This document discusses four types of elasticity: 1. Price elasticity of demand measures how responsive quantity demanded is to price changes. It is calculated by dividing the percentage change in quantity by the percentage change in price. 2. Cross elasticity of demand measures how responsive the quantity demanded of one good is to price changes in another good. It shows if goods are substitutes or complements. 3. Income elasticity of demand measures how responsive quantity demanded is to changes in consumer income. It helps determine if a good is normal, inferior, or a luxury. 4. Price elasticity of supply measures how responsive quantity supplied is to price changes. It depends on factors like time available for producers to adjust supply

1. Elasticity
Chapter 17

2. Price Elasticity of Demand
• A measure of the responsiveness of quantity
demanded to changes in price.
• Measured by dividing the percentage change in the
quantity demanded of a good by the percentage
change in its price.
• Economists compute price elasticity of demand using
midpoints as the base values of changes in prices and
quantities demanded.

3. Computing Elasticity of Demand
We divide the change in quantity demanded by
the average quantity demanded, all of which is
then divided by the change in price divided by
the average price.

4. Perfectly Elastic and Perfectly Inelastic Demand
Percentage change in quantity demanded
Ed
= -------------------------------------------
Percentage change in price
• Elastic Demand (Ed
> 1): the numerator is
greater than the denominator, the
coefficient is greater than 1 and demand is
elastic.
• Inelastic Demand (Ed
< 1): the numerator is
less than the denominator , the coefficient
is less than 1, and demand is inelastic.

5. Calculating price elasticity of Deamnd.
Suppose at a price of $10 the quantity de
manded is 100. When price falls to $8, the
quantity demanded increases to 130.
The absolute value of the price elasticity of
demand betweenthe prices of $10
and $8 is approximately.

6. Perfectly Elastic and Perfectly Inelastic Demand
• Unit Elastic Demand (Ed
= 1): If the numerator and denominator are the same, the
coefficient is equal to one. The quantity demanded changes proportionally to a
change in price.

7. Elastic and Inelastic Demand
• Perfectly Elastic Demand (Ed = ) If the quantity
demanded is extremely responsive to a
change in price.
• Perfectly Inelastic Demand (Ed = 0) If quantity
demanded is completely unresponsive to
changes in price, demand is perfectly inelastic.
A change in price causes no change in quantity
demanded.

8. Price Elasticity of Demand

9. Price Elasticity of Demand and Total
Revenue
• Total Revenue (TR) of a seller equals the price of a good
times the quantity of the good sold.
• Total revenue may increase, decrease or remain constant.
• If demand is elastic, a price rise decreases total revenue.
• If demand is elastic, a price fall increases total revenue.
• If demand is inelastic, a price fall decreases total revenue.
• If demand is unit elastic, a price fall will sell more goods
while total revenue remains constant.

10. Elasticities, Price
Changes and Total
Revenue

11. Price Elasticity of Demand Along a
Demand Curve

12. Determinants of Price Elasticity on Demand
• Number of Substitutes: The more substitutes for a good,
the higher the price elasticity of demand; the fewer
substitutes for a good, the lower the price elasticity of
demand.
• The more broadly defined the good, the fewer the
substitutes; the more narrowly defined the good, the
greater the substitutes.

13. Determinants of Price Elasticity on Demand
• Percentage of One’s Budget Spent on the Good: The
greater the percentage of one’s budget that goes to
purchase a good, the higher the price elasticity of demand;
the smaller the percentage of one’s budget that goes to
purchase a good, the lower the elasticity of demand.
• Time: The more time that passes, the higher the price
elasticity of demand for the good; the less time that passes,
the lower the price elasticity of demand for the good.

14. Cross Elasticity of Demand
• Measures the responsiveness in the quantity
demanded of one good to changes in the price of
another good.
• Defined as the percentage change in the quantity
demanded of one good divided by the percentage
change in the price of another good.
• This concept is often used to determine whether two
goods are substitutes or complements and the
degree to which one good is a complement to or
substitute for another.

15. Income Elasticity of Demand
• Measures the responsiveness of quantity demanded to
changes in income.
• Define as the percentage change in quantity demanded of a
good divided by the percentage change in income.
• Income elasticity of demand is positive (Ey
> 0) for a normal
good.
• The demand for an inferior good decreases as income
increases.
• If Ey
>1, demand is considered to be income elastic.
• If Ey
<1, demand is considered to be income inelastic.
• If Ey
=1, demand is considered to be unit elastic

16. Price Elasticity of Supply
• Measures the responsiveness of quantity
supplied to changes in price.
• Defined as the percentage change in quantity
supplied of a good divided by the percentage
change in the price of the good.
• Supply can be classified as elastic, inelastic,
unit elastic, perfectly elastic, or perfectly
inelastic.

17. Price Elasticity of Supply

18. Price Elasticity of Supply and Time
• The longer the period of adjustment to a
change in price, the higher the price elasticity of
supply.
• Additional production takes time.
• Reducing production takes time.

19. Summary of the Four Elasticity Concepts