弹性及其应用 弹性 Elasticity Elasticity and Its ◆…是买者和卖者对市场环境变化作出反应的 Application 程度大小的一种度量方法 is a measure of how much buvers and sellers respond to changes in market conditions 第5章 Chapter 5 ◆…使我们能够更精确地分析供给和需求 llows us to analyze supply and demand with greater precision 需求的价格弹性 需求价格弹性的决定因素 Determinants of Price Elasticity of Demand Price Elasticity of Demand 给定百分之一的价格变化,需求量变化的百分 ◆必品还是膏修品 Necessities versus luxuries Price elasticity of demand is the percentage change in quantity demanded given a percent ◆相近普代品的可获得性 change in the price Availability of Close Substitut 杨扬的界定 ◆它衡量了一种物品的需求量对该物品价格变化 Definition ofthe Mark 出反应的程度大小 时闻范 It is a measure of how much the quantity Time Horizon demanded of a good responds to a change in the price of that good. 需求价格弹性的决定因素 计算需求价格弹性 Determinants of Computing the Price Elasticity Price Elasticity of Demand of demand 那求倾向于更富有弹性 用需求量变动的百分数除以价格变动的百分数 Demand tends to be more elastic 就计算出了需求的价格弹性 ◆如果该商品是奢侈品 The price elasticity of demand is computed as the percentage change in the quantity demanded ◆时间间隔越长 divided by the percentage change in price. Pe巨分数ge ◆相近替代品的个数越多 Price Elasticity of Demand= Quantity Demanded the larger the number of close substitutes. 需求价格弹性 Percentage Change ◆市场界定得越狭隘 价格变化的百分数 the more narrowly defined the market
1 弹性及其应用 Elasticity and Its Application 第5章 Chapter 5 弹性 Elasticity . . . ……是买者和卖者对市场环境变化作出反应的 程度大小的一种度量方法 … is a measure of how much buyers and sellers respond to changes in market conditions ……使我们能够更精确地分析供给和需求 … allows us to analyze supply and demand with greater precision. 需求的价格弹性 Price Elasticity of Demand 给定百分之一的价格变化，需求量变化的百分 数就是需求的价格弹性。 Price elasticity of demand is the percentage change in quantity demanded given a percent change in the price. 它衡量了一种物品的需求量对该物品价格变化 作出反应的程度大小。 It is a measure of how much the quantity demanded of a good responds to a change in the price of that good. 需求价格弹性的决定因素 Determinants of Price Elasticity of Demand 必需品还是奢侈品 Necessities versus Luxuries 相近替代品的可获得性 Availability of Close Substitutes 市场的界定 Definition of the Market 时间范围 Time Horizon 需求价格弹性的决定因素 Determinants of Price Elasticity of Demand 需求倾向于更富有弹性： Demand tends to be more elastic : 如果该商品是奢侈品 if the good is a luxury. 时间间隔越长 the longer the time period. 相近替代品的个数越多 the larger the number of close substitutes. 市场界定得越狭隘 the more narrowly defined the market. 计算需求价格弹性 Computing the Price Elasticity of Demand 用需求量变动的百分数除以价格变动的百分数， 就计算出了需求的价格弹性 The price elasticity of demand is computed as the percentage change in the quantity demanded divided by the percentage change in price. 需求价格弹性 Price Elasticity of Demand = Percentage Change in Quantity Demanded Percentage Change in Price Price Elasticity of Demand = Percentage Change in Quantity Demanded Percentage Change in Price 需求量变化的百分数 价格变化的百分数
计算需求价格弹性 运用中点公式计算需求价格弹性 Computing the Price Elasticity computing the Price Elasticity of Demand Using the Midpoint of demand Formula Percentage change in quatity demanded ◆如果你试图计算需求曲线上两点之 格弹性,你马上就会注意到一个恼 如果冰演淋蛋卷的价格从20美元上升到220美元,你所购买 从A点到B点的弹性,与从B点到A点 量从10个下障到8个,那么你的需求弹性可以计算如下: 不同的。 ao plei: the he prict of a bie e reases from S2. 