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1、4,The Market Forces of Supply and Demand-这一章就进入需求和供给的内容了这个很重要，考试肯定会出这里的题,CHAPTER 4 THE MARKET FORCES OF SUPPLY AND DEMAND,In this chapter,look for the answers to these questions:这章涉及到的问题,What factors affect buyers demand for goods?What factors affect sellers supply of goods?哪些因素会影响购买者的需求？哪些因素会影响生产者的
2、供给？How do supply and demand determine the price of a good and the quantity sold?生产和供给如何影响价格和销量的？How do changes in the factors that affect demand or supply affect the market price and quantity of a good?影响供给和需求的因素的改变是如何影响市场价格和商品产量的How do markets allocate resources?市场如何分配（有限）的资源,CHAPTER 4 THE MARKET F
3、ORCES OF SUPPLY AND DEMAND,Markets and Competition,A market is a group of buyers and sellers of a particular product.市场就是某一个特定产品的同时拥有卖方和买方群体的地方。A competitive market is one with many buyers and sellers,each has a negligible effect on price.竞争性市场指的是买方和卖方对于价格的影响微乎其微（由市场做主）A perfectly competitive market
4、:完全竞争市场all goods exactly the same所有的商品都是一样的buyers&sellers so numerous that no one can affect market price each is a“price taker”市场中所有的卖家和买家都不能影响市场价格，每个人都是“价格的接受者”In this chapter,we assume markets are perfectly competitive.这一章中，假设或者说背景市场都是完全竞争市场（这个假设其实是为了过滤掉一些其他影响因素来探究市场的功能，探究供给和需求的关系）,0,CHAPTER 4 TH
5、E MARKET FORCES OF SUPPLY AND DEMAND,Demand,Demand comes from the behavior of buyers.The quantity demanded of any good is the amount of the good that buyers are willing and able to purchase.只有当购买者愿意并且能够购买的时候，才会有购买数量，或者说，购买的需求。Law of demand:the claim that the quantity demanded of a good falls when th
6、e price of the good rises,other things equal 需求法则，很简单，当其他因素都一样的时候，商品的价格升高，其需求量就减少。,0,CHAPTER 4 THE MARKET FORCES OF SUPPLY AND DEMAND,The Demand Schedule需求列表,Demand schedule:A table that shows the relationship between the price of a good and the quantity demanded.Example:Helens demand for lattes.,No
7、tice that Helens preferences obey the Law of Demand.,0,CHAPTER 4 THE MARKET FORCES OF SUPPLY AND DEMAND,Helens Demand Schedule&Curve图中可以看出价格越高，需求量越少,0,Market Demand versus Individual Demand,The quantity demanded in the market is the sum of the quantities demanded by all buyers at each price.市场中所有的需求
8、总量，是每一个购买者在每一个价格点上购买商品的数量的总和。Suppose Helen and Ken are the only two buyers in the Latte market.(Qd=quantity demanded)例子：假设海伦和肯是市场中唯一的两个买家，那么他们的购买量相加就是这个市场的需求总量,Market Qd,0,CHAPTER 4 THE MARKET FORCES OF SUPPLY AND DEMAND,P,Q,The Market Demand Curve for Lattes这个线条，叫做需求曲线，注意它的方向！,0,CHAPTER 4 THE MARKE
9、T FORCES OF SUPPLY AND DEMAND,Demand Curve Shifters,The demand curve shows how price affects quantity demanded,other things being equal.These“other things”are non-price determinants of demand(i.e.,things that determine buyers demand for a good,other than the goods price).Changes in them shift the D
10、curve,0,CHAPTER 4 THE MARKET FORCES OF SUPPLY AND DEMAND,Demand Curve Shifters:#of buyers影响需求曲线的因素：购买者的数量,An increase in the number of buyers causesan increase in quantity demanded at each price,which shifts the demand curve to the right.购买者数量的增加会使需求曲线移动。很简单，买的人多了，需求量就多了。曲线往右移动，看下图,0,CHAPTER 4 THE M
