OF DEMAND WILL BE . . .
EXAMPLE
Substitutes
Positive
Two brands of printers
Complements
Negative
Printers and toner cartridges
Unrelated
Zero
Printers and peanut butter

31. Fill in the blanks: If an increase in the price of a substitute leads to __________ in quantity demanded, the cross-price elasticity of demand is _________.
a. an increase; positive
b. an increase; negative
c. a decrease; positive
d. a decrease; negative

32. Fill in the blanks: If an increase in the price of a substitute leads to __________ in quantity demanded, the cross-price elasticity of demand is _________.
a. an increase; positive
b. an increase; negative
c. a decrease; positive
d. a decrease; negative

33. Other Demand Elasticities
Income Elasticity of Demand
Income elasticity of demand A measure of the responsiveness of quantity demanded to changes in income, measured by the percentage change in quantity demanded divided by the percentage change in price.
6 – 4
Summary of Income Elasticity of Demand
IF THE INCOME ELASTICITY OF DEMAND IS . . .
THEN THE GOOD IS . . .
EXAMPLE
Positive, but less than 1
Normal and a necessity
Milk
Positive and greater than 1
Normal and a luxury
Caviar
Negative
Inferior
High-fat meat

34. 6 - 3
Price Elasticity, Cross-Price Elasticity, and Income Elasticity in the Market for Alcoholic Beverages
Price elasticity of demand for beer
-0.23
Cross-price elasticity of demand between beer and wine
0.31
Cross-price elasticity of demand between beer and spirits
0.15
Income elasticity of demand for beer
-0.09
Income elasticity of demand for wine
5.03
Income elasticity of demand for spirits
1.21
An “Inferior Good?”

35. Using Elasticity to Analyze the Disappearing Family Farm
LEARNING OBJECTIVE 5
Using Elasticity to Analyze the Disappearing Family Farm
6 - 4
Elasticity and the Disappearing Farm

36. 6 - 3 Verify that the percentage change in quantity demanded is 1.9%.
LEARNING OBJECTIVE 5
Using Price Elasticity to Analyze the Drug Problem
Verify that the percentage change in quantity demanded is 1.9%.

37. The Price Elasticity of Supply
LEARNING OBJECTIVE 6
The Price Elasticity of Supply
Measuring the Price Elasticity of Supply
Price elasticity of supply The responsiveness of the quantity supplied to a change in price, measured by dividing the percentage change in the quantity supplied of a product by the percentage change in the product’s price.

38. 6 - 4 Why do oil prices fluctuate so much?
Why Are Oil Prices So Unstable?
Why do oil prices fluctuate so much?

39. The Price Elasticity of Supply
Polar Cases of Perfectly Elastic and Perfectly Inelastic Supply
6 – 5
The Price Elasticity of Supply

40. The Price Elasticity of Supply
Polar Cases of Perfectly Elastic and Perfectly Inelastic Supply
The Price Elasticity of Supply
6 – 5 (continued)

41. The Price Elasticity of Supply
Using Price Elasticity of Supply to Predict Changes in Price
6 - 5
Changes in Price Depend on the Price Elasticity of Supply

42. What is the impact of a given shift in demand when supply is relatively more elastic?
a. A smaller increase in price.
b. A larger increase in price.
c. A percentage change in quantity exactly equal to a given percentage change in price.
d. No change in price.

43. What is the impact of a given shift in demand when supply is relatively more elastic?
a. A smaller increase in price.
b. A larger increase in price.
c. A percentage change in quantity exactly equal to a given percentage change in price.
d. No change in price.

44. Amazon, Microsoft Earnings Better than Expected

45. Cross-price elasticity of demand
Elastic demand
Elasticity
Income elasticity of demand
Inelastic demand
Perfectly elastic demand
Perfectly inelastic demand
Price elasticity of demand
Price elasticity of supply
Total revenue
Unit-elastic demand