00 to t you buy falls from 10 to 8 cones then your If you try calculate the price elasticity of elasticity of demand would he caleulated as demand between two points on a demand curve, you will quickly notice an annoying -20 percent problem: The elasticity from point A to point B seems different from the elasticity from point B 2.20-20×10010 percent 运用中点公式计算需求价格弹性 运用中点公式计算需求价格弹性 Computing the Price Elasticity of Computing the Price Elasticity of Demand Using the Midpoint Demand Using the Midpoint Formula Formula ◆例如,考虑下面的数字 For example, consider these numbers 当计算需求价格弹性时,中点公式更为可取,因 e Point A: Price=S4, Quantity=120 为无论变化的方向如何,它都能给出相同的答案 e Point B: Price=S6 Quantity=80 The midpoint formula is preferable when ◆弹性分别是 Elasticities are, calculating the price elasticity of demand because it gives the same answer regardless of the direction of ◆I(80-120)/120(6-4)/4|=(-33).5=-0.66 Price Elasticity of Demand=(Q-Q,)/(Q+Q)/2)1 ◆B→A: (P2-P1)/[(P2+P1)2] ◆l(120-8080/1(46)/6=5/(-33)=1.5 运用中点公式计算需求价格弹性 computing the Price Elasticity of 计算需求价格弹性 Demand Using the Midpoint Computing the Price Elasticity Formula of demand ◆在我们的例子中,A点和B点的中点是 Price Elasticity of Demand =(Qx-Qn/(Q 2+Q1/21 In our example, the mid point between point A 2-P1)[(P2+P1)2 and B is ◆中点 Midpoint:价格 Prices=S5,数量 Quantity=100 量从10个下降到个,运用中点公式,你的求弹性就可以计算如下 ◆无论方向,弹性均为1 S2.20 and the amount you buy falls from 10 to 8 cones, then your .A- in both directions equals I Elas elasticity of demand, using the midpoint formula, would be calculated ◆(80-120/100y(6-4)5=(-.2).2=1 (10+8)/2 ◆B→A: 22 percent=2.32 ◆(120-80/100(4-6)5}=,2/(-2)=1 (2.00+2.20)/2
2 计算需求价格弹性 Computing the Price Elasticity of Demand Percentage change in price Percentage change in quatity demanded Price elasticity of demand = 例：如果冰淇淋蛋卷的价格从2.00美元上升到2.20美元，你所购买 的数量从10个下降到8个，那么你的需求弹性可以计算如下： 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: (8 10) 100 10 20 2 (2.20 2.00) 10 100 2.00 percent percent − × − = =− − × 运用中点公式计算需求价格弹性 Computing the Price Elasticity of Demand Using the Midpoint Formula 如果你试图计算需求曲线上两点之间的需求价 格弹性，你马上就会注意到一个恼人的问题： 从A点到B点的弹性，与从B点到A点的弹性是 不同的。 If you try calculate the price elasticity of demand between two points on a demand curve, you will quickly notice an annoying problem: The elasticity from point A to point B seems different from the elasticity from point B to point A. 运用中点公式计算需求价格弹性 Computing the Price Elasticity of Demand Using the Midpoint Formula 例如，考虑下面的数字 For example, consider these numbers: Point A: Price=$4, Quantity=120 Point B: Price=$6, Quantity=80 弹性分别是 Elasticities are, A→B: [(80-120)/120]/[(6-4)/4] =(-.33)/.5=-0.66 B →A: [(120-80)/80]/[(4-6)/6]=.5/(-.33)=-1.5 运用中点公式计算需求价格弹性 Computing the Price Elasticity of Demand Using the Midpoint Formula 当计算需求价格弹性时，中点公式更为可取，因 为无论变化的方向如何，它都能给出相同的答案 The midpoint formula is preferable when calculating the price elasticity of demand because it gives the same answer regardless of the direction of the change. (P P )/[(P P )/2] (Q Q )/[(Q Q )/2] Price Elasticity of Demand= 2 1 2 1 2 1 2 1 − + − + 运用中点公式计算需求价格弹性 Computing the Price Elasticity of Demand Using the Midpoint Formula 在我们的例子中，A点和B点的中点是 In our example, the midpoint between point A and B is, 中点Midpoint:价格Price=$5, 数量Quantity=100. 无论方向，弹性均为1 Elasticity in both directions equals 1, A→B: [(80-120)/100]/[(6-4)/5] =(-.2)/.2=-1 B →A: [(120-80)/100]/[(4-6)/5]=.2/(-.2)=-1 计算需求价格弹性 Computing the Price Elasticity of Demand 例：如果冰淇淋蛋卷的价格从2.00美元上升到2.20美元，而你购买的数 量从10个下降到8个，运用中点公式，你的需求弹性就可以计算如下： 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, using the midpoint formula, would be calculated as: 2.32 9.5 22 (2.00 2.20)/ 2 (2.20 2.00) (10 8)/ 2 (10 8) = = + − + − percent percent (P P )/[(P P )/2] (Q Q )/[(Q Q )/2] Price Elasticity of Demand = 2 1 2 1 2 1 2 1 − + − +
