第2讲 弹性.ppt

1、,第二章Elasticity and Its Application弹性及其应用,据环球时报报道：美国的农业机械化普及程度高，农业基本上以大面积的农场和牧场为主，农业人口500多万，只占总人口的2%左右。这些为数不多的美国农民，不但养活了2.9亿美国人，还使美国成为世界最大的农产品出口国，美国2001年农产品出口高达535亿美元。 美国历届政府对农业的扶持力度都超过制造业等传统行业。政府每年用于农业的开支远远高于来自农业的税收。去年布什政府颁布的新农业法规定，在今后的10年里，政府对农业的各种补贴和财政支持达到1900亿美元，平均每年投入190亿美元。 除税收方面的优惠外，美国农民享受的政府补

2、贴可能是世界上数额最多的。佛蒙特州农业局的政策分析员怀特女士介绍，政府给予农民的补贴主要形式有：低息贷款、差额补贴、休耕补贴和灾害保险补贴等。政府给予农民的补贴到底有多少，具体数额因人而异。据统计，政府通过各种补贴计划，向农民发放的补贴约占其收入的1/4左右。如果把政府每年的补贴平均分摊到农民头上的话，每户每年享受的各类补贴累计高达21万美元。 休耕补贴是政府为了适当限制生产而给予的优惠。如果农场主将20%的耕地休耕用于土壤保护，他可从政府那里得到休耕土地正常产量50%的现金或实物补偿。休耕不仅可以保护耕地，还可以控制产量，保护农产品价格。此外，政府还会根据上一年的销售情况，为避免某一种农产品

3、过剩而制定一些计划来引导农民的耕作。比如，如果政府估计棉花供过于求，就鼓励棉农只耕种3/4的土地，并将1/4休耕地棉花收成折合成现金付给农民。,案例,Figure 8 An Increase in Supply in the Market for Wheat,Copyright2003 Southwestern/Thomson Learning,Quantity of,Wheat,0,Price of,Wheat,p2,q2,p1,q1,Elasticity . . . 弹性, is a measure of how much buyers and sellers respond to cha

4、nges 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 Demand需求的价格弹性,Price elasticity of demand measures the percentage change in the quantity demanded resulting from a 1-percent change in price. 需求的价格弹性

5、价格变化1%引起的需求量变化的百分比值。 It is a measure of how much the quantity demanded of a good responds to a change in the price of that good. 它是一种物品的需求量对其价格变动的反应程度的衡量。,Computing the Price Elasticity of Demand计算需求价格弹性,The price elasticity of demand is computed as the percentage change in the quantity demanded div

6、ided by the percentage change in price.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 Demand计算需求价格弹性,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:如果冰激凌蛋

7、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,Determinants of Price Elasticity of Demand需求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 Time Horizon 时间的长短,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：,例子: 如果冰激凌蛋卷的价格从2.2美元下降到2美元，你的购买量从8个上升到10个，你的需

8、求价格弹性计算如下：,The Midpoint Method: A Better Way to Calculate Percentage Changes and Elasticities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 formula is preferable when calculating the price elasticity of demand because it gives the same answer regardless of the directi

9、on 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 the your elasticity of demand, using the midpoint formula, would be calculated

10、as:,点弹性与弧弹性 定义及两者区别,The Variety of Demand Curves多种需求曲线,Inelastic Demand Quantity demanded does not respond strongly to price changes. Price elasticity of demand is less than one 缺乏弹性的需求 需求量不随着价格变化而强烈变化。 需求价格弹性绝对值小于1。 |ed| 1,Elastic Demand Elasticity is greater than 1富有弹性的需求弹性大于1,Quantity 数量,Price 价格

11、,Inelastic Demand Elasticity is less than 1缺乏弹性的需求弹性小于1,Quantity 数量,Price 价格,The Variety of Demand Curves多种需求曲线,Perfectly Inelastic Quantity demanded does not respond to price changes. 完全无弹性 需求量不随价格变化而变化。 Perfectly Elastic Quantity demanded changes infinitely with any change in price. 完全弹性 价格极小变化引起需

12、求量极大变动。 Unit Elastic Quantity demanded changes by the same percentage as the price. 单位弹性 需求量与价格同比例变动。,Perfectly Inelastic Demand Elasticity equals 0完全无弹性的需求弹性等于0,Quantity 数量,Price 价格,2. .leaves the quantity demanded unchanged. 2.需求量不变。,Unit Elastic Demand Elasticity equals 1单位需求弹性弹性等于1,Quantity 数量,P

13、rice 价格,完全富有弹性弹性等于无穷大,数量,价格,Total Revenue and the Price Elasticity of Demand 总收益与需求价格弹性,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,$4,Demand 需求,Quantity 数量,

14、P,0,Price 价格,P x Q = $400,(total revenue 总收益),100,Total 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.