11、ARKET FORCES OF SUPPLY AND DEMAND,Suppose the number of buyers increases.Then,at each price,quantity demanded will increase(by 5 in this example).,Demand Curve Shifters:#of buyers,0,CHAPTER 4 THE MARKET FORCES OF SUPPLY AND DEMAND,Demand for a normal good is positively related to income.An increase
12、in income causes increase in quantity demanded at each price,shifting the D curve to the right.收入越高，买的越多，所以曲线向右移动(Demand for an inferior good is negatively related to income.An increase in income shifts D curves for inferior goods to the left.)（特例，对于劣质商品，当收入越高的时候，其购买量越少，曲线向左移动）,Demand Curve Shifters
13、:income影响需求曲线的因素：购买者收入,0,CHAPTER 4 THE MARKET FORCES OF SUPPLY AND DEMAND,Two goods are substitutes if an increase in the price of one causes an increase in demand for the other.如果两种商品互为替代品，那么一种商品价格的上升会使另一种商品的需求上升。很简单，例如：如果百事可乐的价格上升，那么人们都会去买可口可乐了。这里需要搞清楚替代商品（substitus）的概念，并和后面的互补商品进行区分。Example:pizza
14、 and hamburgers.An increase in the price of pizza increases demand for hamburgers,shifting hamburger demand curve to the right.Other examples:Coke and Pepsi,laptops and desktop computers,compact discs and music downloads,Demand Curve Shifters:prices of related goods影响需求曲线的因素：相关商品的价格,0,CHAPTER 4 THE
15、MARKET FORCES OF SUPPLY AND DEMAND,Two goods are complements if an increase in the price of one causes a fall in demand for the other.如果两种商品互为互补品，那么一种商品价格的上升会是另一种商品的价格下降。例如：电脑和电脑软件。其实，互补商品虽然是两个，但是可以看做一个整体，一个价格涨了，整个整体都会受影响。Example:computers and software.If price of computers rises,people buy fewer co
16、mputers,and therefore less software.Software demand curve shifts left.Other examples:college tuition and textbooks,bagels and cream cheese,eggs and bacon,Demand Curve Shifters:prices of related goods,0,CHAPTER 4 THE MARKET FORCES OF SUPPLY AND DEMAND,Anything that causes a shift in tastes toward a g
17、ood will increase demand for that good and shift its D curve to the right.当购买者喜欢这种商品的口味时，商品的需求量就会增加，曲线右移。比如KFCExample:The KFCs diet became popular in the 90s,caused an increase in demand for eggs,shifted the egg demand curve to the right.,Demand Curve Shifters:tastes影响需求曲线的因素：购买者的口味,0,CHAPTER 4 THE
18、MARKET FORCES OF SUPPLY AND DEMAND,Expectations affect consumers buying decisions.期望影响购买者的决定。例如，如果人们认为他们的收入会增长，那么对于高档商品来说，它的需求量就可能会增加。Examples:If people expect their incomes to rise,their demand for meals at expensive restaurants may increase now.If the economy turns bad and people worry about their
19、 future job security,demand for new autos may fall now.,Demand Curve Shifters:expectations影响需求曲线的因素：购买者的期望,0,CHAPTER 4 THE MARKET FORCES OF SUPPLY AND DEMAND,Summary:Variables That Affect Demand总结：影响需求的要素，这些需要记住，会考的,VariableA change in this variable,Pricecauses a movement along the D curveNo.of buye
20、rsshifts the D curveIncomeshifts the D curvePrice ofrelated goodsshifts the D curveTastesshifts the D curveExpectationsshifts the D curve,0,A C T I V E L E A R N I N G 1:Demand curve需求曲线 的练习，做做吧，不会的再问我,A.The price of iPods fallsB.The price of music downloads fallsC.The price of compact discs falls,1
