第七版微观经济学-第5章-弹性及其应用

1、弹性及其应用, 2015 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use.,1,需求弹性,弹性 衡量需求量或供给量的反应程度 对其决定因素中的

2、一种变动 需求的价格弹性 衡量一种物品需求量对其价格变动作出反应的程度的指标, 2015 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use.,2

3、,需求弹性,需求的价格弹性 需求量变动的百分比除以价格变动的百分比 富有弹性 需求量对价格的变动作出很大的反应 缺乏弹性 需求量只对价格变动作出很小的反应, 2015 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password

4、-protected website for classroom use.,3,需求弹性,需求价格弹性的决定因素 相近替代品的可获得性 有相近替代品的商品：较富有弹性 必需品与奢侈品 需求：缺乏弹性 奢侈品：富有弹性, 2015 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or ser

5、vice or otherwise on a password-protected website for classroom use.,4,需求弹性,需求价格弹性及其决定因素 市场的定义 狭义的市场：更加富有弹性 时间维度 物品的需求往往在长期内更富有弹性, 2015 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a c

6、ertain product or service or otherwise on a password-protected website for classroom use.,5,需求弹性,计算需求价格弹性 需求量变动百分比除以价格变动百分比 使用绝对值（去掉符号） 中点法 两点: (Q1, P1) 和 (Q2, P2), 2015 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted

7、 in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use.,6,需求弹性,各种需求曲线 需求富有弹性 需求价格弹性 1 缺乏弹性 需求价格弹性 1 单位弹性 需求价格弹性 = 1, 2015 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except

8、for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use.,7,需求弹性,各种需求曲线 需求完全缺乏弹性 需求价格弹性 = 0 需求曲线垂直 需求完全弹性 需求价格弹性 = 无穷 需求曲线水平, 2015 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, i

9、n whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use.,8,图 1,9, 2015 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for u

10、se as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use.,需求价格弹性(a, b),需求价格弹性: e=0,$5,4,1. An increase in price,2. leaves the quantity demanded unchanged,(b) 缺乏弹性: e小于1,$5,4,1. A 22% increase in price,2. leads to an 11%

11、 decrease in quantity demanded,100,90,需求的价格弹性决定了需求曲线是陡峭的还是平坦的。 要注意的是，所有的百分比变动是用中点法计算的。,图 1,10, 2015 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwi

12、se on a password-protected website for classroom use.,需求价格弹性 (c),(c) 单位弹性需求：弹性等于 1,$5,4,1. A 22% increase in price,2. leads to a 22% decrease in quantity demanded,100,80,需求的价格弹性决定了需求曲线是陡峭的还是平坦的。 要注意的是，所有的百分比变动是用中点法计算的。,图 1,11, 2015 Cengage Learning. All Rights Reserved. May not be copied, scanned, o

13、r duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use.,需求价格弹性 (d, e),(d) Elastic demand: Elasticity 1,$5,4,A 22% increase in price,2. leads to a 67% decrease in quantity

14、 demanded,100,50,需求的价格弹性决定了需求曲线是陡峭的还是平坦的。 要注意的是，所有的百分比变动是用中点法计算的。,(e) Perfectly elastic demand: Elasticity equals infinity,1. At any price above $4, quantity demanded is zero,2. At exactly $4, consumers will buy any quantity,3. At a price below $4, quantity demanded is infinite,需求弹性,总收益, TR 一种物品的买者支

15、付从而卖者得到的量 价格乘以销售数量 (P Q) 价格上升时 若需求缺乏弹性, TR 上升 若需求富有弹性, TR 下降, 2015 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected websit

16、e for classroom use.,12,图 2,13, 2015 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use.,总收益,Deman

17、d,Price,买者支付的的从而卖者作为收益得到的总量等于需求曲线下方的方框面积，即PXQ。在这里，价格为4美元，需求量为100，总收益400美元。,100,$4,图 3,14, 2015 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on

18、 a password-protected website for classroom use.,如何总收入变动时，价格变动,and,对总收入的价格变动的影响（价格和数量取决于需求价格弹性）。在（a）幅中，需求曲线是缺乏弹性的。在这种情况下，价格上升引起的需求量减少的比例小于价格上升的比例，因此，总收益是增加的。在这里，价格从4美元增加到5美元，这使得需求量从100下降到90。总收入从400美元上升到450美元。（b）幅，需求曲线富有弹性， 在这种情况下，价格上升引起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。5美元减低到4美元，这使得需求量从100下降到70。总收入从400美

19、元减少为350美元。,2. . . . the extra revenue from selling at a higher price . . .,需求弹性,缺乏弹性（当需求弹性小于1） P和TR在同一方向移动 若P , TR 也 当富有弹性（弹性是大于1） P和TR在相反的方向移动 若 P , TR 如果需求是单位弹性（弹性= 1） 总收入保持不变时，价格变动, 2015 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except

20、for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use.,15,需求弹性,线性需求曲线 斜率不变 不同的价格弹性 在价格低和数量高的各点上 缺乏弹性 在价格高和数量低的各点上 富有弹性, 2015 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in w

21、hole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use.,16,图 4,17, 2015 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for us

22、e as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use.,线性需求曲线的弹性,1. an,Price,6,5,4,3,2,1,2,4,6,8,10,12,线性需求曲线的斜率是不变的，但它的弹性并不是不变的。表中的需求表是用中点法来计算需求价格弹性的。在低的价格和高的数量，需求曲线是缺乏弹性的。以高价格和低的价格点，需求曲线是富有弹性的。,图 4,18, 2015 Cengage

