Comprehensive Notes on Price Elasticity of Demand

Introduction

  • Discusses the concept of price elasticity of demand and how it relates to total revenue.
  • Total revenue is influenced by changes in price and quantity demanded.

Price Elasticity of Demand

  • Definition: Price elasticity of demand (PED) measures the responsiveness of quantity demanded to a change in price.
    • Calculated as: ext{PED} = rac{ ext{Percentage change in quantity demanded}}{ ext{Percentage change in price}}

Calculating Percentage Changes

  • To calculate percentage change, observe changes in quantity and price, expressing them as a proportion of some base quantity.
    • Example: If quantity demanded changes from 200 units to 400 units, and price changes from $10 to $8:
    • Quantity change: ext{Percentage change} = rac{400 - 200}{ ext{base quantity}}
    • Price change: ext{Percentage change} = rac{8 - 10}{ ext{original price}}
  • Use midpoint method for accuracy to avoid different elasticity measures depending on direction of change:
    • Midpoint for quantity = rac{200 + 400}{2}
    • Midpoint for price = rac{10 + 8}{2}

Example Calculation

  • Scenario: Price decreases from $10 to $8; quantity increases from 200 to 400.
  • Calculate:
    • Base quantity = 300, while base price = 9.
    • Price change percentage = rac{10 - 8}{9} = rac{2}{9} ext{ or approximately } 0.222
    • Quantity change percentage = rac{400 - 200}{300} = rac{200}{300} ext{ or approximately } 0.667
  • Compute elasticity:
    • ext{PED} = rac{0.667}{0.222} = 3 (Elastic demand)

Implications of Elasticity

  • If elastic (PED > 1), lowering price increases total revenue; if inelastic (PED < 1), increasing price raises total revenue.
  • Total revenue computed as:
    • At $10, total revenue = 10 imes 200 = 2000
    • At $8, total revenue = 8 imes 400 = 3200

Comparison Between Elasticity and Slope

  • Elasticity relates to responsiveness (percentages) while slope measures change per unit.
    • For downward-slope demand curves, higher prices yield lower quantities.
  • As one moves down the demand curve, the elasticity changes.

Perfectly Inelastic and Perfectly Elastic Demand

  • Perfectly Inelastic Demand: Quantity demanded does not change regardless of price changes.
    • Demand curve is vertical; elasticity = 0.
  • Perfectly Elastic Demand: Any price increase results in zero quantity demanded.
    • Demand curve is horizontal; elasticity approaches infinity.

Characteristics Influencing Price Elasticity of Demand

  1. Necessities vs. Luxuries: Necessities (e.g., life-saving drugs) tend to have inelastic demand; luxuries (e.g., gourmet chocolate) are elastic.
  2. Availability of Substitute Goods: More substitutes available indicate higher elasticity
  3. Broad vs. Narrow Definitions: Narrowly defined goods usually have more elastic demand; broadly defined goods have inelastic demand.
    • Example: Food (necessity) is less elastic than gourmet food (non-necessity).
  4. Proportion of Income Spent: Goods that comprise a larger share of a budget will usually have more elastic demand compared to those that constitute a tiny share.
    • Example: Rent versus salt.
  5. Time Horizon: Demand elasticity can increase over time as consumers adjust their behavior.
    • Short-term elasticities are generally smaller compared to long-term elasticities.

Conclusion and Real-World Applications

  • Understanding elasticity helps businesses and economists predict consumer behavior in response to price changes.
  • In real life, market conditions may vary; elasticity calculations serve only as models depending on assumptions made about demand curves.
  • Students encouraged to practice elasticity calculations for various examples to build solid understanding.