经济学原理曼昆第04章.ppt

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1、,2 SUPPLY AND DEMAND I:HOW MARKETS WORK供给与需求（I）：市场如何运行,The Market Forces of Supply and Demand供给与需求的市场力量,Chapter 4,The Market Forces of Supply and Demand,Supply and demand are the two words that economists use most often.Supply and demand are the forces that make market economies work.Modern microeco

2、nomics is about supply,demand,and market equilibrium.,供给与需求的市场力量,供给和需求是经济学家最常用的两个词。供给和需求是让市场经济运行的力量。现代微观经济学就是关于供给、需求和市场均衡的学科。,Markets,A market is a group of buyers and sellers of a particular good or service.The terms supply and demand refer to the behavior of people.as they interact with one anothe

3、r in markets.,市场,市场 是指某种物品或劳务的一群买者与卖者的集合。供给与需求这两个术语是指人们在市场上相互交易时的行为。,Markets and competition 市场与竞争,Buyers determine demand.买者决定需求,Sellers determine supply.卖者决定供给,A Competitive Market 竞争市场,A competitive market is a market in which there are many buyers and sellers so that each has a negligible impact

4、 on the market price 竞争市场有很多买者和卖者的市场，所以每一个买者或卖者对市场价格的影响都可以忽略不计。,Competition:Perfect and Otherwise,Products are the sameNumerous buyers and sellers so that each has no influence over priceBuyers and Sellers are price takers,Perfect Competition,竞争:完全及其它,产品是完全相同的。买者和卖者如此之多，以至于没有一个买者或卖者可以影响价格。买者和卖者都是价格接

5、受者。,完全竞争,Competition:Perfect and Otherwise,MonopolyOne seller,and seller controls priceOligopolyFew sellersNot always aggressive competition,竞争:完全及其它,垄断一个卖者，卖者决定价格。寡头少数几个卖者。并不总是主动地进行竞争。,Competition:Perfect and Otherwise,Monopolistic CompetitionMany sellersSlightly differentiated productsEach seller

6、may set price for its own product,竞争:完全及其它,垄断竞争许多卖者略有差异的产品每个卖者都有决定自己产品价格的能力,Demand 需求,Quantity demanded is the amount of a good that buyers are willing and able to purchase.需求量是指买者愿意而且能够购买的一种物品或劳务的数量。,Law of Demand 需求规律,The law of demand states that there is an inverse relationship between price and

7、 quantity demanded.需求规律认为，价格与需求量之间的关系是负关系。,Demand Schedule 需求表,The demand schedule is a table that shows the relationship between the price of the good and the quantity demanded.需求表 表示一种物品的价格与需求量之间关系的表格。,Catherines Demand Schedule 凯瑟琳的需求表,Demand Curve 需求曲线,The demand curve is the downward-sloping li

8、ne relating price to quantity demanded.需求曲线把价格与需求量联系在一起的向右下方倾斜的曲线。,Figure 1 Catherines Demand Schedule and Demand Curve,Price of,Ice-Cream Cone,0,2.50,2.00,1.50,1.00,0.50,1,2,3,4,5,6,7,8,9,10,11,Quantity of,Ice-Cream Cones,$3.00,12,图1.Catherine的需求表和需求曲线,冰激凌蛋卷的价格,0,2.50,2.00,1.50,1.00,0.50,1,2,3,4,5,

9、6,7,8,9,10,11,冰激凌蛋卷需求量,$3.00,12,Market Demand versus Individual Demand,Market demand refers to the sum of all individual demands for a particular good or service.Graphically,individual demand curves are summed horizontally to obtain the market demand curve.,市场需求,市场需求 是指所有个人对某种物品或劳务需求的总和。从图形上看,把个人需求曲

10、线水平相加，就得出了市场需求曲线。,Change in Quantity Demanded versus Change in Demand,Change in Quantity DemandedMovement along the demand curve.Caused by a change in the price of the product.,需求量的变化与需求的变化,需求量的变化沿着需求曲线移动。是由于产品价格变动引起的。,0,D,Price of Ice-Cream Cones,Quantity of Ice-Cream Cones,A tax that raises the pr

11、ice of ice-cream cones results in a movement along the demand curve.,A,8,1.00,Changes in Quantity Demanded,0,D,冰激凌蛋卷的价格,冰激凌蛋卷的消费量,提高冰激凌蛋卷价格的税收引起沿着需求曲线的移动,A,8,1.00,需求量的变化,Shifts in the Demand Curve,Consumer incomePrices of related goodsTastesExpectationsNumber of buyers,需求曲线的移动,消费者收入相关产品价格嗜好预期买者数量,Sh