弹性的范围 计算需求价格弹性 Ranges of Elasticity Computing the Price Elasticity 峡乏弹性的求 Inelastic demand of demand ◆需求量的变化对价格变化的反应不强烈 Price Quantity demanded does not respond strongly to price (10050)/2 4.00-5.00Z ◆需求价格弹性小于1 (4.00+500/2 Price elasticity of demand is less than on 富于弹性的需求 Elastic demand 67 percent=-3 ◆需求量的变化对价格的变化反应强烈 Quantity demanded responds strongly to changes in 求是富干价格弹性的 ◆需求价格弹性大 0 50 100 Quantity Demand is price elastic Price elasticity of demand is greater than one. 弹性的范围 需求曲线的变化 Ranges of Elasticity A Variety of Demand Curves ◆完全无苹性 Perfectly Inelastic 需求量对价格变化不作出反应 ◆因为需求价格弹性衡量了需求量对价格 nded does not respond to price changes. 的反应程度,它就和需求曲线的斜率密 ◆完全(有)弹性 Perfectly Elastic 切相关。 对价格的任何变化,需求量的变化无穷大 Because the price elasticity of demand measures how much quantity demanded ◆单位弹性 Unit Elasti responds to the price, it is closely related 需求量变化和价格变化的百分数相同 to the slope of the demand curve. Quantity demanded changes by the same percentage as the price. ◆通过某一点的需求曲线越平坦,需求的 价格弹性就越大。 完全无弹性的需求:弹性为零 缺乏弹性的需求:弹性小于1 Perfectly Inelastic Demand Inelastic Demand Elasticity equals 0 Elasticity is less than 1 教量 Quantity 2.没有引起需求量的任何变化 2..导致需求量下降11% leads to a 11 decrease in quantity
3 弹性的范围 Ranges of Elasticity 缺乏弹性的需求 Inelastic Demand 需求量的变化对价格变化的反应不强烈 Quantity demanded does not respond strongly to price changes. 需求价格弹性小于1 Price elasticity of demand is less than one. 富于弹性的需求 Elastic Demand 需求量的变化对价格的变化反应强烈 Quantity demanded responds strongly to changes in price. 需求价格弹性大于1 Price elasticity of demand is greater than one. 计算需求价格弹性 Computing the Price Elasticity of Demand 需求是富于价格弹性的 Demand is price elastic $5 4 Demand 0 100 Quantity Price 50 -3 -22percent 67percent (4.00 5.00)/2 (4.00-5.00) (100 50)/2 (100-50) ED = = + + = 弹性的范围 Ranges of Elasticity 完全无弹性 Perfectly Inelastic 需求量对价格变化不作出反应 Quantity demanded does not respond to price changes. 完全（有）弹性 Perfectly Elastic 对价格的任何变化，需求量的变化无穷大 Quantity demanded changes infinitely with any change in price. 单位弹性 Unit Elastic 需求量变化和价格变化的百分数相同 Quantity demanded changes by the same percentage as the price. 需求曲线的变化 A Variety of Demand Curves 因为需求价格弹性衡量了需求量对价格 的反应程度，它就和需求曲线的斜率密 切相关。 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. 通过某一点的需求曲线越平坦，需求的 价格弹性就越大。 完全无弹性的需求：弹性为零 Perfectly Inelastic Demand - Elasticity equals 0 数量 Quantity 价格 Price 4 $5 需求 Demand 100 2. …没有引起需求量的任何变化 leaves the quantity demanded unchanged. 1. 价格 上升 An increase in price... 缺乏弹性的需求：弹性小于1 Inelastic Demand - Elasticity is less than 1 数量 Quantity 价格 Price 4 1.价格 $5 上升22％ A 22% increase in price... 需求 Demand 90 100 2. …导致需求量下降11％ leads to a 11% decrease in quantity
