Elasticity in Microeconomics

Introduction to Elasticity

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

• Price Elasticity of Demand: Measures responsiveness of quantity demanded to changes in price.

• Income Elasticity of Demand: Measures responsiveness of quantity demanded to changes in consumer income.

• Cross Elasticity of Demand: Measures responsiveness of quantity demanded to changes in the price of substitutes or complements.

• Elasticity of Supply: Measures responsiveness of quantity supplied to changes in 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:

• To calculate, use the average price and average quantity to ensure consistency regardless of direction of change.

• Elasticity is a ratio of percentages, making it independent of units of measurement.

Interpreting Elasticity Values

• Elastic Demand: Elasticity > 1. Quantity demanded is highly responsive to price changes.

• Inelastic Demand: Elasticity < 1. Quantity demanded is less responsive to price changes.

• Unit Elastic Demand: Elasticity = 1. Percentage change in quantity equals percentage change in price.

• Perfectly Inelastic Demand: Elasticity = 0. Quantity demanded does not change with price.

• Perfectly Elastic Demand: Elasticity = ∞. Quantity demanded changes infinitely with a tiny price change.

Graphical Representation

• Vertical demand curve: perfectly inelastic.

• Horizontal demand curve: perfectly elastic.

• Downward-sloping linear demand curve: elasticity varies along the curve (elastic above midpoint, unit elastic at midpoint, inelastic below midpoint).

Factors Influencing Price Elasticity of Demand

• Closeness of Substitutes: More substitutes make demand more elastic.

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

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

Total Revenue and Elasticity

Total revenue is the product of price and 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

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

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

• If a price cut leaves total revenue unchanged, demand is unit elastic.

Income Elasticity of Demand

Definition and Calculation

The income elasticity of demand measures how the quantity demanded of a good responds to changes in consumer income.

• If elasticity > 1: demand is income elastic; the good is a normal good (luxury).

• If 0 < elasticity < 1: demand is income inelastic; the good is a normal good (necessity).

• If elasticity < 0: the good is an inferior good (demand decreases as income rises).

Cross Elasticity of Demand

Definition and Calculation

The cross elasticity of demand measures the responsiveness of demand for a good to a change in the price of a substitute or complement.

• Positive cross elasticity: goods are substitutes.

• Negative cross elasticity: goods are complements.

Elasticity of Supply

Definition and Calculation

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

Types of Supply Elasticity

• 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: Easier substitution among resources increases elasticity.

• Time Frame for Supply Decision:

  • Momentary supply: Perfectly inelastic; immediate response to price change.

  • Short-run supply: Somewhat elastic; limited adjustment possible.

  • Long-run supply: Most elastic; full adjustment possible.

Summary Table: Elasticity Types

Key Conclusions

• Understand the concept of elasticity and its importance in market analysis.

• Define and calculate different price elasticities.

• Apply elasticity of demand to analyze total revenue changes.

• Recognize the determinants and implications of price elasticity of supply.

• Interpret what income elasticity of demand reveals about goods.

Additional info: Examples and graphical illustrations (pizza demand curve, total revenue curve) reinforce the calculation and interpretation of elasticity in real-world scenarios.