弹性及其应用经济学原理中英文双语课件

1、Elasticity and Its Application弹性及其应用Chapter 5Elasticity . . . 弹性 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。 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 DemandPrice elasticity of d

2、emand is the percentage change in quantity demanded given a percent change in the price. It 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。 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

3、价格弹性的决定因素Necessities versus Luxuries 必需品与奢侈品Availability of Close Substitutes 相近替代品的可获得性Definition of the Market 市场的定义Time Horizon 时间的长短Determinants of Price Elasticity of DemandDemand tends to be more elastic :if the good is a luxury.the longer the time period.the larger the number of close substit

4、utes.the 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：如果物品是奢侈品时期更长相近替代品的数量更多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

5、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 Me

6、thod: 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 Midpoin

7、t 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

8、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 DemandQuantity demanded does not respond strongly to price changes.Price elasticity of demand is less than one.Elastic DemandQuantity demanded responds strongly to changes in price.Price elasticity of demand

9、is greater than one.多种需求曲线缺乏弹性的需求需求量不随着价格变化而强烈变化。需求价格弹性小于1。富有弹性的需求需求量随着价格变化而强烈变化。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50The Variety of Demand CurvesPerfectly InelasticQuantity demanded does not respond to price change

10、s.Perfectly ElasticQuantity demanded changes infinitely with any change in price.Unit ElasticQuantity demanded changes by the same percentage as the price.多种需求曲线完全无弹性 需求量不随价格变化而变化。完全弹性 价格极小变化引起需求量极大变动。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

11、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. Anincrea

12、sein 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22Demand 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22Deman

13、d 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22Demand需求100502. .leads to a 67% decrease in quantity.2.使需求量减少67。Perfectly Elastic Demand- Elasticity equals infinityQuantityPriceDe

14、mand$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$4在任何高于4美元价格时，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

15、性Total 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。Computed 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

16、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 Reven

17、ue 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

18、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 H

19、ow 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

20、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 DemandIncome elasticity of demand measures how much the quantity demanded of a good responds to a change in consumers income. It is computed as the percentage change in the quantity demanded divided by the

21、percentage change in income.需求的收入弹性需求的收入弹性 衡量消费者收入变动时需求量如何变动。 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Normal Goods 正常物品Inferi

22、or Goods 劣等品Higher 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 -Goods consumers regard as necessities tend to be income inelasticExamples include food, fuel, clothing, utiliti

23、es, and medical services.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。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： E0互补品： E0无关物品：E0Price Elasticity of

24、 SupplyPrice elasticity of supply is the percentage change in quantity supplied resulting from a percent change in price.It is a measure of how much the quantity supplied of a good responds to a change in the price of that good.供给的价格弹性供给价格弹性价格变动1引起的供給量的变动百分比值。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 Inela

25、stic 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22110100Supply 供给2. .leads to a 10%

26、 increase in quantity.2. 引起供給量增加10。Unit Elastic SupplyElasticity 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22125100Supply 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%increase

27、in price.1.价格上升22200100Supply 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

28、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 Supply Ability of sellers to change the amount of the good they produce.Beach-front land is inelastic.Books, cars, or manufactured goods are elastic. Time period. Supply

29、is more elastic in the long run.供给弹性的决定因素 卖者改变它们生产物品产量的能力海滩前的土地供给是缺乏弹性的。书、汽车或生产的物品供给是富有弹性的。 时间长短 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

30、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Can good news for farming be bad news for farmers?农业的好消息会是农民的坏消息吗？What happens to wheat farmers and the market for wheat when university agronomists discover a new wheat hybrid that is more productive than existing v

31、arieties?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Examine whether the supply or demand curve shifts. 考察是供给曲线还是需求曲线移动。Determine the direction of the shift of the curve. 考虑曲线向哪个方向移动。Use the supply-and-demand diagram to se

32、e 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.DemandS1S221

33、102. .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小麦价格当需求缺乏弹性时，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

34、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）P2P1Quantity of Oil0Priceof OilDemandS2S1(a) The Oil Market in the Short RunP2P1Quantity of Oil0Priceof OilDemandS2S1(b) The Oil Market in the Long Run2. .leads

35、to 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 5-9P2P1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在长期中，当供给与需

36、求富有弹性时，供给移动2. .引起价格小幅度上升在短期中，当供给和需求缺乏弹性时，供给移动Figure 5-9P2P1Quantity 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 re

37、ducesthe supply of drugs.1. Drug education reducesthe demand for drugs.3. .and reduces the quantity sold.Figure 5-10P2P1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 5-10SummaryPrice elasticity of demand measures how much the quantity dem