单位弹性的需求:弹性等于1 富于弹性的需求:弹性大于1 Unit Elastic Demand Elastic Demand Elasticity equals 1 Elasticity is greater than 1 价格 量 Quantity 量 Quantity 2.导致需求 2.导致求量下降67% leads to a 67% decrease in quantity 完全弹性的需求:弹性无穷大 美国经济中部分物品的弹性 Perfectly Elastic Demand Some Price Elasticities in the Elasticity equals infinity U.S. Economy Price 富于弹性的需求 Elastie demands 7在外就餐 Purchased meals 2.27 7金属 Metals 1.52 7木制家具 Furnitures, timber 求 Demand 刁汽车 Motor vehicles 运输 Transportation 着管产天向爱量 m缺乏弹性的需求 Inelastic demands buy any quantity 石油Oil 3在价低于元时,求量为无射大 7化学药品 Chemicals quantity demanded is infinite. 美国经济中部分物品的弹性 Some price elasticities in the 弹性与总收益 U.S. Economy Elasticity and Total Revenue 缺乏弹性的需求 Inelastic demands( contd.) ◆总收益是一个物品的买者支付的金额, 饮料Be 也是其卖者收取的金额 烟草 Tobacco Total revenue is the amount paid by buyers and received by sellers of a good. 7住宅服务 Housing service ◆用该物品的价格乘以出售量来计算 7衣服 Clothing .49 Computed as the price of the good times 7书报杂志 Books,, Magazines,. newspapers.34 the quantity sold TR=PX Q
4 单位弹性的需求：弹性等于1 Unit Elastic Demand - Elasticity equals 1 数量 Quantity 价格 Price 4 1. 价格 $5 上升22％ A 22% increase in price... 需求 Demand 80 100 2. …导致需求量下降22％ leads to a 22% decrease in quantity. 富于弹性的需求：弹性大于1 Elastic Demand - Elasticity is greater than 1 数量 Quantity 价格 Price 4 $5 1. 价格 上升22％ A 22% increase in price... 需求 Demand 50 100 2. …导致需求量下降67％ leads to a 67% decrease in quantity. 完全弹性的需求：弹性无穷大 Perfectly Elastic Demand - Elasticity equals infinity 数量 Quantity 价格 Price 需求 Demand $4 1. 在4美元以上的任何 价格，需求量都为零 At any price above $4, quantity demanded is zero. 2. 价格恰为4美元时， 消费者愿意购买任何数量 At exactly $4, consumers will buy any quantity. 3. 在价格低于4美元时，需求量为无穷大 At a price below $4, quantity demanded is infinite. 美国经济中部分物品的弹性 Some Price Elasticities in the U.S. Economy 富于弹性的需求 Elastic demands Ê在外就餐 Purchased meals 2.27 Ê金属 Metals 1.52 Ê木制家具 Furnitures, timber 1.25 Ê汽车 Motor Vehicles 1.14 Ê运输 Transportation 1.03 缺乏弹性的需求 Inelastic demands Ê水电气 Gas, electricity, water .92 Ê石油 Oil .91 Ê化学药品 Chemicals .89 美国经济中部分物品的弹性 Some Price Elasticities in the U.S. Economy 缺乏弹性的需求 Inelastic demands (contd.) Ê饮料 Beverages .78 Ê烟草 Tobacco .61 Ê食物 Food .58 Ê住宅服务 Housing service .55 Ê衣服 Clothing .49 Ê书报杂志 Books, magazines, newspapers .34 Ê肉类 Meat .2 Sources: Ahson Mansur and John Whalley, “Numerical Specification of Applied General Equilibrium Models: Estimation, Calibration, and Data”, in Scarf and Shoven, eds., Applied General Equilibrium Analysis (New York: Cambridge University Press,1984), p. 109; Hendrik S. Houthakker and Lester D. Taylor, Consumer Demand in the United States: Analysis and Projections (Cambridge: Harvard University Press, 1970). 弹性与总收益 Elasticity and Total Revenue 总收益是一个物品的买者支付的金额， 也是其卖者收取的金额。 Total revenue is the amount paid by buyers and received by sellers of a good. 用该物品的价格乘以出售量来计算。 Computed as the price of the good times the quantity sold. TR = P x Q
弹性与总收益 弹性与总收益 Elasticity and Total Revenue Elasticity and Total Revenue 对于缺乏弹性的需求曲线,当价格 上升时,需求量下降的比例小于价 格上升的比例。从而总收益上升 PxQ=5400 With an inelastic demand curve, 总收益 total revenue 需求 Demand increase in price leads to a decrease in quantity that is proportionately smaller. Thus total revenue Increases 弹性与总收益:缺乏弹性的需求 Elasticity and Total Revenue 弹性与总收益 Inelastic Demand Elasticity and Total Revenue 价格 对于富于弹性的需求曲线,当价格 价格从S1上升到 到S240美元 上升时,需求量下降的比例大于价 SI to S3 格上升的比例。从而总收益下降 With an elastic demand curve. an increase in the price leads to a decrease in quantity demanded that 需求 is proportionately larger. Thus, total revenue decreases 弹性与总收益:富于弹性的需求 Elasticity and Total revenue 案例研究:旅游景点门票定价 Elastic Demand 导敦总收益从5200下降 ◆如果你是颐和园的负责人,你的财务经 从4上升到 理告诉你,由于资金缺乏,无法进行正 常的景观维护,建议你考虑改变门票价 以增加总收益。你将提高还是降低门 票价格? 求 Demand t Reven Revenue=5100 ◆如果你是北京市一家电影院的经理,同 样的情况下,你的考虑又如何?