23、Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use.,线性需求曲线的弹性,线性需求曲线的斜率是不变的，但它的弹性并不是不变的。表中的需求表是用中点法来计算需求价格

24、弹性的。在低的价格和高的数量，需求曲线是缺乏弹性的。以高价格和低的价格点，需求曲线是富有弹性的。,需求弹性,需求的收入弹性 衡量一种物品需求量对消费者收入变动反应程度的指标 用需求量变动百分比 除以收入的变动百分比, 2015 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or serv

25、ice or otherwise on a password-protected website for classroom use.,19,需求弹性,正常品 单位收入弹性 必需品 单位收入弹性 奢侈品 较大的收入弹性 低档品 负的单位收入弹性, 2015 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain

26、product or service or otherwise on a password-protected website for classroom use.,20,需求弹性,需求的交叉价格弹性 衡量一种物品的需求量对另一种物品价格的变动作出反应程度 第一种物品需求量的变动百分比除以第二种物品价格的变动百分比, 2015 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a

27、 license distributed with a certain product or service or otherwise on a password-protected website for classroom use.,21,需求弹性,替代品 可以替代的物品通常作为一种用途 正的的交叉价格弹性 互补品 通常一起使用的物品 负的交叉价格弹性, 2015 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for

28、use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use.,22,供给弹性,供给价格弹性 供给量变动百分比 一种物品的供给量对另一种物品价格的变动作出反应程度 除以价格变动的百分比 取决于卖者改变他们生产量的灵活性, 2015 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplic

29、ated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use.,23,供给弹性,供给富有弹性 供给量对价格的变动作出很大反应 供给缺乏弹性 供给量只对价格的变动作出微小反应 供给价格弹性的决定因素 时间期限 长期中，更富有弹性, 2015 Cengage Learning. All Rights Reser

30、ved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use.,24,供给弹性,计算供给价格弹性 供给量变动百分比除以价格变动百分比 总是正的 中点法 两点: (Q1, P1) 和 (Q2, P2), 2015 Cengag

31、e Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use.,25,供给弹性,各种供给曲线 供给是单位弹性 供给价格弹性= 1 供给富有弹性 供给价格弹性1 供给缺乏

32、弹性 供给价格弹性1, 2015 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use.,26,供给弹性,各种供给曲线 供给是完全缺乏弹性的 供给的

33、价格弹性 = 0 供给曲线是一条垂直线 供给是富有弹性的 供给的价格弹性 = 无穷 供给曲线是水平的, 2015 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for clas

34、sroom use.,27,图 5,28, 2015 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use.,供给的价格弹性 (a, b),(a)

35、Perfectly Inelastic Supply: Elasticity Equals 0,$5,4,1. An increase in price,2. leaves the quantity supplied unchanged,(b) Inelastic Supply: Elasticity Is Less Than 1,$5,4,100,110,供给的价格弹性决定了供给曲线是陡峭的还是平坦的。 要注意的是，所有的百分比变动是用中点法计算的。,Supply,图 5,29, 2015 Cengage Learning. All Rights Reserved. May not be c

36、opied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use.,供给的价格弹性 (c),(c) Unit Elastic Supply: Elasticity Equals 1,$5,4,100,125,供给的价格弹性决定了供给曲线是陡峭的还是平坦的。 要注

37、意的是，所有的百分比变动是用中点法计算的。,Supply,供给弹性,供给曲线 不同的价格弹性 低价格和低数量的点 富有弹性 没有使用的生产能力 高价格和高数量的点 缺乏弹性, 2015 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a

38、 password-protected website for classroom use.,30,图 6,31, 2015 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website fo

39、r classroom use.,供给的价格弹性怎么变动,$15,12,100,525,因为企业的生产能力通常有一个最大值，所以，在低水平的供给量，供给弹性非常高。在高水平的供给量，供给弹性又会非常低。在这里，的价格从3美元上升到4美元，供给量从100增加到200。由于供给量增加了67%（使用中点法计算）是大于价格上涨的比例29%，所以，供给曲线是富有弹性的。与此相反，当价格从12美元上升到15美元时，供给量仅从500增加到525。由于供给量的5%的增长幅度小于22%的价格，所以，在这个范围内供给曲线是缺乏弹性的。,500,200,4,3,应用,农业的好消息可能对农民来说是坏消息吗？ 小麦新杂

40、交-增产20% 供给曲线向右移动 数量越大，价格越低 需求是缺乏弹性的：总收入下降, 2015 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use

41、.,32,图 7,33, 2015 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use.,小麦市场供给增加,S1,S2,农业技术的进步使小麦供给从

42、S1增加到S2，小麦价格下降。因为对小麦的需求是缺乏弹性的，销售数量从100到110的增加比例小于价格从3美元到2美元的下降比例。结果，农民的总收入是从300美元（3美元X100美元）下降到220美元（2美元X110美元）。,Price of Wheat,110,$3,2,100,Demand,应用,农业的好消息可能对农民来说是坏消息吗？ 公共政策悖论 诱导农民不种植作物, 2015 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, exc

43、ept for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use.,34,应用,为什么石油输出国组织不能保持石油的高价格？ 在1973-1974年提高价格，1971-1981年翻一番 短期运行：供给和需求是缺乏弹性的 减少供给：价格大幅增加 -长期运行：供给和需求是富有弹性的 供给减少：价格小幅上升, 2015 Cengage Learning. All Rights

44、Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use.,35,图 8,36, 2015 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a passw