弹性及其应用经济学原理曼昆中英文双语.ppt

Elasticity and Its Application弹性及其应用Chapter 5Elasticity . . . 弹性…u … is a measure of how much buyers and sellers respond to changes in market conditions. …是衡量买者和卖者对市场条件变动的反应大小的指标u … allows us to analyze supply and demand with greater precision.…使我们可以更精确地分析供给与需求Price Elasticity of DemanduPrice elasticity of demand is the percentage change in quantity demanded given a percent change in the price. uIt is a measure of how much the quantity demanded of a good responds to a change in the price of that good.需求的价格弹性u需求的价格弹性——价格变化1%引起的需求量的变化百分比值。

u它是一种物品的需求量对其价格变动的反应程度的衡量Determinants of Price Elasticity of Demand需求价格弹性的决定因素uNecessities versus Luxuries 必需品与奢侈品uAvailability of Close Substitutes 相近替代品的可获得性uDefinition of the Market 市场的定义uTime Horizon 时间的长短Determinants of Price Elasticity of DemandDemand tends to be more elastic :nif the good is a luxury.nthe longer the time period.nthe larger the number of close substitutes.nthe more narrowly defined the market.价格需求弹性的决定因素需求倾向于富有弹性：n如果物品是奢侈品n时期更长n相近替代品的数量更多n市场定义的范围更窄Computing the Price Elasticity of DemandThe price elasticity of demand is computed as the percentage change in the quantity demanded divided by the percentage change in price.计算需求价格弹性用需求量变动的百分比除以价格变动的百分比来计算需求价格弹性。

Computing the Price Elasticity of DemandExample: 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:计算需求价格弹性例子: 如果冰激凌蛋卷的价格从2美元上升到2.2美元，你的购买量从10个下降到8个，你的需求价格弹性计算如下：The Midpoint Method: A Better Way to Calculate Percentage Changes and ElasticitiesThe midpoint formula is preferable when calculating the price elasticity of demand because it gives the same answer regardless of the direction of the change.中点法:一种计算百分比变化和弹性的更好方法中点法 是计算需求价格弹性的更好方法，因为无论变动的方向如何，中点法给出了同一个答案。

The Midpoint Method: A Better Way to Calculate Percentage Changes and ElasticitiesExample: 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 the your elasticity of demand, using the midpoint formula, would be calculated as:中点法:一种计算百分比变化和弹性的更好方法例子:如果冰激凌蛋卷的价格从2美元上升到2.2美元，你的购买量从10个下降到8个，利用中点法你的需求价格弹性计算如下：The Variety of Demand CurvesInelastic DemanduQuantity demanded does not respond strongly to price changes.uPrice elasticity of demand is less than one.Elastic DemanduQuantity demanded responds strongly to changes in price.uPrice elasticity of demand is greater than one.多种需求曲线缺乏弹性的需求u需求量不随着价格变化而强烈变化。

u需求价格弹性小于1富有弹性的需求u需求量随着价格变化而强烈变化u需求价格弹性大于1Computing the Price Elasticity of Demand计算需求的价格弹性Demand is price elastic需求富有弹性$54Demand需求Quantity数量1000Price价格50The Variety of Demand CurvesuPerfectly InelasticQuantity demanded does not respond to price changes.uPerfectly ElasticQuantity demanded changes infinitely with any change in price.uUnit ElasticQuantity demanded changes by the same percentage as the price.多种需求曲线u完全无弹性 需求量不随价格变化而变化u完全弹性 价格极小变化引起需求量极大变动u单位弹性 需求量与价格同比例变动A Variety of Demand Curves多种需求弹性曲线Because the price elasticity of demand measures how much quantity demanded responds to the price, it is closely related to the slope of the demand curve.由于需求的价格弹性衡量需求量对价格变化的反应程度，所以它与需求曲线的斜率密切相关。