5 $4 需求 Demand 数量 Quantity P 0 价格 Price P x Q = $400 (总收益total revenue) 100 Q 弹性与总收益 Elasticity and Total Revenue 弹性与总收益 Elasticity and Total Revenue 对于缺乏弹性的需求曲线，当价格 上升时，需求量下降的比例小于价 格上升的比例。从而总收益上升。 With an inelastic demand curve, an increase in price leads to a decrease in quantity that is proportionately smaller. Thus, total revenue increases. 弹性与总收益：缺乏弹性的需求 Elasticity and Total Revenue: Inelastic Demand $3 数量 Quantity 0 价格 Price 80 Revenue = $240 需求 Demand $1 需求 Demand 数量 Quantity 0 收益Revenue = $100 100 价格 Price 价格从$1上升到$3 An increase in price from $1 to $3... …引起总收益从$100增加 到$240美元 leads to an increase in total revenue from$100 to $240 弹性与总收益 Elasticity and Total Revenue 对于富于弹性的需求曲线，当价格 上升时，需求量下降的比例大于价 格上升的比例。从而总收益下降。 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. 弹性与总收益：富于弹性的需求 Elasticity and Total Revenue: Elastic Demand 需求Demand 0 数量 Quantity 价格 Price $4 50 需求Demand 0 数量 Quantity Price Revenue = $100 $5 20 收益Revenue = $200 价格从$4上升到$5 An increase in price from $4 to $5... …导致总收益从$200下降 到$100 leads to a decrease in total revenue from$200 to $100 案例研究：旅游景点门票定价 如果你是颐和园的负责人，你的财务经 理告诉你，由于资金缺乏，无法进行正 常的景观维护，建议你考虑改变门票价 格以增加总收益。你将提高还是降低门 票价格？ 如果你是北京市一家电影院的经理，同 样的情况下，你的考虑又如何？
计算线性需求曲线的弹性 Computing the Elasticity of a 需求的收入弹性 Linear Demand curve Income Elasticity of Demand 鉴心滑使衡度大品的需求量对消者 asticity of demand much the quantity demanded of a good responds to a change in consumers'income. ◆用需求量变化的百分数除以收入变化的百分数 It is computed as the percentage change in the quantity demanded divided by the percentage ige in incom 计算收入弹性 收入弹性:物品的类型 Computing Income Elasticity Income Elasticity Types of Goods Percentage Cha ◆正信品 Normal good Income Elasticity ◆劣等品 Inferior Goods ercentage Change 对于正常品来说,更高的收入增加了对 它的需求量;对于劣等品来说,更高的 求的收入弹性= 收入少了对它的需求量 需求量变化的百分数收入变化的百分数 Higher income raises the quantity demanded for normal goods but lowers the quantity demanded for inferior 收入弹性:物品的类型 Income Elasticity 收入弹性的应用 Types of Goods 某物品被消贵看作必需品,它款钡向于黄王收入 ◆随着一国的经济增长和人们收入水平提高,哪 regard as necessities tend to b 种物品的支出额在收入中的比重增加,必需品 income inelastic 还是奢侈品? ●例如食物、常油、衣服、公用事业、图疗服务 Examples include food, fuel clothing, utilities, and medical ◆看侈品 ◆例子:中国,奢侈品成为消费“热点 ◆某些物品被消费者看作奢侈品,它就倾向于喜于此入 ◆80年代:“三大件”—电视、冰箱、洗衣机 oods consumers regard as luxuries tend to be income ◆90年代:空调、汽车、电脑 elastic 例如跑车、毛皮衣服、高档食品 ◆现在:住房、旅游 Examples include sports cars, furs, and expensive foods
6 计算线性需求曲线的弹性 Computing the Elasticity of a Linear Demand Curve Price Quantity Total Revenue (Price x Quantity) Percent Change in Price Percent Change in Quantity Elasticity Description $0 14 $0 200% 15% 0.1 Inelastic 1 12 12 67 18 0.3 Inelastic 2 10 20 40 22 0.6 Inelastic 3 8 24 29 29 1 Unit elastic 4 6 24 22 40 1.8 elastic 5 4 20 18 67 3.7 elastic 6 2 12 15 200 13 elastic 7 0 0 需求的收入弹性 Income Elasticity of Demand 需求收入弹性衡量一个物品的需求量对消费者 收入变化的反应程度大小。 Income elasticity of demand measures how much the quantity demanded of a good responds to a change in consumers’ income. 