21、7,Draw a demand curve for music downloads.What happens to it in each of the following scenarios?Why?,A C T I V E L E A R N I N G 1:A.price of iPods falls,18,Music downloads and iPods are complements.A fall in price of iPods shifts the demand curve for music downloads to the right.,A C T I V E L E A
22、R N I N G 1:B.price of music downloads falls,19,The D curve does not shift.Move down along curve to a point with lower P,higher Q.,Price of music down-loads,Quantity of music downloads,D1,P1,Q1,A C T I V E L E A R N I N G 1:C.price of CDs falls,20,CDs and music downloads are substitutes.A fall in pr
23、ice of CDs shifts demand for music downloads to the left.,Price of music down-loads,Quantity of music downloads,CHAPTER 4 THE MARKET FORCES OF SUPPLY AND DEMAND,Supply-供给,Supply comes from the behavior of sellers.需求是购买者的行为，那么供给就是生产者或者销售者的行为了。供给的概念和需求有相反，可以比较着看The quantity supplied of any good is the
24、 amount that sellers are willing and able to sell.Law of supply:the claim that the quantity supplied of a good rises when the price of the good rises,other things equal 供给法则：价格升高，供给量增加（其他因素一样的情况下）-和需求是相反的吧，想想,0,CHAPTER 4 THE MARKET FORCES OF SUPPLY AND DEMAND,The Supply Schedule,Supply schedule:A ta
25、ble that shows the relationship between the price of a good and the quantity supplied.Example:Starbucks supply of lattes.,Notice that Starbucks supply schedule obeys the Law of Supply.,0,CHAPTER 4 THE MARKET FORCES OF SUPPLY AND DEMAND,Starbucks Supply Schedule&Curve,P,Q,0,Market Supply versus Indiv
26、idual Supply市场供给总量的概念和需求一样，每一个销售者在每一个价格点上的销量的总和,The quantity supplied in the market is the sum of the quantities supplied by all sellers at each price.Suppose Starbucks and Jitters are the only two sellers in this market.(Qs=quantity supplied),Market Qs,0,CHAPTER 4 THE MARKET FORCES OF SUPPLY AND DE
27、MAND,The Market Supply Curve,0,CHAPTER 4 THE MARKET FORCES OF SUPPLY AND DEMAND,Supply Curve Shifters,The supply curve shows how price affects quantity supplied,other things being equal.These“other things”are non-price determinants of supply.Changes in them shift the S curve,0,CHAPTER 4 THE MARKET F
28、ORCES OF SUPPLY AND DEMAND,Supply Curve Shifters:input prices影响供给曲线的因素：生产投入价格,Examples of input prices:wages,prices of raw materials.生产投入包括：工资、劳动力成本等A fall in input prices makes production more profitable at each output price,so firms supply a larger quantity at each price,and the S curve shifts to
29、the right.生产投入的降低，会使供给曲线右移（供给量增加）,0,CHAPTER 4 THE MARKET FORCES OF SUPPLY AND DEMAND,Suppose the price of milk falls.At each price,the quantity of Lattes supplied will increase(by 5 in this example).,Supply Curve Shifters:input prices,0,CHAPTER 4 THE MARKET FORCES OF SUPPLY AND DEMAND,Supply Curve S
30、hifters:technology影响供给曲线的因素：科技,Technology determines how much inputs are required to produce a unit of output.A cost-saving technological improvement has same effect as a fall in input prices,shifts the S curve to the right.科技提升，曲线右移,0,CHAPTER 4 THE MARKET FORCES OF SUPPLY AND DEMAND,Supply Curve Sh