12、ifts in the Demand Curve,Change in DemandA shift in the demand curve,either to the left or right.Caused by a change in a determinant other than the price.,需求曲线的移动,需求的变化需求曲线的移动，向左或者向右。是由价格以外的因素变化引起的。,Shifts in the Demand Curve,0,D1,Price of Ice-Cream Cone,Quantity of Ice-Cream Cones,D3,D2,Increase in

13、 demand,Decrease in demand,需求曲线的移动,0,D1,冰激凌蛋卷的价格,冰激凌蛋卷的数量,D3,D2,需求增加,需求减少,Consumer Income 消费者收入,As income increases the demand for a normal good will increase.收入增加，正常商品的需求增加As income increases the demand for an inferior good will decrease.收入增加，劣等品的需求减少,Consumer IncomeNormal Good,$3.00,2.50,2.00,1.50

14、,1.00,0.50,2,1,3,4,5,6,7,8,9,10,12,11,Price of Ice-Cream Cone,Quantity of Ice-Cream Cones,0,Increasein demand,An increase in income.,D1,D2,消费者收入 正常商品,$3.00,2.50,2.00,1.50,1.00,0.50,2,1,3,4,5,6,7,8,9,10,12,11,冰激凌蛋卷的价格,冰激凌蛋卷的数量,0,需求增加,收入增加.,D1,D2,Consumer IncomeInferior Good,$3.00,2.50,2.00,1.50,1.00,

15、0.50,2,1,3,4,5,6,7,8,9,10,12,11,Price of Ice-Cream Cone,Quantity of Ice-Cream Cones,0,Decreasein demand,An increase in income.,D1,D2,消费者收入 劣等品,$3.00,2.50,2.00,1.50,1.00,0.50,2,1,3,4,5,6,7,8,9,10,12,11,冰激凌蛋卷的价格,冰激凌蛋卷的数量,0,需求减少,收入增加.,D1,D2,Prices of Related GoodsSubstitutes&Complements,When a fall in

16、the price of one good reduces the demand for another good,the two goods are called substitutes.When a fall in the price of one good increases the demand for another good,the two goods are called complements.,相关物品的价格替代品和互补品,当一种物品价格下降减少了另一种物品需求时，这两种物品被称为替代品。当一种物品价格下降增加了另一种物品需求时，这两种物品被称为互补品。,Table 1 Va

17、riables That Influence Buyers,Copyright2004 South-Western,表1.影响买者的变量,Supply 供给,Quantity supplied is the amount of a good that sellers are willing and able to sell.供給量是指卖者愿意而且能够出售的一种物品或劳务的数量。,Law of Supply 供给规律,The law of supply states that there is a direct(positive)relationship between price and qu

18、antity supplied.供给规律认为，价格与供給量之间的关系是正关系。,Supply Schedule 供给表,The supply schedule is a table that shows the relationship between the price of the good and the quantity supplied.供给表是表示一种物品价格与供給量之间关系的表格。,Bens Supply Schedule 供给表,Supply Curve 供给曲线,The supply curve is the upward-sloping line relating pric

19、e to quantity supplied.供给曲线把价格与供給量联系在一起的向右上方倾斜的曲线。,Figure 5 Bens Supply Schedule and Supply Curve,rice of,Ice-Cream,Cone,0,2.50,2.00,1.50,1.00,1,2,3,4,5,6,7,8,9,10,11,Quantity of,Ice-Cream Cones,$3.00,12,0.50,图5.Ben供给表与供给曲线,冰激凌蛋卷需求量,0,2.50,2.00,1.50,1.00,1,2,3,4,5,6,7,8,9,10,11,冰激凌蛋卷的供給量,$3.00,12,0.