用需求量变化的百分数除以收入变化的百分数 来计算。 It is computed as the percentage change in the quantity demanded divided by the percentage change in income. 计算收入弹性 Computing Income Elasticity Income Elasticity of Demand Percentage Change in Quantity Demanded Percentage Change in Income = 需求的收入弹性＝ 需求量变化的百分数/收入变化的百分数 收入弹性：物品的类型 Income Elasticity - Types of Goods - 正常品 Normal Goods 劣等品 Inferior Goods 对于正常品来说，更高的收入增加了对 它的需求量；对于劣等品来说，更高的 收入减少了对它的需求量 Higher income raises the quantity demanded for normal goods but lowers the quantity demanded for inferior goods. 收入弹性：物品的类型 Income Elasticity - Types of Goods - 某些物品被消费者看作必需品，它就倾向于缺乏收入 弹性 Goods consumers regard as necessities tend to be income inelastic 例如食物、燃油、衣服、公用事业、医疗服务 Examples include food, fuel, clothing, utilities, and medical services. 某些物品被消费者看作奢侈品，它就倾向于富于收入 弹性 Goods consumers regard as luxuries tend to be income elastic. 例如跑车、毛皮衣服、高档食品 Examples include sports cars, furs, and expensive foods. 收入弹性的应用 随着一国的经济增长和人们收入水平提高，哪 种物品的支出额在收入中的比重增加，必需品 还是奢侈品？ 奢侈品！ 例子：中国，奢侈品成为消费“热点” 80年代：“三大件”——电视、冰箱、洗衣机 90年代：空调、汽车、电脑 现在：住房、旅游
中国:城镇居民消费支出构成 供给的价格弹性 Price Elasticity of Supply 耸的化格普棼最价格变化百分之一导致的供 Price elasticity of supply is the percentage 家设备用品及服务 c hange in quantity supplied resulting from 医打保健 percent change in price. 交還還讯 乐教育文化服务 反应的度关小翕种独是效价格变化作出 素量 It is a measure of how much the quantity supplied of a good responds to a change in the 来国年 price of that good 弹性的范围 弹性的范围 Ranges of Elasticity Ranges of Elasticity 完全弹性 Perfectly Elastic ◆较缺乏弹性 Relatively Inelastic E= ao E。1 Es=0 ◆单位弹性 Unit elastic Es=1 完全无弹性的供给:弹性为零 缺乏弹性的供给:弹性小于1 Perfectly Inelastic Supply Inelastic Supply Elasticity equals 0 Elasticity is less thai 1.价格55 线 教量 Quantity 2没有引起供给量的改变 2..导致供给量上升10% leads to a 10% increase in quanti
7 中国：城镇居民消费支出构成 资料来源：《中国统计年鉴》 1992 2003 食品 52.9 37.1 衣着 14.1 9.8 家庭设备用品及服务 8.4 6.3 医疗保健 2.5 7.3 交通通讯 2.6 11.1 娱乐教育文化服务 8.8 14.4 居住 6.0 10.7 杂项商品 4.7 3.3 合计 100.0 100.0 类别 年份 供给的价格弹性 Price Elasticity of Supply 供给的价格弹性是价格变化百分之一导致的供 给量变化的百分数 Price elasticity of supply is the percentage change in quantity supplied resulting from a percent change in price. 它是对物品的供给量对该物品的价格变化作出 反应的程度大小的一种度量方法 It is a measure of how much the quantity supplied of a good responds to a change in the price of that good. 弹性的范围 Ranges of Elasticity 完全弹性 Perfectly Elastic ES = ∞ 较富于弹性 Relatively Elastic ES > 1 单位弹性 Unit Elastic ES = 1 弹性的范围 Ranges of Elasticity 较缺乏弹性 Relatively Inelastic ES < 1 完全无弹性 Perfectly Inelastic ES = 0 完全无弹性的供给：弹性为零 Perfectly Inelastic Supply - Elasticity equals 0 数量 Quantity 价格 Price 4 $5 供给 Supply 100 2. …没有引起供给量的改变 leaves the quantity supplied unchanged. 1. 价格 上升 An increase in price... 缺乏弹性的供给：弹性小于1 Inelastic Supply - Elasticity is less than 1 数量 Quantity 价格 Price 4 1. 价格 $5 上升22％ A 22% increase in price... 100 110 供给 Supply 2. …导致供给量上升10％ leads to a 10% increase in quantity
