1、Elasticity and Its Application弹性及其应用弹性及其应用Chapter 5Harcourt, Inc. items and derived items copyright 2001 by Harcourt, Inc.Elasticity . . . 弹性弹性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是衡量买者和卖者对市场条件变动的反应大小的指标。反应大小的指标。u allows us to analyze
2、 supply and demand with greater precision.使我们可以更精确地分析供给与需求使我们可以更精确地分析供给与需求Harcourt, Inc. items and derived items copyright 2001 by Harcourt, Inc.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 o
3、f how much the quantity demanded of a good responds to a change in the price of that good.Harcourt, Inc. items and derived items copyright 2001 by Harcourt, Inc.需求的价格弹性需求的价格弹性u需求的价格弹性需求的价格弹性价格变化价格变化1%引引起的需求量的变化百分比值。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它是一种物品的需求量对其价格变动的反应程度的衡量。的反应程度的衡量。Harcourt, Inc. items
4、 and derived items copyright 2001 by Harcourt, Inc.Determinants of Price Elasticity of Demand需求价格弹性的决定因素需求价格弹性的决定因素uNecessities versus Luxuries 必需品与奢侈品必需品与奢侈品uAvailability of Close Substitutes 相近替代品的可获得性相近替代品的可获得性uDefinition of the Market 市场的定义市场的定义uTime Horizon 时间的长短时间的长短Harcourt, Inc. items and de
5、rived items copyright 2001 by Harcourt, Inc.Determinants of Price Elasticity of DemandDemand tends to be more elastic :uif the good is a luxury.uthe longer the time period.uthe larger the number of close substitutes.uthe more narrowly defined the market.Harcourt, Inc. items and derived items copyrig
6、ht 2001 by Harcourt, Inc.价格需求弹性的决定因素价格需求弹性的决定因素需求倾向于富有弹性：需求倾向于富有弹性：u如果物品是奢侈品如果物品是奢侈品u时期更长时期更长u相近替代品的数量更多相近替代品的数量更多u市场定义的范围更窄市场定义的范围更窄Harcourt, Inc. items and derived items copyright 2001 by Harcourt, Inc.Computing the Price Elasticity of DemandThe price elasticity of demand is computed as the percen
7、tage change in the quantity demanded divided by the percentage change in price.Price Elasticity of Demand =Percentage Changein Quantity DemandedPercentage Changein PricePrice Elasticity of Demand =Percentage Changein Quantity DemandedPercentage Changein PriceHarcourt, Inc. items and derived items co
8、pyright 2001 by Harcourt, Inc.计算需求价格弹性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。分比来计算需求价格弹性。=需求量变动的百分比需求价格弹性价格变动的百分比Harcourt, Inc. items and derived items copyright 2001 by Harcourt, Inc.Computing the Price Elasticity of Demandprice inchange Percentagedemandedquatity inchange Percentag
9、edemand of elasticityPrice 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:2percent10percent2010000200220210010810.).()(Harcourt, Inc. items and derived items copyright 2001
10、 by Harcourt, Inc.计算需求价格弹性计算需求价格弹性需求量变动的百分比需求价格弹性价格变动的百分比例子例子: 如果冰激凌蛋卷的价格从如果冰激凌蛋卷的价格从2美元上升到美元上升到2.2美元，你的购买量从美元，你的购买量从10个下降到个下降到8个，你的个，你的需求价格弹性计算如下：需求价格弹性计算如下：(108)10020102(2.202.00)101002.00Harcourt, Inc. items and derived items copyright 2001 by Harcourt, Inc.The Midpoint Method: A Better Way to Ca
