曼昆哈佛大学经济学原理课件第五章

第五章弹性及其应用复习题1．给需求价格弹性与需求收入弹性下定义。

答：需求价格弹性，是指一种物品需求量对其价格变动反应程度的衡量；需求收入弹性，是指一种物品需求量对消费者收入变动反应程度的衡量。

2．列出并解释本章中所谈论的决定需求价格弹性的四个因素。

答：需求的价格弹性取决于许多形成个人欲望的经济、社会与心理因素。

通常，需求价格弹性主要由以下几个因素决定：(1)相似替代品的可获得性。

有相似替代品的物品往往富有需求弹性，因为消费者从这种物品转向其他物品较为容易。

(2)必需品与奢侈品。

必需品倾向于需求缺乏弹性，奢侈品倾向于需求富有弹性。

(3)市场的定义。

范围小的市场的需求弹性往大于范围大的市场，因为范围小的市场上的物品更容易找到相近的替代品。

(4)时间框架。

物品往往随着时间变长而需求更富有弹性，因为在长期中人们有充分的时间来改变自己的消费嗜好与消费结构。

4．如果弹性大于1，需求是富有弹性还是缺乏弹性?如果弹性等于零，需求是完全有弹性还是完全无弹性?答：弹性大于1，需求富有弹性。

弹性等于零，需求完全无弹性。

5．在一个供求图上标明均衡价格、均衡数量与生产者得到的总收益。

答：如图，供给与需求曲线的交点是均衡点，均衡点所对应的价格P是均衡价格，所对应的数量Q是均衡数量。

P·Q，即阴影部分是生产者得到的总收益。

6．如果需求是富有弹性的，价格上升会如何改变总收益?解释原因。

答：如果需求是富有弹性的，价格上升会使总收益减少。

因为需求富有弹性，价格上升引起需求量减少的如此之多，以至于大到抵消价格上涨所带来的收益，即需求量下降的比例大于价格上升的比例。

7．如果一种物品需求收入弹性小于零，我们把这种物品称为什么?答：需求收入弹性小于零的物品，我们称为低档物品。

8．如何计算供给的价格弹性?供给价格弹性衡量什么?答：供给价格弹性＝供给量变动的百分比／价格变动百分比。

它是衡量供给量对其价格变动的反应程度。

9．毕加索油画的供给价格弹性是多大?答：毕加索油画的供给价格弹性为零。

Other Elasticities Cross-price elasticity of demand: measures the response of demand for one good to changes in the price of another good Cross-price elast. = of demand % change in price of good 2 For substitutes, cross-price elasticity > 0 (e.g., an increase in price of beef causes an increase in demand for chicken For complements, cross-price elasticity < 0 (e.g., an increase in price of computers causes decrease in demand for software ELASTICITY AND ITS APPLICATION 45 % change in Qd for good 1CHAPTER SUMMARY Elasticity measures the responsiveness of Qd or Qs to one of its determinants. Price elasticity of demand equals percentage change in Qd divided by percentage change in P. When it’s less than one, demand is “inelastic.” When greater than one, demand is “elastic.” When demand is inelastic, total revenue rises when price rises. When demand is elastic, total revenue falls when price rises. 46CHAPTER SUMMARY Demand is less elastic in the short run, for necessities, for broadly defined goods, or for goods with few close substitutes. Price elasticity of supplyequals percentage change in Qs divided by percentage change in P. When it’s less than one, supply is “inelastic.” When greater than one, supply is “elastic.” Price elasticity of supply is greater in the long run than in the short run. 47CHAPTER SUMMARY The income elasticity of demand measures how much quantity demanded responds to changes in buyers’ incomes. The cross-price elasticity of demand measures how much demand for one good responds to changes in the price of another good. 48。

Chapter5Intrinsic 内在的，本质的Margarine人造黄油Qualitative定性的Quantitative定量的absolute value绝对值numerator分子denominator分母，平均水平keep straight行为正直panel仪表盘，面板，座谈小组variable易变的；变量revenue税收，收入offset抵消，弥补curator博物馆、展览馆等的馆长，管理员caviar鱼子酱THE ELASTICITY OF DEMONDDefinition：To measure how much demand responds to changes in its determinants, economists use the concept of elasticity.——price elasticity of demandRules: Necessities versus Luxuries Necessities tend to have inelastic demands, whereas luxuries have elastic demandsAvailability of Close Substitutes Goods with close substitutes tendto have more elastic demand because it is easier for consumers to switch from thatgood to others.Definition of the Market The elasticity of demand in any market dependson how we draw the boundaries of the market. Narrowly defined marketstend to have more elastic demand than broadly defined marketsTime Horizon Goods tend to have more elastic demand over longer time horizons.Calculating：Economists compute the price elasticity of demand as the percentage change in the quantity demanded divided by the percentage change in the price.TOTAL REVENUE AND THE PRICE ELASTICITY OF DEMAND♉When a demand curve is inelastic (a price elasticity less than 1), a price increase raises total revenue, and a price decrease reduces total revenue.♉ When a demand curve is elastic (a price elasticity greater than 1), a price increase reduces total revenue, and a price decrease raises total revenue.♉ In the special case of unit elastic demand (a price elasticity exactly equal to 1), a change in the price does not affect total revenue.Beachfront海滨地区Incur招致，遭受，惹起Numerical数字的，用数字表示的Interdiction封锁，禁止are subject to服从，遭受，以……为条件bushel蒲式尔（容量单位）hypothetical假定的，假设的primitive原始的，简陋的livestock家畜，牲畜paradox悖论，似是而非的论点at the expense of以……为代价disruptive分裂的，破坏性的，制造混乱的disarray无秩序，混乱prevail盛行，获胜，劝说plunge跳入，投入episode一段情节，轶事，插曲conservation保存，保护，守恒cartel卡特尔，联合企业smuggler走私者pursue追求，追捕，执行quip说俏皮话，妙语THE ELASTICITY OF SUPPLYDefinition：The price elasticity of supply measures how much the quantity supplied responds to changes in the price.Rules：The price elasticity of supply depends on the flexibility of sellers to change the amount of the good they produce.In most markets, a key determinant of the price elasticity of supply is the time period being considered. Supply is usually more elastic in the long run than in the short run. Calculating：Economists compute the price elasticity of supply as the percentage change in the quantity supplied divided by the percentage change in the price。