Perfectly Inelastic Demand— Elasticity equals 0完全无弹性的需求——弹性等于0Quantity 数量Price价格4$5Demand 需求1002. ...leaves the quantity demanded unchanged.2….需求量不变1. Anincreasein price...1.价格上升…Inelastic Demand—— Elasticity is less than 1缺乏弹性的需求——弹性小于1Quantity 数量Price价格4$51. A 22%increasein price...1.价格上升22％…Demand 需求100902. ...leads to a 11% decrease in quantity.2….使需求量减少11%Unit Elastic Demand—— Elasticity equals 1单位需求弹性——弹性等于1Quantity 数量Price价格4$51. A 22%increasein price...1.价格上升22％…Demand 需求100802. ...leads to a 22% decrease in quantity.2….使需求量减少22％。

Elastic Demand—— Elasticity is greater than 1富有弹性的需求——弹性大于1Quantity 数量Price价格4$51. A 22%increasein price...1.价格上升22％…Demand需求100502. ...leads to a 67% decrease in quantity.2….使需求量减少67％Perfectly Elastic Demand- Elasticity equals infinityQuantityPriceDemand$41. At any priceabove $4, quantitydemanded is zero.2. At exactly $4,consumers willbuy any quantity.3. At a price below $4,quantity demanded is infinite.完全富有弹性——弹性等于无穷大数量价格需求$41.在任何高于4美元价格时，2.需求量为02. 在价格正好为4美元时，消费者将购买任何一种数量3. 价格低于4美元时，需求量是无限的。

Total Revenue and the Price Elasticity of Demand 总收益与需求价格弹性uTotal revenue is the amount paid by buyers and received by sellers of a good. 总收益是一种物品买者的支付量和卖者得到的量uComputed as the price of the good times the quantity sold.用该物品的价格乘以销售量来计算TR = P x Q$4Demand 需求Quantity数量P0Price价格P x Q = $400 (total revenue 总收益)100QTotal Revenue and the Price Elasticity of Demand 总收益与需求价格弹性Elasticity and Total Revenue along a Linear Demand Curve 沿着线性需求曲线的弹性与总收益With an inelastic demand curve, an increase in price leads to a decrease in quantity that is proportionately smaller. Thus, total revenue increases. 如果需求是缺乏弹性的，价格上升导致需求量减少的比例小于价格上升的比例，所以总收益是增加的。

Figure 3 How Total Revenue Changes When Price Changes: Inelastic Demand$3Quantity0Price80Revenue = $240 Demand$1DemandQuantity0Revenue = $100100 PriceAn increase in price from $1 to $3...…leads to an increase in total revenue from$100 to $240图3.总收益如何随着价格变化而变化： 缺乏弹性的需求$3数量0价格80收益=240美元 需求$1需求数量0收益 = 100美元100 价格价格从1美元上升到3美元...…导致总收益从100美元增加到240美元Elasticity and Total Revenue along a Linear Demand Curve 沿着线性需求曲线的弹性与总收益With an elastic demand curve, an increase in the price leads to a decrease in quantity demanded that is proportionately larger. Thus, total revenue decreases.如果需求富有弹性，价格上升导致的需求量减少的比例大于价格上升的比例，因此总收益是减少的。

Figure 4 How Total Revenue Changes When Price Changes: Elastic DemandDemandQuantity0Price$450DemandQuantity0PriceRevenue = $100 $520Revenue = $200 An increase in price from $4 to $5...…leads to a decrease in total revenue from$200 to $100图4.总收益如何随着价格变化而变化： 富有弹性的需求需求数量0价格$450数量数量0价格收益 = 100美元 $520收益 =200美元 价格从4美元上升到5美元……导致总收益从200美元减少到100美元the Elasticity of a Linear Demand Curve线性需求曲线的弹性Income Elasticity of DemanduIncome elasticity of demand measures how much the quantity demanded of a good responds to a change in consumers’ income. uIt is computed as the percentage change in the quantity demanded divided by the percentage change in income.需求的收入弹性u需求的收入弹性 衡量消费者收入变动时需求量如何变动。

