3-2 Chapter Outline Elasticity of Demand Alternative Ways of Understanding Elasticity More on Elasticity Consumer and Producer Surplus Kick It Up a Notch: Deadweight Loss
3-3 Elasticity Elasticity: the responsiveness of quantity to a change in another variable Price Elasticity of Demand: the responsiveness of quantity demanded to a change in price Price Elasticity of Supply: the responsiveness of quantity supplied to a change in price Income Elasticity of Demand: the responsiveness of quantity demanded to a change in income Cross Price Elasticity of Demand: the responsiveness of quantity demanded of one good to a change in the price of another good
3-4 The Mathematical Representation of Elasticity Elasticity = %ΔQ %ΔP = ΔQ ΔP Q P Because the demand curve is downward sloping and the supply curve is upward sloping the elasticity of demand is negative and the elasticity of supply is positive. Often these signs are implicit and ignored.
3-5 Elasticity Labels Elastic : the condition of demand when the percentage change in quantity is larger than the percentage change in price Inelastic: the condition of demand when the percentage change in quantity is smaller than the percentage change in price Unitary Elastic: the condition of demand when the percentage change in quantity is equal to the percentage change in price
3-6 Alternative Ways to Understand Elasticity The Graphical Explanation
3-7 The Relationship Between Slope and Elasticity Elasticity and the slope of the demand curve are not the same but they are related. At a given price level, elasticity is greater with a flatter demand curve. With a linear demand curve (meaning a demand curve that has a single value for the slope) elasticity is greater at higher prices.
3-10 Figure 3 Higher Prices Means Greater Elasticity Demand Q/t P B A C D 12.5% change (9-8)/8 25% change (4-3)/4 50% change (3-2)/2 9.1% change (11-10)/11
3-11 Alternative Ways to Understand Elasticity A good for which there are no good substitutes is likely to be one for which you must pay whatever price is charged. It is also likely to be one for which a lower price will not induce substantially greater consumption. Thus, as price changes there is very little change in consumption, i.e. demand is inelastic and the demand curve is steep. Inexpensive goods that take up little of your income can change in price and your consumption will not change dramatically. Thus, at low prices, demand is inelastic. The Verbal Explanation
3-12 Seeing Elasticity Through Total Expenditures Total Expenditure Rule: if the price and the amount you spend both go in the same direction then demand is inelastic while if they go in opposite directions demand is elastic.
3-13 Determinants of Elasticity Number of and Closeness of Substitutes The more alternatives you have the less likely you are to pay high prices for a good and the more likely you are to settle for something that will do. Time The longer you have to come up with alternatives to paying high prices the more likely it is you will shift to those alternatives. Portion of the Budget The greater the portion of the budget an item takes up, the greater the elasticity is likely to be.
3-14 Extremes of Elasticity Perfectly Inelastic: the condition of demand when price changes have no effect on quantity Perfectly Elastic: the condition of demand when price cannot change
3-15 Elasticity and the Demand Curve How the Elasticity of Demand Affects Reactions to Price Changes
3-16 Figure 4 Perfectly Inelastic Demand D Q/t P S2S2 Q 1 =Q 2 P2P2 S1S1 P1P1
3-17 Figure 5 Perfectly Elastic Demand Q/t P D S2S2 P 1 =P 2 Q2Q2 S1S1 Q1Q1
3-18 Figure 6 Inelastic Demand (at moderate prices) P Q/t D S1S1 P1P1 Q1Q1 Q2Q2 S2S2 P2P2
3-19 Figure 7 Elastic Demand (at moderate prices) Q/t P Q1Q1 D S1S1 P1P1 S2S2 P2P2 Q2Q2
3-20 Elasticity Examples Inelastic GoodsPrice Elasticity Eggs0.06 Food0.21 Health Care Services0.18 Gasoline (short-run)0.08 Gasoline (long-run)0.24 Highway and Bridge Tolls0.10 Unit Elastic Good (or close to it) Shellfish0.89 Cars1.14 Elastic Goods Luxury Car3.70 Foreign Air Travel1.77 Restaurant Meals2.27
3-21 Price Elasticity Supply Identical in concept to elasticity of demand. Formula is the Same It is also related to the slope of the supply curve but is not simply the slope of the supply curve. Terminology is the same
3-22 S Q/t P D2D2 Q 1 =Q 2 P2P2 D1D1 P1P1 Perfectly Inelastic Supply
3-23 P Q/t P1P1 Q1Q1 Q2Q2 P2P2 S D2D2 D1D1 Inelastic Supply
3-24 Q/t P Q1Q1 P1P1 P2P2 Q2Q2 S D2D2 D1D1 Elastic Supply
3-25 Q/t P P 1 =P 2 Q2Q2 Q1Q1 S D2D2 D1D1 Perfectly Elastic Supply
3-26 Consumer and Producer Surplus Consumer Surplus: the value you get that is in excess of what you pay to get it On a graph, consumer surplus is the area below the demand curve and above the price line. Producer Surplus: the money the firm gets that is in excess of its marginal costs On a graph, producer surplus is the area below the price line and above the supply curve.