20、50,Market Supply versus Individual Supply,Market supply refers to the sum of all individual supplies for all sellers of a particular good or service.Graphically,individual supply curves are summed horizontally to obtain the market supply curve.,市场供给,市场供给 是指某种物品或劳务的所有卖者个人供给的总和。从图形上看,把个人供给曲线水平相加，就得出了市

21、场供给曲线。,Shifts in the Supply Curve,Input pricesTechnologyExpectations Number of producers,供给曲线的移动,投入要素价格技术预期 生产者数量,Change in Quantity Supplied versus Change in Supply,Change in Quantity SuppliedMovement along the supply curve.Caused by a change in the market price of the product.,供給量的变化与供给的变化,供給量的变化沿

22、着供给曲线移动。是由于产品的市场价格变动引起的。,Change in Quantity Supplied,1,5,Price of Ice-Cream Cone,Quantity of Ice-Cream Cones,0,S,1.00,A,C,A rise in the price of ice cream cones results in a movement along the supply curve.,供給量的变化,1,5,冰激凌蛋卷的价格,冰激凌蛋卷的数量,0,S,1.00,A,C,冰激凌蛋卷的市场价格上升导致供給量沿着供给曲线的移动。,Shifts in the Supply Cu

23、rve,Change in SupplyA shift in the supply curve,either to the left or right.Caused by a change in a determinant other than price.,供給曲线的移动,供给的变化供给曲线的移动，向左或者向右。是由于价格以外的因素变化造成的。,Shifts in the Supply Curve,Price of Ice-Cream Cone,Quantity of Ice-Cream Cones,0,S1,供给曲线的移动,冰激凌蛋卷的价格,冰激凌蛋卷的数量,0,S1,Table 2 Va

24、riables That Influence Sellers,供給量的变化与供给的变化,SUPPLY AND DEMAND TOGETHER供给与需求的结合,Equilibrium refers to a situation in which the price has reached the level where quantity supplied equals quantity demanded.市场均衡 价格水平达到供給量与需求量相等的状态。,Supply and Demand Together,Equilibrium PriceThe price that balances supp

25、ly and demand.On a graph,it is the price at which the supply and demand curves intersect.Equilibrium QuantityThe quantity that balances supply and demand.On a graph it is the quantity at which the supply and demand curves intersect.,供给与需求的结合,均衡价格使供给与需求平衡的价格。从图形上看，就是供给曲线与需求曲线相交时的价格。均衡数量当价格调整到使供给与需求平衡

26、时的供給量与需求量。从图形上看，就是供给曲线与需求曲线相交时的数量。,Supply and Demand Together,Demand Schedule,Supply Schedule,At$2.00,the quantity demanded is equal to the quantity supplied!,供给与需求的结合,需求表,供给表,在$2.00时,需求量等于供給量!,Figure 8 The Equilibrium of Supply and Demand,Copyright2003 Southwestern/Thomson Learning,Price of,Ice-Cre

27、am,Cone,0,1,2,3,4,5,6,7,8,9,10,11,12,Quantity of Ice-Cream Cones,13,表8.供给与需求的均衡,冰激凌蛋卷需求量,0,1,2,3,4,5,6,7,8,9,10,11,12,冰激凌蛋卷的数量,13,Figure 9 Markets Not in Equilibrium,Price of,Ice-Cream,Cone,0,(a)Excess Supply,Quantity of,Ice-Cream,Cones,图9.非均衡状态的市场,冰激凌蛋卷需求量,0,(a)超额供给,冰激凌蛋卷的数量,Equilibrium,SurplusWhen

28、 price equilibrium price,then quantity supplied quantity demanded.There is excess supply or a surplus.Suppliers will lower the price to increase sales,thereby moving toward equilibrium.,均衡,过剩当价格高于均衡价格时，供給量大于需求量。存在超额供给或过剩。供给者通过降低价格来增加销售，这使价格向其均衡水平变动。,Equilibrium,ShortageWhen price the quantity suppli

29、ed.There is excess demand or a shortage.Suppliers will raise the price due to too many buyers chasing too few goods,thereby moving toward equilibrium.,均衡,短缺当价格低于市场均衡价格时，需求量超过了供給量。存在着超额需求或短缺。由于太多卖者要购买太少的物品，供给者将提高价格。因此价格将趋向于市场均衡价格。,Figure 9 Markets Not in Equilibrium,Price of,Ice-Cream,Cone,0,Quantity

30、 of,Ice-Cream,Cones,(b)Excess Demand,图9.非均衡状态的市场,冰激凌蛋卷需求量,0,冰激凌蛋卷的数量,(b)超额需求,Equilibrium 均衡,Law of supply and demand 需求规律The claim that the price of any good adjusts to bring the quantity supplied and the quantity demanded for that good into balance.认为任何一种物品价格的调整都会使该物品供求平衡的观点。,Three Steps To Analyzi

31、ng Changes in Equilibrium,Decide whether the event shifts the supply or demand curve(or both).Decide whether the curve(s)shift(s)to the left or to the right.Use the supply-and-demand diagram to see how the shift affects equilibrium price and quantity.,分析均衡的三个步骤,确定该事件是使供给曲线移动，还是使需求曲线移动，或者使两种曲线都移动。确定曲