单位弹性的供给:弹性等于1 富于弹性的供给:弹性大于1 Unit Elastic Supply Elastic Supply Elasticity equals 1 Elasticity is greater than 1 价格 供给 Supply 供给 Supply 数 qUantity 200量 Quantity 2.致供给量上升22% leads to a 22% increase in quantity. leads to a 67 increase in quantity. 完全弹性的供给:弹性无穷大 供给弹性的决定因素 Perfectly Elastic Supply Determinants of Elasticity equals infinity Elasticity of Supply ◆卖者改变其生产物品的数量的能力 1.只要价格高于4,供给量无穷大 Ability of sellers to change the amount of the good they produce. supplied is infinite. ◆海滩边的士地是无弹性的 供给 Supply Beach-front land is inelastic ●书箭、汽车或者制成品是富于弹性的 2价格恰好为4,生产者属意供给任散量 ks, cars, or mar ◆时间间隔 Time period apply any quantity ◆在长期,供给更有弹性 elastic in the long ru 3价格低于4,供给量为零 quantity supplied is zero. 计算供给价格弹性 Computing the Price Elasticity 弹性的应用 f Supply Application of Elasticity 用快数量的桌子类给龄价格的白分 ●农事的好消息会不会是农民的坏消息? The price elasticity of supply is computed as Can good news for farming be bad news for farmers the percentage change in the quantity ◆当大学里的农学家们发现了一个比现有品种更高产的新 applied divided by the percentage change in 小变杂交品种时,小麦种植者和小麦市场上会发生什么? What happens to wheat farmers and the market for wheat 供给量变化的百分歌 n that is more productive than existing varieties? Elasticity of supply 供给价格弹性 Percentage Change
8 单位弹性的供给：弹性等于1 Unit Elastic Supply - Elasticity equals 1 数量 Quantity 价格 Price 4 1. 价格 $5 上升22％ A 22% increase in price... 100 125 供给 Supply 2. …导致供给量上升22％ leads to a 22% increase in quantity. 富于弹性的供给：弹性大于1 Elastic Supply - Elasticity is greater than 1 数量 Quantity 价格 Price 4 1. 价格 $5 上升22％ A 22% increase in price... 100 200 供给 Supply 2. …导致供给量上升67％ leads to a 67% increase in quantity. 完全弹性的供给：弹性无穷大 Perfectly Elastic Supply - Elasticity equals infinity 数量 Quantity 价格 Price 供给 Supply $4 1. 只要价格高于$4，供给量无穷大 At any price above $4, quantity supplied is infinite. 2. 价格恰好为$4，生产者愿意供给任一数量 At exactly $4, producers will supply any quantity. 3. 价格低于$4，供给量为零 At a price below $4, quantity supplied is zero. 供给弹性的决定因素 Determinants of Elasticity of Supply 卖者改变其生产物品的数量的能力 Ability of sellers to change the amount of the good they produce. 海滩边的土地是无弹性的 Beach-front land is inelastic. 书籍、汽车或者制成品是富于弹性的 Books, cars, or manufactured goods are elastic. 时间间隔 Time period. 在长期，供给更有弹性 Supply is more elastic in the long run. 计算供给价格弹性 Computing the Price Elasticity of Supply 用供给量变化的百分数除以价格变化的百分 数，就算出来了供给的价格弹性。 The price elasticity of supply is computed as the percentage change in the quantity supplied divided by the percentage change in price. Elasticity of Supply = Percentage Change in Quantity Supplied Percentage Change in Price Elasticity of Supply = Percentage Change in Quantity Supplied 供给价格弹性 Percentage Change 供给量变化的百分数 价格变化的百分数 弹性的应用 Application of Elasticity 农事的好消息会不会是农民的坏消息？ Can good news for farming be bad news for farmers? 当大学里的农学家们发现了一个比现有品种更高产的新 小麦杂交品种时，小麦种植者和小麦市场上会发生什么？ What happens to wheat farmers and the market for wheat when university agronomists discover a new wheat hybrid that is more productive than existing varieties?