11、lculate 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.)/2P)/(PP(P)/2Q)/(QQ(Q=Demand of Elasticity Price12121212Harcourt, Inc. items and derived items cop
12、yright 2001 by Harcourt, Inc.中点法中点法:一种计算百分比变化一种计算百分比变化和弹性的更好方法和弹性的更好方法中点法中点法 是计算需求价格弹性的更好方法，因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，中点法给出了同一为无论变动的方向如何，中点法给出了同一个答案。个答案。21212121(QQ )/(QQ )/2=(PP )/(PP )/2需求价格弹性Harcourt, Inc. items and derived items copyright 2001 by Harcourt, Inc.The Midpoint Method: A Better Way
13、 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:32. 25 . 9222/ )20. 200. 2()00. 220. 2(2/ )810()
14、810(percentpercent)/2P)/(PP(P)/2Q)/(QQ(Q=Demand of Elasticity Price12121212Harcourt, Inc. items and derived items copyright 2001 by Harcourt, Inc.中点法中点法:一种计算百分比变化和弹性的更好方法一种计算百分比变化和弹性的更好方法例子例子:如果冰激凌蛋卷的价格从如果冰激凌蛋卷的价格从2美元上升到美元上升到2.2美元，你的购买量从美元，你的购买量从10个下降到个下降到8个，利用个，利用中中点法点法你的需求价格弹性计算如下：你的需求价格弹性计算如下：(10
15、8)22(108)/22.32(2.202.00)9.5(2.002.20)/221212121(QQ )/(QQ )/2=(PP )/(PP )/2需求价格弹性Harcourt, Inc. items and derived items copyright 2001 by Harcourt, Inc.The Variety of Demand CurvesInelastic DemanduQuantity demanded does not respond strongly to price changes.uPrice elasticity of demand is less than o
16、ne.Elastic DemanduQuantity demanded responds strongly to changes in price.uPrice elasticity of demand is greater than one.Harcourt, Inc. items and derived items copyright 2001 by Harcourt, Inc.多种需求曲线多种需求曲线缺乏弹性的需求缺乏弹性的需求u需求量不随着价格变化而强烈变化。需求量不随着价格变化而强烈变化。u需求价格弹性小于需求价格弹性小于1。富有弹性的需求富有弹性的需求u需求量随着价格变化而强烈变化
17、。需求量随着价格变化而强烈变化。u需求价格弹性大于需求价格弹性大于1。Harcourt, Inc. items and derived items copyright 2001 by Harcourt, Inc.Computing the Price Elasticity of Demand计算需求的价格弹性计算需求的价格弹性Demand is price elastic需求富有弹性需求富有弹性$54Demand需求需求Quantity数量数量1000Price价格价格50D(100-50)(100 50)/2E(4.00-5.00)(4.00 5.00)/267 -3-22 Harcourt
18、, Inc. items and derived items copyright 2001 by Harcourt, Inc.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 percen
19、tage as the price.Harcourt, Inc. items and derived items copyright 2001 by Harcourt, Inc.多种需求曲线多种需求曲线u完全无弹性完全无弹性 需求量不随价格变化而变化。需求量不随价格变化而变化。u完全弹性完全弹性 价格极小变化引起需求量极大变动。价格极小变化引起需求量极大变动。u单位弹性单位弹性 需求量与价格同比例变动。需求量与价格同比例变动。Harcourt, Inc. items and derived items copyright 2001 by Harcourt, Inc.A Variety of D
20、emand Curves多种需求弹性曲线多种需求弹性曲线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。程度，所以它与需求曲线的斜率密切相关。Harcourt, Inc. items and derived item
21、s copyright 2001 by Harcourt, Inc.Perfectly Inelastic Demand Elasticity equals 0完全无弹性的需求完全无弹性的需求弹性等于弹性等于0Quantity 数量数量Price价格价格4$5Demand 需求需求1002. .leaves the quantity demanded unchanged.2.需求量不变。需求量不变。1. Anincreasein price.1.价格上价格上升升Harcourt, Inc. items and derived items copyright 2001 by Harcourt,