31、ifters:#of sellers影响供给曲线的因素：销售者的数量,An increase in the number of sellers increases the quantity supplied at each price,shifts the S curve to the right.销售者的数量增加，曲线右移,0,CHAPTER 4 THE MARKET FORCES OF SUPPLY AND DEMAND,Supply Curve Shifters:expectations 影响供给曲线的因素：期望,Suppose a firm expects the price of t
32、he good it sells to rise in the future.The firm may reduce supply now,to save some of its inventory to sell later at the higher price.This would shift the S curve leftward.如果一个生产商认为该商品以后的价格会上涨，它就会减少目前的供应量来等待未来的高价格，这时候，曲线左移（供给量减少）,0,CHAPTER 4 THE MARKET FORCES OF SUPPLY AND DEMAND,Summary:Variables T
33、hat Affect Supply总结：影响供给的因素,VariableA change in this variable,Pricecauses a movement along the S curveInput pricesshifts the S curveTechnologyshifts the S curveNo.of sellersshifts the S curveExpectationsshifts the S curve,0,A C T I V E L E A R N I N G 2:Supply curve练习,33,Draw a supply curve for tax
34、return preparation software.What happens to it in each of the following scenarios?,0,A.Retailers cut the price of the software.B.A technological advance allows the software to be produced at lower cost.C.Professional tax return preparers raise the price of the services they provide.,A C T I V E L E
35、A R N I N G 2:A.fall in price of tax return software,34,The S curve does not shift.Move down along the curve to a lower P and lower Q.,A C T I V E L E A R N I N G 2:B.fall in cost of producing the software,35,The S curve shifts to the right:at each price,Q increases.,Price of tax return software,Qua
36、ntity of tax return software,S1,P1,Q1,A C T I V E L E A R N I N G 2:C.professional preparers raise their price,36,This shifts the demand curve for tax preparation software,not the supply curve.,CHAPTER 4 THE MARKET FORCES OF SUPPLY AND DEMAND,Supply and Demand Together供给曲线和需求曲线的交叉点，就是平衡点，市场上的商品达到供需平
37、衡,Equilibrium:P has reached the level where quantity supplied equals quantity demanded,0,CHAPTER 4 THE MARKET FORCES OF SUPPLY AND DEMAND,Equilibrium price:平衡点价格,The price that equates quantity supplied with quantity demanded,0,CHAPTER 4 THE MARKET FORCES OF SUPPLY AND DEMAND,Equilibrium quantity:平衡
38、点数量,The quantity supplied and quantity demanded at the equilibrium price,0,CHAPTER 4 THE MARKET FORCES OF SUPPLY AND DEMAND,Surplus:剩余、盈余,when quantity supplied is greater than quantity demanded供给数量大于需求数量，就会产生剩余。注意两个点的位置。,Surplus,Example:If P=$5,then QD=9 lattes,and QS=25 lattes,resulting in a surpl
39、us of 16 lattes,0,CHAPTER 4 THE MARKET FORCES OF SUPPLY AND DEMAND,Surplus:,when quantity supplied is greater than quantity demanded,Facing a surplus,sellers try to increase sales by cutting the price.出现盈余的时候，销售者会尝试减少价格增加销售量,This causes QD to rise,which reduces the surplus.,and QS to fall,0,CHAPTER
40、4 THE MARKET FORCES OF SUPPLY AND DEMAND,Surplus:,when quantity supplied is greater than quantity demanded,Facing a surplus,sellers try to increase sales by cutting the price.,Falling prices cause QD to rise and QS to fall.,Surplus,Prices continue to fall until market reaches equilibrium.价格一直下降直到达到平