32、线是向右移动，还是向左移动。用供求图来考察这种移动如何影响均衡价格和数量。,How an Increase in Demand Affects the Equilibrium,Price ofIce-CreamCone,2.00,0,7,Quantity ofIce-Cream Cones,Supply,Initialequilibrium,D1,1.Hot weather increasesthe demand for ice cream.,需求增加如何影响均衡,冰激凌蛋卷的价格,2.00,0,7,冰激凌蛋卷的数量,供给,原来的均衡,D1,1.天气热使冰激凌需求增加.,Three Steps

33、 to Analyzing Changes in Equilibrium,Shifts in Curves versus Movements along CurvesA shift in the supply curve is called a change in supply.A movement along a fixed supply curve is called a change in quantity supplied.A shift in the demand curve is called a change in demand.A movement along a fixed

34、demand curve is called a change in quantity demanded.,分析均衡的三个步骤,曲线移动与沿着曲线的移动:供给曲线的移动被称为供给的变化。沿着固定的供给曲线的移动被称为供給量的变化。需求曲线的移动被称为需求的变化。沿着固定的需求曲线的移动被称为需求量的变化。,How a Decrease in Supply Affects the Equilibrium,Price ofIce-CreamCone,2.00,0,1,2,3,4,7,8,9,11,12,Quantity ofIce-Cream Cones,13,Demand,Initial equ

35、ilibrium,S1,10,1.An earthquake reducesthe supply of ice cream.,Newequilibrium,供给减少如何影响均衡,冰激凌蛋卷的价格,2.00,0,1,2,3,4,7,8,9,11,12,冰激凌蛋卷的数量,13,需求,原来的均衡,S1,10,地震减少了冰激凌的供给.,新均衡,What Happens to Price and Quantity When Supply or Demand Shifts?,当供给或需求变动时，价格和数量会发生什么变化?,Summary,Economists use the model of supply

36、 and demand to analyze competitive markets.In a competitive market,there are many buyers and sellers,each of whom has little or no influence on the market price.,小结,经济学家用供求模型来分析竞争市场。在竞争市场中，有许多买者和卖者，他们当中的任何一个对市场价格具有极小或者没有影响力。,Summary,The demand curve shows how the quantity of a good depends upon the

37、price.According to the law of demand,as the price of a good falls,the quantity demanded rises.Therefore,the demand curve slopes downward.In addition to price,other determinants of how much consumers want to buy include income,the prices of complements and substitutes,tastes,expectations,and the numb

38、er of buyers.If one of these factors changes,the demand curve shifts.,小结,需求曲线表示一种物品的需求量如何取决于价格。根据需求规律，当一种物品价格上升时，需求量减少。所以需求曲线是下倾的。除了价格以外，决定需求量的其它因素包括收入、替代品和互补品的价格、嗜好、预期，以及买者的数量。如果这些变量中的任何一个变化，导致需求曲线移动。,Summary,The supply curve shows how the quantity of a good supplied depends upon the price.Accordin

39、g to the law of supply,as the price of a good rises,the quantity supplied rises.Therefore,the supply curve slopes upward.In addition to price,other determinants of how much producers want to sell include input prices,technology,expectations,and the number of sellers.If one of these factors changes,t

40、he supply curve shifts.,小结,供给曲线表示一种物品的供給量如何取决于价格。根据供给规律，当一种物品的价格上升时，供給量增加。所以供给曲线是上倾的。除了价格以外，决定供給量的其它因素包括投入要素的价格、技术、预期，以及卖者的数量。如果这些变量中的任何一个变化，导致供给曲线移动。,Summary,Market equilibrium is determined by the intersection of the supply and demand curves.At the equilibrium price,the quantity demanded equals th

41、e quantity supplied.The behavior of buyers and sellers naturally drives markets toward their equilibrium.,小结,市场均衡是由供给曲线和需求曲线相交决定的。在均衡价格水平上，需求量和供給量相等。买者和卖者的行为自然地驱动 市场走向均衡。,Summary,To analyze how any event influences a market,we use the supply-and-demand diagram to examine how the even affects the equilibrium price and quantity.In market economies,prices are the signals that guide economic decisions and thereby allocate resources.,小结,为了分析一个事件如何影响市场，我们利用供求图来考察这一事件如何影响均衡价格和均衡数量。在市场经济中，价格是指引经济决策从而配置稀缺资源的信号。,