22、Inc.Inelastic Demand Elasticity is less than 1缺乏弹性的需求缺乏弹性的需求弹性小于弹性小于1Quantity 数量数量Price价格价格4$51. A 22%increasein price.1.价格上升价格上升22Demand 需求需求100902. .leads to a 11% decrease in quantity.2.使需求量减少使需求量减少11%。Harcourt, Inc. items and derived items copyright 2001 by Harcourt, Inc.Unit Elastic Demand Elas
23、ticity equals 1单位需求弹性单位需求弹性弹性等于弹性等于1Quantity 数量数量Price价格价格4$51. A 22%increasein price.1.价格上升价格上升22Demand 需求需求100802. .leads to a 22% decrease in quantity.2.使需求量减少使需求量减少22。Harcourt, Inc. items and derived items copyright 2001 by Harcourt, Inc.Elastic Demand Elasticity is greater than 1富有弹性的需求富有弹性的需求弹
24、性大于弹性大于1Quantity 数量数量Price价格价格4$51. A 22%increasein price.1.价格上升价格上升22Demand需求需求100502. .leads to a 67% decrease in quantity.2.使需求量减少使需求量减少67。Harcourt, Inc. items and derived items copyright 2001 by Harcourt, Inc.Perfectly Elastic Demand- Elasticity equals infinityQuantityPriceDemand$41. At any pric
25、eabove $4, quantitydemanded is zero.2. At exactly $4,consumers willbuy any quantity.3. At a price below $4,quantity demanded is infinite.Harcourt, Inc. items and derived items copyright 2001 by Harcourt, Inc.完全富有弹性完全富有弹性弹性等于无穷大弹性等于无穷大数量数量价格价格需求需求$41.在任何高于在任何高于4美元价格时，美元价格时，需求量为需求量为02. 在价格正好为在价格正好为4美元
26、时，消费者美元时，消费者将购买任何一种数量。将购买任何一种数量。3. 价格低于价格低于4美元时，需求量美元时，需求量是无限的。是无限的。Harcourt, Inc. items and derived items copyright 2001 by Harcourt, Inc.Total Revenue and the Price Elasticity of Demand 总收益与需求价格弹性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. 总收益总收益是一种物品买者
27、的支付量和卖者得到的量。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。用该物品的价格乘以销售量来计算。TR = P x QHarcourt, Inc. items and derived items copyright 2001 by Harcourt, Inc.$4Demand 需求需求Quantity数量数量P0Price价格价格P x Q = $400 (total revenue 总收益总收益)100QTotal Revenue and the
28、Price Elasticity of Demand 总收益与需求价格弹性总收益与需求价格弹性Harcourt, Inc. items and derived items copyright 2001 by Harcourt, Inc.Elasticity and Total Revenue along a Linear Demand Curve 沿着线性需求曲线的弹性与总收益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 pr
29、oportionately smaller. Thus, total revenue increases. 如果需求是如果需求是缺乏弹性缺乏弹性的，价格上升导致需的，价格上升导致需求量减少的比例小于价格上升的比例，所求量减少的比例小于价格上升的比例，所以以总收益是增加的。总收益是增加的。Harcourt, Inc. items and derived items copyright 2001 by Harcourt, Inc.Figure 3 How Total Revenue Changes When Price Changes: Inelastic Demand$3Quantity0Pri
30、ce80Revenue = $240 Demand$1DemandQuantity0Revenue = $100100 PriceAn increase in price from $1 to $3.leads to an increase in total revenue from$100 to $240Harcourt, Inc. items and derived items copyright 2001 by Harcourt, Inc.图图3.总收益如何随着价格变化而变化：总收益如何随着价格变化而变化： 缺乏弹性的需求缺乏弹性的需求$3数量数量0价格价格80收益收益=240美元美元
