曼昆经济学原理第五章.ppt

5 Elasticity and Its Applications Elasticity . . . … allows us to analyze supply and demand with greater precision. … is a measure of how much buyers and sellers respond to changes in market conditions  THE ELASTICITY OF DEMAND Price elasticity of demand is a measure of how much the quantity demanded of a good responds to a change in the price of that good. Price elasticity of demand is the percentage change in quantity demanded given a percent change in the price.  The Price Elasticity of Demand and Its Determinants Availability of Close Substitutes Necessities versus Luxuries Definition of the Market Time Horizon The Price Elasticity of Demand and Its Determinants Demand tends to be more elastic : the larger the number of close substitutes. if the good is a luxury. the more narrowly defined the market. the longer the time period. Computing the Price Elasticity of Demand The price elasticity of demand is computed as the percentage change in the quantity demanded divided by the percentage change in price. Computing the Price Elasticity of Demand Example: If the price of an ice cream cone increases from $2.00 to $2.20 and the amount you buy falls from 10 to 8 cones, then your elasticity of demand would be calculated as: The Midpoint Method: A Better Way to Calculate Percentage Changes and Elasticities The midpoint formula is preferable when calculating the price elasticity of demand because it gives the same answer regardless of the direction of the change. The Midpoint Method: A Better Way to Calculate Percentage Changes and Elasticities Example: If the price of an ice cream cone increases from $2.00 to $2.20 and the amount you buy falls from 10 to 8 cones, then your elasticity of demand, using the midpoint formula, would be calculated as: The Variety of Demand Curves Inelastic Demand Quantity demanded does not respond strongly to price changes. Price elasticity of demand is less than one. Elastic Demand Quantity demanded responds strongly to changes in pr