3-27 Figure 12 Value to the Consumer: OACQ* Q/t P 0 Supply Demand P* Q* A B C
3-28 Figure 12 Money Consumers Pay Producers: OP*CQ* P Q/t 0 Supply Demand P* Q* A B C
3-29 Figure 12 Consumer Surplus: P*AC C P Q/t 0 Supply Demand P* Q* A B Value to the Consumer Amount Consumer pays producer Consumer Surplus = minus=
3-30 Figure 13 Variable Cost to the Producer: OBCQ* P 0 Supply Demand P* Q* A B C
3-31 P Q/t 0 Supply Demand P* Q* A B C Amount consumer pays producer Variable cost to producer Producer Surplus =minus = Figure 13 Producer Surplus: BP*C
3-32 P Q/t 0 Supply Demand P* Q* A B C Consumer Surplus Producer Surplus Figure 14 Net Benefit to Society = CS+PS: BAC
3-33 Market Failure Market Failure: the circumstance where the market outcome is not the economically efficient outcome Possible Sources: Consumption or production can harm an innocent third party. A good may not be one for which a company can profit from selling it though society profits from its existence. The buyer may not be able to make a well-informed choice. A buyer or seller may have too much power over the price.
3-34 Categorizing Goods: Exclusivity and Rivalry Exclusivity: the degree to which the consumption of the good can be restricted by a seller to only those who pay for it Rivalry: the degree to which one persons consumption reduces the value of the good for the next consumer
3-35 Private and Public Goods Purely private good: a good with the characteristics of both exclusivity and rivalry Purely public good: a good with the neither of the characteristics exclusivity and rivalry Excludable public good: a good with the characteristic of exclusivity but not of rivalry Congestible public good: a good with the characteristic of rivalry but not of exclusivity
3-36 Kick it Up a Notch Consumer and Producer Surplus in a Supply and Demand Model
3-37 The Optimality of Equilibrium and Dead Weight Loss At equilibrium the sum of producer and consumer surplus is as big as it can be (ABC). Away from equilibrium the sum of producer and consumer surplus is smaller. The degree to which it is smaller is called the dead weight loss. That is, it is the loss in societal welfare associated with production being too little or too great.
3-38 Figure 16 Dead Weight Loss When the Price is Above P* Q/t P Demand Supply A C 0 Q Q* E F P P* B Value to the Consumer: 0AEQ Consumers Pay Producers: OPEQ The Variable Cost to Producers: OBFQ Consumer Surplus: PAE Producer Surplus: BPEF DWL FEC
3-39 Figure 17 Dead Weight Loss When the Price is Below P* Q/t P Demand Supply A P* C 0 Q Q* E F P B Value to the Consumer: 0AEQ Consumers Pay Producers: OPFQ The Variable Cost to Producers: OBFQ Consumer Surplus: PAEF Producer Surplus: BPF DWL FEC