31、需求需求$1需求需求数量数量0收益收益 = 100美元美元100 价格价格价格从价格从1美元上升到美元上升到3美元美元.导致总收益从导致总收益从100美美元元增加增加到到240美元美元Harcourt, Inc. items and derived items copyright 2001 by Harcourt, Inc.Elasticity and Total Revenue along a Linear Demand Curve 沿着线性需求曲线的弹性与总收益沿着线性需求曲线的弹性与总收益With an elastic demand curve, an increase in the p
32、rice leads to a decrease in quantity demanded that is proportionately larger. Thus, total revenue decreases.如果需求如果需求富有弹性，富有弹性，价格上升导致的需求价格上升导致的需求量减少的比例大于价格上升的比例，因此量减少的比例大于价格上升的比例，因此总收益是减少总收益是减少的。的。Harcourt, Inc. items and derived items copyright 2001 by Harcourt, Inc.Figure 4 How Total Revenue Change
33、s 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 $100Harcourt, Inc. items and derived items copyright 2001 by Harcourt, Inc.图图4.总收益如何随着价格变化而变化：总收益如何随着价
34、格变化而变化： 富有弹性的需求富有弹性的需求需求需求数量数量0价格价格$450数量数量数量数量0价格价格收益收益 = 100美元美元 $520收益收益 =200美元美元 价格从价格从4美元上升到美元上升到5美元美元导致总收益从导致总收益从200美美元元减少减少到到100美元美元Harcourt, Inc. items and derived items copyright 2001 by Harcourt, Inc.the Elasticity of a Linear Demand CurvePriceQuantityTotal Revenue(Price xQuantity)Percent
35、Changein PricePercentChangein QuantityElasticityDescription$014$0200%15%0.1Inelastic1121267180.3Inelastic2102040220.6Inelastic382429291Unit elastic462422401.8elastic542018673.7elastic62121520013elastic700 Harcourt, Inc. items and derived items copyright 2001 by Harcourt, Inc.线性需求曲线的弹性线性需求曲线的弹性价格价格数量
36、数量总收益（价格总收益（价格X数量）数量）价格变动百分价格变动百分比比数量变动百分数量变动百分比比弹性弹性弹性程度弹性程度$014$0200%15%0.1缺乏弹性缺乏弹性1121267180.3缺乏弹性缺乏弹性2102040220.6缺乏弹性缺乏弹性382429291单位弹性单位弹性462422401.8富有弹性富有弹性542018673.7富有弹性富有弹性62121520013富有弹性富有弹性700 Harcourt, Inc. items and derived items copyright 2001 by Harcourt, Inc.Income Elasticity of Deman
37、duIncome 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.Harcourt, Inc. items and derived items copyright 2001 by Harcourt, In
38、c.需求的收入弹性需求的收入弹性u需求的收入弹性需求的收入弹性 衡量消费者收入变动衡量消费者收入变动时需求量如何变动。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它是需求量变动的百分比除以收入变动的百分比。动的百分比。Harcourt, Inc. items and derived items copyright 2001 by Harcourt, Inc. Computing Income Elasticity计算收入弹性计算收入弹性Income Elasticityof Demand需求的收入弹性需求的收入弹性Percentage Change in Quantity Deman
39、dedPercentage Change in Income收入变动百分比收入变动百分比=需求量变动百分比需求量变动百分比Harcourt, Inc. items and derived items copyright 2001 by Harcourt, Inc.Income Elasticity- Types of Goods收入弹性：不同类型的物品收入弹性：不同类型的物品uNormal Goods 正常物品正常物品uInferior Goods 劣等品劣等品uHigher income raises the quantity demanded for normal goodsbut low
40、ers the quantity demanded for inferior goods. 正常物品：正常物品：收入提高增加需求量；收入提高增加需求量；劣等品：劣等品：收收入增加减少需求量。入增加减少需求量。Harcourt, Inc. items and derived items copyright 2001 by Harcourt, Inc.Income Elasticity - Types of Goods -uGoods consumers regard as necessities tend to be income inelasticExamples include food,