u它是需求量变动的百分比除以收入变动的百分比 Computing Income Elasticity计算收入弹性Income Elasticityof Demand需求的收入弹性Percentage Change in Quantity DemandedPercentage Change in Income收入变动百分比=需求量变动百分比Income Elasticity- Types of Goods收入弹性：不同类型的物品uNormal Goods 正常物品uInferior Goods 劣等品uHigher income raises the quantity demanded for normal goodsbut lowers the quantity demanded for inferior goods. 正常物品：收入提高增加需求量；劣等品：收入增加减少需求量Income Elasticity - Types of Goods -1.Goods consumers regard as necessities tend to be income inelasticExamples include food, fuel, clothing, utilities, and medical services.2.Goods consumers regard as luxuries tend to be income elastic.Examples include sports cars, furs, and expensive foods.收入弹性：不同类型的物品u消费者消费的必需品往往收入弹性小 例如：食物、燃油、衣服、医疗服务。

u消费者消费的奢侈品往往收入弹性大例如：运动跑车、皮衣和昂贵物品需求的交叉价格弹性需求的交叉价格弹性物品1需求量变动百分比物品2价格变动百分比=替代品： E>0互补品： E<0无关物品：E＝0Price Elasticity of SupplyuPrice elasticity of supply is the percentage change in quantity supplied resulting from a percent change in price.uIt is a measure of how much the quantity supplied of a good responds to a change in the price of that good.供给的价格弹性u供给价格弹性——价格变动1％引起的供給量的变动百分比值u它是一种物品的供給量对其价格变动的反应程度的衡量Perfectly Inelastic Supply—— Elasticity equals 0完全无弹性的供给：弹性等于0Quantity 数量Price价格4$5Supply 供给1002. ...leaves the quantity supplied unchanged.2. …供給量不变。

1. Anincreasein price...1.价格上升…Inelastic Supply —Elasticity is less than 1缺乏弹性的供给：弹性小于1Quantity 数量Price价格4$51. A 22%increasein price...1.价格上升22％…110100Supply 供给2. ...leads to a 10% increase in quantity.2. …引起供給量增加10％Unit Elastic Supply——Elasticity equals 1单位弹性供给：弹性等于1Quantity 数量Price价格4$51. A 22%increasein price...1.价格上升22％…125100Supply 供给2. ...leads to a 22% increase in quantity.2. …引起供給量增加22％Elastic Supply— Elasticity is greater than 1富有弹性的供给：弹性大于1Quantity 数量Price价格4$51. A 22%increasein price...1.价格上升22％…200100Supply 供给2. ...leads to a 67% increase in quantity.2. …引起供給量增加67％。

Perfectly Elastic Supply— Elasticity equals infinity完全有弹性的供给：弹性等于无穷大Quantity 数量Price价格Supply 供给$41. At any price above $4, quantitysupplied is infinite.1.在任何高于4美元的价格时，供給量无限2. At exactly $4, producers willsupply any quantity.2.在正好为4美元时，生产者供给任何一种数量3. At a price below $4, quantity supplied is zero.3.在价格低于4美元时，供給量为0Determinants of Elasticity of Supplyu Ability of sellers to change the amount of the good they produce.uBeach-front land is inelastic.uBooks, cars, or manufactured goods are elastic.u Time period. uSupply is more elastic in the long run.供给弹性的决定因素u 卖者改变它们生产物品产量的能力u海滩前的土地供给是缺乏弹性的。

u书、汽车或生产的物品供给是富有弹性的u 时间长短 u供给在长期内更富有弹性Computing the Price Elasticity of SupplyThe price elasticity of supply is computed as the percentage change in the quantity supplied divided by the percentage change in price.计算供给价格弹性供给价格弹性等于供給量变动百分比除以价格变动百分比THREE APPLICATIONS OF SUPPLY, DEMAND, AND ELASTICITY 供给、需求与弹性的三个应用uCan good news for farming be bad news for farmers?农业的好消息会是农民的坏消息吗？uWhat happens to wheat farmers and the market for wheat when university agronomists discover a new wheat hybrid that is more productive than existing varieties?当大学的农业科学家培育出能比现有品种更高产的小麦新杂交品种时，种小麦的农民会怎么办？小麦市场又会发生什么变动呢？THREE APPLICATIONS OF SUPPLY, DEMAND, AND ELASTICITY 供给、需求与弹性的三个应用uExamine whether the supply or demand curve shifts. 考察是供给曲线还是需求曲线移动。

