Price Elasticity of Demand

Introduction to Price Elasticity

When supply increases in a market, the equilibrium price typically falls and the equilibrium quantity rises. However, the magnitude of these changes depends on how responsive the quantity demanded is to changes in price. This responsiveness is measured by the concept of elasticity, which is crucial for understanding market dynamics and consumer behavior.

• Responsiveness refers to how much the quantity demanded changes when the price changes.

• Elasticity provides a units-free measure of this responsiveness, making it possible to compare across different goods and markets.

Graphical Illustration: Figure 4.1

Figure 4.1 demonstrates two scenarios in a local pizza market, showing how an increase in supply affects price and quantity depending on the elasticity of demand.

• Scenario (a): Large Price Change, Small Quantity Change

  • Initial price: $20 per pizza; quantity: 10 pizzas/hour.

  • After supply increases, price falls sharply to $5, but quantity rises only slightly to 13 pizzas/hour.

  • This occurs when the demand curve (DA) is steep, indicating inelastic demand.

• Scenario (b): Small Price Change, Large Quantity Change

  • Initial price: $20 per pizza; quantity: 10 pizzas/hour.

  • After supply increases, price falls modestly to $15, but quantity rises significantly to 17 pizzas/hour.

  • This occurs when the demand curve (DB) is flatter, indicating elastic demand.

Key Concepts and Definitions

• Elasticity: A measure of how much one variable responds to changes in another variable, independent of units of measurement.

• Price Elasticity of Demand: The percentage change in quantity demanded divided by the percentage change in price, holding all other influences constant.

Formula:

Comparing Elasticity and Slope

While the slope of a demand curve can indicate responsiveness, it depends on the units used for price and quantity. Elasticity, by contrast, is a unit-free measure, allowing for meaningful comparisons across different goods and markets.

• Steep demand curve (high slope): Indicates inelastic demand—large price changes result in small quantity changes.

• Flat demand curve (low slope): Indicates elastic demand—small price changes result in large quantity changes.

Applications and Examples

• Pizza Market Example: A pizza producer may want to compare the demand for pizza with the demand for soft drinks. Elasticity allows for this comparison, even though the units (pizzas vs. soft drinks) are different.

• Policy Implications: Understanding elasticity helps businesses and policymakers predict the effects of supply changes, taxes, and subsidies on market outcomes.

Summary Table: Effects of Supply Increase Based on Elasticity

Conclusion

The price elasticity of demand is a fundamental concept in microeconomics, providing a standardized way to measure and compare how quantity demanded responds to price changes. This concept is essential for analyzing market outcomes, making business decisions, and formulating economic policy.