41、fuel, clothing, utilities, and medical services.uGoods consumers regard as luxuries tend to be income elastic.Examples include sports cars, furs, and expensive foods.Harcourt, Inc. items and derived items copyright 2001 by Harcourt, Inc.收入弹性：不同类型的物品收入弹性：不同类型的物品u消费者消费的必需品往往消费者消费的必需品往往收入弹性小收入弹性小 例如：食物
42、、燃油、衣服、医疗服务。例如：食物、燃油、衣服、医疗服务。u消费者消费的奢侈品往往消费者消费的奢侈品往往收入弹性大收入弹性大例如：运动跑车、皮衣和昂贵物品。例如：运动跑车、皮衣和昂贵物品。Harcourt, Inc. items and derived items copyright 2001 by Harcourt, Inc.需求的交叉价格弹性需求的交叉价格弹性需求的交叉需求的交叉价格弹性价格弹性物品物品1需求量变动百分比需求量变动百分比物品物品2价格变动百分比价格变动百分比=替代品：替代品： E0互补品：互补品： E0无关物品：无关物品：E0Harcourt, Inc. items and
43、 derived items copyright 2001 by Harcourt, Inc.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.Harc
44、ourt, Inc. items and derived items copyright 2001 by Harcourt, Inc.供给的价格弹性供给的价格弹性u供给价格弹性供给价格弹性价格变动价格变动1引起的引起的供給量的变动百分比值。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它是一种物品的供給量对其价格变动的反应程度的衡量。的反应程度的衡量。Harcourt, Inc. items and derived items copyright 2001 by Harcourt, Inc.Perfectly Inelastic Supply Elasticity equals 0完
45、全无弹性的供给：弹性等于完全无弹性的供给：弹性等于0Quantity 数量数量Price价格价格4$5Supply 供给供给1002. .leaves the quantity supplied unchanged.2. 供給量不变。供給量不变。1. Anincreasein price.1.价格上价格上升升Harcourt, Inc. items and derived items copyright 2001 by Harcourt, Inc.Inelastic Supply Elasticity is less than 1缺乏弹性的供给：弹性小于缺乏弹性的供给：弹性小于1Quantit
46、y 数量数量Price价格价格4$51. A 22%increasein price.1.价格上价格上升升22110100Supply 供给供给2. .leads to a 10% increase in quantity.2. 引起供給量增加引起供給量增加10。Harcourt, Inc. items and derived items copyright 2001 by Harcourt, Inc.Unit Elastic SupplyElasticity equals 1单位弹性供给：弹性等于单位弹性供给：弹性等于1Quantity 数量数量Price价格价格4$51. A 22%inc
47、reasein price.1.价格上价格上升升22125100Supply 供给供给2. .leads to a 22% increase in quantity.2. 引起供給量增加引起供給量增加22。Harcourt, Inc. items and derived items copyright 2001 by Harcourt, Inc.Elastic Supply Elasticity is greater than 1富有弹性的供给：弹性大于富有弹性的供给：弹性大于1Quantity 数量数量Price价格价格4$51. A 22%increasein price.1.价格上价格上
48、升升22200100Supply 供给供给2. .leads to a 67% increase in quantity.2. 引起供給量增加引起供給量增加67。Harcourt, Inc. items and derived items copyright 2001 by Harcourt, Inc.Perfectly Elastic Supply Elasticity equals infinity完全有弹性的供给：弹性等于无穷大完全有弹性的供给：弹性等于无穷大Quantity 数量数量Price价格价格Supply 供给供给$41. At any price above $4, quan
49、titysupplied is infinite.1.在任何高于在任何高于4美元的价格时，美元的价格时，供給量无限。供給量无限。2. At exactly $4, producers willsupply any quantity.2.在正好为在正好为4美元时，生产者美元时，生产者供给任何一种数量。供给任何一种数量。3. At a price below $4, quantity supplied is zero.3.在价格低于在价格低于4美元时，供給量为美元时，供給量为0。Harcourt, Inc. items and derived items copyright 2001 by Har
50、court, Inc.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.Harcourt, Inc. items and derived items copyright 200