uDetermine the direction of the shift of the curve. 考虑曲线向哪个方向移动uUse the supply-and-demand diagram to see how the market equilibrium changes. 用供求图说明市场均衡如何变动3. ...and a proportionately smallerincrease in quantity sold. As a result,revenue falls from $300 to $220.An Increase in Supply in the Market for Wheat$3Quantity of Wheat1000Price ofWheat1. When demand is inelastic,an increase in supply...DemandS1S221102. ...leadsto a large fall in price...3. …以及销售量的小幅度增加结果收益从300美元减少为220美元小麦市场上供给增加$3小麦数量1000小麦价格1.当需求缺乏弹性时，2.供给增加...需求S1S221102. …引起价格的大幅度下降...Compute the Price Elasticity of Supply 计算供给价格弹性Demand is inelastic 需求缺乏弹性56$74123Quantity 数量12246810140Price价格Elasticity is larger than 1.弹性大于1Elasticity isSmaller than 1.弹性小于1Figure 5-5$15123Quantity数量1002005000Price 价格525Elasticity is small(less than 1).Elasticity is large(greater than 1).4Figure 5-7弹性小（<1）弹性大（>1）P2P1Quantity of Oil0Priceof OilDemandS2S1(a) The Oil Market in the Short RunP2P1Quantity of Oil0Priceof OilDemandS2S1(b) The Oil Market in the Long Run2. ...leadsto a largeincreasein price.1. In the long run,when supply anddemand are elastic,a shift in supply...2. ...leadsto a smallincreasein price.1. In the short run, when supplyand demand are inelastic,a shift in supply...Figure 5-9P2P1石油数量0石油价格需求S2S1(a) 短期石油市场P2P1石油数量0石油价格需求S2S1(b) 长期石油市场2. ..引起价格大幅度上升1.在长期中，当供给2.与需求富有弹性时，供3.给移动…2. ..引起价格小幅度上升1.在短期中，当供给和需求缺乏2.弹性时，供给移动…Figure 5-9P2P1Quantity of Drugs0Q2Q1Price ofDrugsDemandS2S1Q2Q1(a) Drug InterdictionQuantity of Drugs0Price ofDrugsSupplyD2D1(b) Drug Education3. ...and reduces the quantity sold.2. ...whichraises theprice...2. ...whichreducesthe price...P1P21. Drug interdiction reducesthe supply of drugs...1. Drug education reducesthe demand for drugs...3. ...and reduces the quantity sold.Figure 5-10P2P1毒品数量0Q2Q1毒品价格需求S2S1Q2Q1(a) 禁毒毒品数量0毒品价格供给D2D1(b) 禁毒教育3. …以及减少了销售量。

2. …提高了价格…2. …降低了价格…P1P21. 禁毒减少了毒品供给…1. 禁毒教育减少了毒品需求…3. …以及减少了销售量 Figure 5-10SummaryuPrice elasticity of demand measures how much the quantity demanded responds to changes in the price. uPrice elasticity of demand is calculated as the percentage change in quantity demanded divided by the percentage change in price.uIf a demand curve is elastic, total revenue falls when the price rises. uIf it is inelastic, total revenue rises as the price rises. 小结u需求价格弹性衡量需求量对价格变动的反应程度 u需求价格弹性等于需求量的变化百分比除以价格的变化百分比。

u如果需求曲线是富有弹性的，总收益随着价格的上升而减少 u如果 需求曲线是缺乏弹性的，总收益随着价格的上升而增加SummarynThe income elasticity of demand measures how much the quantity demanded responds to changes in consumers’ income.nThe cross-price elasticity of demand measures how much the quantity demanded of one good responds to the price of another good.小结n需求的收入弹性衡量需求量对消费者收入变动的反应程度 n需求的交叉弹性衡量一种物品的需求量 对另一种物品价格变动的反应程度SummaryuThe price elasticity of supply measures how much the quantity supplied responds to changes in the price. uIn most markets, supply is more elastic in the long run than in the short run. 小结u供给价格弹性衡量供給量对价格变动的反应程度。

u在大多数市场上，供给在长期中比在短期中更富有弹性SummarynThe price elasticity of supply is calculated as the percentage change in quantity supplied divided by the percentage change in price.nThe tools of supply and demand can be applied in many different types of markets.。