Overview
The lecture explains the concept of price elasticity of demand, emphasizing its importance, calculation using percent changes, and how elasticity varies along a linear demand curve.
Price Elasticity of Demand: Concept & Importance
- The demand curve slopes downward because lower prices lead to higher quantity demanded.
- Price elasticity of demand (Ep) measures how sensitive quantity demanded is to a change in price.
- Slope of the demand curve depends on units and isn't useful for comparing different goods.
- Using percent changes allows for meaningful comparison across different products.
Calculating Elasticity
- Price elasticity of demand = percent change in quantity demanded / percent change in price.
- Elasticity is usually expressed in absolute value (ignore the negative sign).
- If |Ep| > 1, demand is elastic (quantity demanded changes a lot for a given price change).
- If |Ep| < 1, demand is inelastic (quantity demanded changes little for a given price change).
- If |Ep| = 1, demand is unit elastic (quantity and price change by the same percentage).
Examples & Intuition
- Example demand curve: Q = 1000 - 100P.
- At high prices, a small price drop leads to a large percentage increase in quantity (elastic).
- At low prices, the same absolute price drop leads to a much smaller percentage change in quantity (inelastic).
- The elasticity changes along a straight-line demand curve even though the slope is constant.
- The midpoint of the demand curve is where demand is unit elastic.
Key Terms & Definitions
- Price Elasticity of Demand (Ep) — A measure of how much quantity demanded responds to a price change, calculated as a percent change.
- Elastic Demand — When |Ep| > 1; quantity demanded is very responsive to price.
- Inelastic Demand — When |Ep| < 1; quantity demanded is not very responsive to price.
- Unit Elastic — When |Ep| = 1; percentage change in quantity equals percentage change in price.
- Midpoint Formula — A method for calculating elasticity between two points; not emphasized in this course.
Action Items / Next Steps
- Review the intuition behind elasticity and the effect of price changes at different points on a demand curve.
- Prepare for more detailed discussion on demand elasticity in the next lecture.