# CHAPTER 5 Elasticity

PowerPoint® Slides by Can Erbil
© 2004 Worth Publishers, all rights reserved

What you will learn in this chapter:
What is the definition of elasticity? What is the meaning and importance of price elasticity of demand? income elasticity of demand and? price elasticity of supply? What factors influence the size of these various elasticities? How elasticity affects the incidence of a tax, the measure of who bears its burden?
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Defining and Measuring Elasticity
The price elasticity of demand is the ratio of the percent change in the quantity demanded to the percent change in the price as we move along the demand curve.

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The Price Elasticity of Demand

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The World Demand for Oil
When price rises to \$21 per barrel, world demand falls to 9.9 million barrels per day (point B). At a price of \$20 per barrel, the world quantity of oil demanded is 10 million barrels per day (point A).

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Calculating the price elasticity of demand for oil

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Using the Midpoint Method to Calculate Elasticities
The midpoint method is a technique for calculating the percent change. In this approach, we calculate changes in a variable compared with the average, or midpoint, of the starting and final values.

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Using the Midpoint Method to Calculate Elasticities

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Using the Midpoint Method to Calculate Elasticities – numerical example

= %20 = %20

=1

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Some Estimated Price Elasticities of Demand
Good Inelastic demand Eggs Beef Stationery Gasoline Elastic demand Housing Restaurant meals Airline travel Foreign travel 1.2 2.3 2.4 4.1 0.1 0.4 0.5 0.5 Price elasticity

Price elasticity of demand < 1

Price elasticity of demand > 1
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Interpreting the Price Elasticity of Demand: How Elastic Is Elastic?
Two Extreme Cases of Price Elasticity of Demand Demand is perfectly inelastic when the quantity demanded does not respond at all to the price. When demand is perfectly inelastic, the demand curve is a vertical line. Demand is perfectly elastic when any price increase will cause the quantity demanded to drop to zero. When demand is perfectly elastic, the demand curve is a horizontal line.
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Interpreting the Price Elasticity of Demand: How Elastic Is Elastic?
Unit-Elastic Demand, Inelastic Demand, and Elastic Demand

Demand is elastic if the price elasticity of demand is greater than 1, inelastic if the price elasticity of demand is less than 1, and unit-elastic if the price elasticity of demand is exactly 1.

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Highway department charges for crossing a bridge

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Why does it matter whether demand is unit-elastic, inelastic, or elastic?
Because this classification predicts how changes in the price of a good will affect the total revenue earned by producers from the sale of that good. The total revenue is defined as the total value of sales of a good, i.e. Total revenue = Price × quantity sold

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Elasticity and Total Revenue
When a seller raises the price of a good, there are two countervailing effects in action (except in the rare case of a good with perfectly elastic or perfectly inelastic demand): ■ A price effect: After a price increase, each unit sold sells at a higher price, which tends to raise revenue. ■ A sales effect: After a price increase, fewer units are sold, which tends to lower revenue.
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Elasticity and Total Revenue
If demand for a good is elastic (the price elasticity of demand is greater than 1), an increase in price reduces total revenue. In this case, the sales effect is stronger than the price effect. If demand for a good is inelastic (the price elasticity of demand is less than 1), a higher price increases total revenue. In this case, the price effect is stronger than the sales effect. If demand for a good is unit-elastic (the price elasticity of demand is 1), an increase in price does not change total revenue. In this case, the sales effect and the price effect exactly offset each other.
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The Price Elasticity of Demand Changes Along the Demand Curve
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What Factors Determine the Price Elasticity of Demand? Whether Close Substitutes Are Available Whether the Good Is a Necessity or a Luxury Time

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Other Demand Elasticities: Cross-Price Elasticity
The cross-price elasticity of demand between two goods measures the effect of the change in one good’s price on the quantity demanded of the other good. It is equal to the percent change in the quantity demanded of one good divided by the percent change in the other good’s price.
The Cross-Price Elasticity of Demand Between Goods A and B:

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Cross-Price Elasticity
Goods are substitutes when the cross-price elasticity of demand is positive. Goods are complements when the cross-price elasticity of demand is negative.

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The Income Elasticity of Demand
The income elasticity of demand is the percent change in the quantity of a good demanded when a consumer’s income changes divided by the percent change in the consumer’s income.

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Normal goods and inferior goods
When the income elasticity of demand is positive, the good is a normal good — that is, the quantity demanded at any given price increases as income increases. When the income elasticity of demand is negative, the good is an inferior good — that is, the quantity demanded at any given price decreases as income increases.

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Measuring the Price Elasticity of Supply
The price elasticity of supply is a measure of the responsiveness of the quantity of a good supplied to the price of that good. It is the ratio of the percent change in the quantity supplied to the percent change in the price as we move along the supply curve.

Next two slides: Two Extreme Cases of Price Elasticity of Supply…
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What Factors Determine the Price Elasticity of Supply?
The Availability of Inputs: The price elasticity of supply tends to be large when inputs are easily available. It tends to be small when inputs are difficult to obtain. Time: The price elasticity of supply tends to become larger as producers have more time to respond to a price change. This means that the long-run price elasticity of supply is often higher than the short-run elasticity.

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Economics in Action:
“European Farm Surpluses” Imposition of a price floors to support the incomes of farmers has created “butter mountains” and “wine lakes” in Europe. Were European politicians unaware that their price floors would create huge surpluses? They probably knew that surpluses would arise, but underestimated the price elasticity of agricultural supply due to availability of inputs. They thought big increases in production were unlikely since there was little new land available in Europe for cultivation. However, farm production could expand by adding other resources, especially fertilizer and pesticides. So although farm acreage didn’t increase much, farm production did!
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Elasticity and the Incidence of Excise Tax
When the price elasticity of demand is higher than the price elasticity of supply, an excise tax falls mainly on the producers. When the price elasticity of supply is higher than the price elasticity of demand, an excise tax falls mainly on consumers. So elasticity—not who literally pays the tax—determines the incidence of an excise tax.

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An Excise Tax Paid Mainly by Consumers

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An Excise Tax Paid Mainly by Producers

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The End of Chapter 5
coming attraction: Chapter 6: Consumer and Producer Surplus

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