Ch. 4: Elasticity.

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Ch. 4: Elasticity. Define, calculate, and explain the factors that influence the own price elasticity of demand the cross price elasticity of demand the income elasticity of demand the elasticity of supply. Demand for parking garage passes. Price Elasticity of Demand.

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Ch. 4: Elasticity.

Define, calculate, and explain the factors that influence

• the own price elasticity of demand
• the cross price elasticity of demand
• the income elasticity of demand
• the elasticity of supply
Price Elasticity of Demand
• Price elasticity of demand
• units-free measure of the responsiveness of the quantity demanded of a good to a change in its price, ceteris paribus.
Price Elasticity of Demand

%DQ = DQ/Qavg

= 2/10

= .2

%DP = DP/Pavg

= -\$1/\$20

= -.05

e = .2/.05 =4

Price Elasticity of Demand
• By using the average price and average quantity, we get the same elasticity value regardless of whether the price rises or falls.
• Measuring as % changes leaves the elasticity value the same (“units free”).
• Although the formula yields a negative value for elasticity because price and quantity move in opposite directions, we report the absolute value.
Price Elasticity of Demand
• Inelastic and Elastic Demand
• if e>1: elastic
• if e=1: unit elastic
• if e<1: inelastic
• Shape of
• Perfectly inelastic demand curve (e=0)
• Perfectly elastic demand curve (e= infinite)
Price Elasticity of Demand

At prices above the mid-point of the demand curve, demand is elastic.

At prices below the mid-point of the demand curve, demand is inelastic.

Price Elasticity of Demand
• Total Revenue and Elasticity
• TR=P*QD
• When P changes, TR could rise or fall because QD moves in opposite direction.
Price Elasticity of Demand
• %D TR = % D P + % D Q

= % D P - % D P(e)

= % D P(1-e)

• If demand is elastic (e>1),

P increase  TR decreases

P decrease  TR increases

• If demand is inelastic (e<1),

P increase  TR increases

P decrease  TR decreases

• If demand is unitary elastic,

P increase or decrease  TR unchanged.

Price Elasticity of Demand
• As P falls from \$25 to \$12.50, D is elastic, and TR rises.
• At \$12.50, D is unit elastic and TR stops increasing.
• As P falls from \$12.50 to 0, D is inelastic, and TR decreases.
Price Elasticity of Demand
• The elasticity of demand for a good depends on:
• The number & closeness of substitutes
• The proportion of income spent on the good
• The time elapsed since a price change
More Elasticities of Demand
• Cross Elasticity of Demand
• measures responsiveness of demand for a good to a change in the price of another good.

exy= %D quantity demanded for x

%D change in price of y

• exy> 0  substitutes
• exy<0  complements
More Elasticities of Demand
• Income Elasticity of Demand
• measures how the quantity demanded of a good responds to a change in income, ceteris paribus. eI = %D in quantity demanded

% D in income

• eI >0  normal good
• eI >1 luxury good
• eI <0 inferior good
Price Elasticity of Supply

A change in demand causes

• A larger change in equilibrium price if supply is supply is steeper,
• A smaller change in equilibrium quantity if supply is steeper.
Elasticity of Supply

Elasticity of supply

• measures the responsiveness of the quantity supplied to a change in the price of a good when all other influences on selling plans remain the same.
Elasticity of Supply
• Factors That Influence the Elasticity of Supply
• Elasticity of supply for inputs
• The time frame for supply decisions
• Storage costs