Elasticity in Microeconomics

Introduction to Elasticity

Elasticity is a fundamental concept in microeconomics that measures the responsiveness of one variable to changes in another. In the context of markets, elasticity helps us understand how quantity demanded or supplied reacts to changes in price, income, or the price of related goods.

• Price Elasticity of Demand: Measures how much the quantity demanded of a good responds to a change in its price.

• Income Elasticity of Demand: Measures how much the quantity demanded of a good responds to a change in consumer income.

• Cross Elasticity of Demand: Measures how much the quantity demanded of a good responds to a change in the price of another good.

• Elasticity of Supply: Measures how much the quantity supplied of a good responds to a change in its price.

Price Elasticity of Demand

Definition and Calculation

The price elasticity of demand is a units-free measure of the responsiveness of the quantity demanded of a good to a change in its price, holding all other factors constant.

• Formula:

• Use average price and average quantity to calculate percentage changes, ensuring the measure is independent of units.

• The sign is typically negative due to the inverse relationship between price and quantity demanded, but the magnitude (absolute value) is used to assess responsiveness.

Types of Price Elasticity of Demand

• Perfectly Inelastic Demand: Elasticity = 0. Quantity demanded does not change as price changes. Demand curve is vertical.

• Unit Elastic Demand: Elasticity = 1. Percentage change in quantity demanded equals percentage change in price. Demand curve has a declining slope.

• Inelastic Demand: Elasticity < 1. Quantity demanded changes less than the price change.

• Elastic Demand: Elasticity > 1. Quantity demanded changes more than the price change.

• Perfectly Elastic Demand: Elasticity = ∞. Any price change leads to an infinite change in quantity demanded. Demand curve is horizontal.

Factors Influencing Price Elasticity of Demand

• Closeness of Substitutes: The more substitutes available, the more elastic the demand.

• Proportion of Income Spent: Goods that take up a larger share of income tend to have more elastic demand.

• Time Elapsed Since Price Change: Demand becomes more elastic over time as consumers adjust.

Elasticity Along a Linear Demand Curve

Elasticity varies along a straight-line demand curve:

• Above the midpoint: Demand is elastic.

• At the midpoint: Demand is unit elastic.

• Below the midpoint: Demand is inelastic.

Total Revenue and Elasticity

Total revenue is calculated as price multiplied by quantity sold. The effect of a price change on total revenue depends on the elasticity of demand:

• If demand is elastic, a price cut increases total revenue.

• If demand is inelastic, a price cut decreases total revenue.

• If demand is unit elastic, total revenue remains unchanged.

Total Revenue Test: Observing changes in total revenue after a price change can help estimate elasticity.

Consumer Expenditure and Elasticity

• If your demand is elastic, a price cut increases your expenditure.

• If your demand is inelastic, a price cut decreases your expenditure.

• If your demand is unit elastic, your expenditure does not change.

More Elasticities of Demand

Income Elasticity of Demand

Measures the responsiveness of quantity demanded to changes in income.

• Formula:

• If elasticity > 1: Demand is income elastic; the good is a normal good.

• If 0 < elasticity < 1: Demand is income inelastic; the good is a normal good.

• If elasticity < 0: The good is an inferior good.

Cross Elasticity of Demand

Measures the responsiveness of demand for a good to changes in the price of a substitute or complement.

• Formula:

• Substitutes: Cross elasticity is positive.

• Complements: Cross elasticity is negative.

Elasticity of Supply

Definition and Calculation

The elasticity of supply measures the responsiveness of quantity supplied to a change in price, holding all other factors constant.

• Formula:

Types of Elasticity of Supply

• Perfectly Inelastic Supply: Elasticity = 0. Supply curve is vertical.

• Unit Elastic Supply: Elasticity = 1. Supply curve is linear and passes through the origin.

• Perfectly Elastic Supply: Elasticity = ∞. Supply curve is horizontal.

Factors Influencing Elasticity of Supply

• Resource Substitution Possibilities: The easier it is to substitute resources, the greater the elasticity.

• Time Frame for Supply Decision:

  • Momentary supply: Perfectly inelastic; quantity supplied is fixed immediately after a price change.

  • Short-run supply: Somewhat elastic.

  • Long-run supply: Most elastic.

Glossary of Elasticity Measures

Example Applications

• Price Elasticity Example: If the price of pizza falls from $20.50 to $19.50 and quantity demanded increases from 9 to 11 pizzas per hour, calculate elasticity using the average price and quantity.

• Income Elasticity Example: If income rises and demand for organic food increases, the income elasticity is positive, indicating a normal good.

• Cross Elasticity Example: If the price of burgers (a substitute for pizza) rises and pizza demand increases, cross elasticity is positive.

• Supply Elasticity Example: If the price of wheat rises and farmers can easily switch crops, supply elasticity is high.

Additional info: Some definitions and examples have been expanded for clarity and completeness.