弹性的应用 小麦市场上供给增加 Application of Elasticity An Increase in Supply in the 小变的价格 Market for Wheat ◆考察是供给还是需求曲线移动 Examine whether the supply or demand curve shifts ◆确定曲线移动的方向。 Determine the direction of the shift of the curve ◆用供求图说明市场均衡如何变化 Use the supply-and-demand diagram to see 求 Demand how the market equilibrium changes. 小麦的量 小麦市场上供给增加 An Increase in Supply in the 计算弹性 arket for wheat Compute Elasticity Price of 乏弹性时,供哈增加 100-110 (100+110/2 3.00-2.00 (300+200/2 0.095 求 Demand -0.24 小的量 04 计算弹性 政策含义 Compute Elasticit Policy Implications 100-110 100+110)/2 “产衣始术民数度减步有套 300-200 (300+200/2 ◆1948年美国有17%人口为农民 1993年仅有2%。但农业产量为原 来的2倍多。 0.095 ≈-024 ◆1952年中国84%劳动力在农业 04 1999年为50%。农业 加了3 倍 求是缺乏弹性的 Demand is inelastic
9 弹性的应用 Application of Elasticity 考察是供给还是需求曲线移动。 Examine whether the supply or demand curve shifts. 确定曲线移动的方向。 Determine the direction of the shift of the curve. 用供求图说明市场均衡如何变化。 Use the supply-and-demand diagram to see how the market equilibrium changes. 小麦市场上供给增加 An Increase in Supply in the Market for Wheat $3 小麦的数量 Quantity of Wheat 0 100 小麦的价格 Price of Wheat 需求 Demand S1 3. …而销售量却只能以更小的比例增加。 结果，收益从$300下降到$220。 and a proportionately smaller increase in quantity sold. As a result, revenue falls from $300 to $220. 小麦市场上供给增加 An Increase in Supply in the Market for Wheat $3 小麦的数量 0 100 Quantity of Wheat Price of Wheat 1. 当需求缺乏弹性时，供给增加 When demand is inelastic, an increase in supply... 需求 Demand S1 S2 2 110 2. …引起价 格的大幅度 下降 Leads to a large fall in price... 计算弹性 Compute Elasticity -0.24 0.4 -0.095 (3.00 2.00)/2 3.00-2.00 (100 110)/2 100-110 ED = = ≈ + + 计算弹性 Compute Elasticity -0.24 0.4 -0.095 (3.00 2.00)/2 3.00-2.00 (100 110)/2 100-110 ED = = ≈ + + 需求是缺乏弹性的 Demand is inelastic 政策含义 Policy Implications 随着农业的技术（或制度）进步，农 产品供给增加和农民数量减少具有某 种必然性 1948年美国有17％人口为农民， 1993年仅有2％。但农业产量为原 来的2倍多。 1952年中国84%劳动力在农业， 1999年为50%。农业产量增加了3 倍
总结 总结 Summary Summa 价格弹性衡量了需求量对价格变化作出反应的 ◆供给价格弹性衡量了供给量对价格变化作出 quantity demanded responds to changes in the price. The price elasticity of supply measures how 如果需求曲线富于弹性,价格上升会导致总收益下 much the quantity supplied responds to changes in the price If a demand curve is elastic, total revenue falls when 在大多数市场上,供给在长期比在短期更富 ◆如果需求曲线峡乏弹性,价格上升会导致总收益上 于弹性 In most markets, supply is more elastic in the If it is inelastic, total revenue rises as the price rises. long run than in the short run
10 总结 Summary 需求价格弹性衡量了需求量对价格变化作出反应的 程度。 Price elasticity of demand measures how much the quantity demanded responds to changes in the price. 如果需求曲线富于弹性，价格上升会导致总收益下 降。 If a demand curve is elastic, total revenue falls when the price rises. 如果需求曲线缺乏弹性，价格上升会导致总收益上 升。 If it is inelastic, total revenue rises as the price rises. 总结 Summary 供给价格弹性衡量了供给量对价格变化作出 反应的程度。 The price elasticity of supply measures how much the quantity supplied responds to changes in the price. 在大多数市场上，供给在长期比在短期更富 于弹性 。 In most markets, supply is more elastic in the long run than in the short run