15、 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总收益如何随着价格变化而变化： 缺乏弹性的需求,$3,Quantity,0,Price,80,Revenue = $240,Demand,$1,Demand,Quantity,0,Revenue = $100,100,Price,An increase in price from $1 to $3.价

16、格从1美元上升到3美元,leads to an increase in total revenue from$100 to $240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 r

17、evenue 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 Demand,Demand,Quantity,0,Price,$4,50,Demand,Quantity,0,Price,Revenue = $100,$5,20,An increase in price from $4 to $5.,leads to a decrease in total revenue from$200 to $100,In

18、come Elasticity of Demand需求的收入弹性,Income 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 percentage change in income. 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

19、除以收入变动的百分比。,Computing Income Elasticity计算收入弹性,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 Inferior 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 -

20、Types of Goods -,Goods consumers regard as necessities tend to be income inelasticExamples include food, clothing, utilities, and medical services. Goods consumers regard as luxuries tend to be income elastic.Examples include sports cars, furs, and expensive foods. 消费者消费的必需品往往收入弹性小 例如：食物、衣服、医疗服务。 消费

21、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,替代品： E0 互补品： E0 无关物品：E0,Price Elasticity of Supply供给的价格弹性,Price 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 th

22、e price of that good. 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。,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。,Determinants of Elasticity of Supply供给弹性的决定因素,Ability of sellers to change the amount of the good they produce.卖者改变它们生产物品产量的能力 Beach-front land is inelastic.海滩前的土地供给是缺乏弹性的。 Icecream are elas

23、tic. 冰激淋供给是富有弹性的。 Time period.时间长短 Supply is more elastic in the long run.供给在长期内更富有弹性,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 agronomi

24、sts 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,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

25、the shift of the curve. 考虑曲线向哪个方向移动。 Use 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 smaller increase in quantity sold. As a result, revenue falls from $300 to $220.,An Increase in Supply in the Market for Wheat,$3,Quantity of Wh

26、eat,100,0,Price of Wheat,1. When demand is inelastic, an increase in supply.,Demand,S1,S2,2,110,2. .leads to a large fall in price.,5,6,$7,4,1,2,3,Quantity 数量,12,2,4,6,8,10,14,0,Price 价格,Figure 5-5,A,B,C,Quantity 数量,0,Price 价格,Figure 5-7,A,Quantity 数量,0,Price 价格,Figure 5-7,A,B,T,R,M,N,$15,12,3,Quant

27、ity 数量,100,200,500,0,Price 价格,525,Elasticity is small,(less than 1).,Elasticity is large,(greater than 1).,4,Figure 5-7,弹性小（1）,弹性大（1）,P2,P1,Quantity of Oil,0,Price of Oil,Demand,S,2,S,1,(a) The Oil Market in the Short Run,P2,P1,Quantity of Oil,0,Price of Oil,Demand,S,2,S,1,(b) The Oil Market in the

28、Long Run,2. .leads,to a large,increase,in price.,1. In the long run,when supply and,demand are elastic,a shift in supply.,2. .leads to a small increase in price.,1. In the short run, when supply,and demand are inelastic,a shift in supply.,Figure 5-9,欧佩克能否保持稳固联盟？,P2,P1,石油数量,0,石油价格,需求,S,2,S,1,(a) 短期石油

29、市场,P2,P1,石油数量,0,石油价格,需求,S,2,S,1,(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 5-9,P,2,P,1,Quantity of Drugs,0,Q,2,Q,1,Price of,Drugs,Demand,S,2,S,1,Q,2,Q,1,(a) Drug Interdiction,Quantity of Drugs,0,Price of,Drugs,Supply,D,2,D,1,(b) Drug Education,3.

30、 .and reduces the,quantity sold.,2. .which,raises the,price.,2. .which,reduces,the price.,P,1,P,2,1. Drug interdiction reduces,the supply of drugs.,1. Drug education reduces,the demand for drugs.,3. .and reduces the,quantity sold.,Figure 5-10,P,2,P,1,毒品数量,0,Q,2,Q,1,毒品价格,需求,S,2,S,1,Q,2,Q,1,(a) 禁毒,毒品数

31、量,0,毒品价格,供给,D,2,D,1,(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,P,1,P,2,1. 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,经济危机首当其冲的是什么行业？,Summary,Price elasticity of demand measures how much the quantity demanded responds to changes in the price. Price elasticity of demand is calculated as the percentage change in quantity demanded divided by the percentage change in price. If a demand curve is elastic, total r