41、衡点。,0,相关新闻,第一财经日报报导，内地三十九种行业九百种商品同时出现供过于求的现象，报导指出，近年来由于钢铁价格持续上扬，不少中国企业盲目投资，导致钢材产能严重过剩，四月份起已上涨三年多的钢材价格开始下跌，到五、六月份已经跌破经销成本。新闻来源:大公网,CHAPTER 4 THE MARKET FORCES OF SUPPLY AND DEMAND,CHAPTER 4 THE MARKET FORCES OF SUPPLY AND DEMAND,Shortage:短缺,when quantity demanded is greater than quantity supplied需大于供
42、，注意点的位置,Example:If P=$1,then QD=21 lattes,and QS=5 lattes,resulting in a shortage of 16 lattes,Shortage,0,CHAPTER 4 THE MARKET FORCES OF SUPPLY AND DEMAND,Shortage:,when quantity demanded is greater than quantity supplied,Facing a shortage,sellers raise the price,causing QD to fall,which reduces the
43、 shortage.面对短缺，商家会提示价格，这样需求量就会减少，同时供给量增加。,and QS to rise,0,CHAPTER 4 THE MARKET FORCES OF SUPPLY AND DEMAND,Shortage:,when quantity demanded is greater than quantity supplied,Facing a shortage,sellers raise the price,causing QD to fall,and QS to rise.,Shortage,Prices continue to rise until market re
44、aches equilibrium.最后到达平衡,0,相关新闻,津巴布韦是世界上通胀率最高的国家。根据津中央银行7月中旬提供的数据，津通货膨胀率已达2200000。从2000年津政府实施新的土改政策以来，津巴布韦遭受了西方国家经济制裁和连续干旱的多重打击，经济逐渐陷入困境。虽然政府多次修改政策，制定了许多鼓励经济恢复的计划，但整个国民经济至今还没有好转迹象，津巴布韦经常面临基础商品短缺局面。美元对津元的比价已由年初的比5300急剧升值至比1200亿。,CHAPTER 4 THE MARKET FORCES OF SUPPLY AND DEMAND,CHAPTER 4 THE MARKET FO
45、RCES OF SUPPLY AND DEMAND,Three Steps to Analyzing Changes in Eqm分析平衡点上的改变的步骤,1.Decide whether event shifts S curve,D curve,or both.确定事件是影响需求曲线还是供给曲线，还是两个都影响。Decide in which direction curve shifts.确定曲线往哪个方向移动Use supply-demand diagram to see how the shift changes eqm P and Q.利用图像，找出平衡点，和平衡点时的价格和数量,To
46、 determine the effects of any event,CHAPTER 4 THE MARKET FORCES OF SUPPLY AND DEMAND,EXAMPLE:The Market for Hybrid Cars案例，你自己先看，不明白再问我,相关新闻,通过轻巧的车身和流线的造型来降低油耗从而达到省油的目的，每加仑汽油可行驶约150英里。该车既可燃烧汽油也可燃烧甲醇。由于整车采用碳纤维制成，使得其车体重量降至270千克。这款汽车还提供有多种动力选择。太阳能电池版所吸收的太阳能能够供给其行驶15到25千米。有趣的是，阳光不够强烈时，它甚至可以像自行车一样通过内置的脚踏板
47、来对电池进行充电。该车采用3座设计，将会于2012年投产，预计花费为2万美元。,CHAPTER 4 THE MARKET FORCES OF SUPPLY AND DEMAND,CHAPTER 4 THE MARKET FORCES OF SUPPLY AND DEMAND,STEP 1:D curve shifts because price of gas affects demand for hybrids.S curve does not shift,because price of gas does not affect cost of producing hybrids.,STEP
48、2:D shifts rightbecause high gas price makes hybrids more attractive relative to other cars.,EXAMPLE 1:A Change in Demand,EVENT TO BE ANALYZED:Increase in price of gas.,STEP 3:The shift causes an increase in price and quantity of hybrid cars.,CHAPTER 4 THE MARKET FORCES OF SUPPLY AND DEMAND,EXAMPLE
49、1:A Change in Demand,P2,Q2,Notice:When P rises,producers supply a larger quantity of hybrids,even though the S curve has not shifted.,Always be careful to distinguish a shift in a curve and a movement along the curve.,Terms for Shift vs.Movement Along Curve,Change in supply:a shift in the S curveocc
50、urs when a non-price determinant of supply changes(like technology or costs)供给上的改变，会造成供给曲线的移动，例如科技或者成本的影响。Change in the quantity supplied:供给数量的改变会造成在固定的供给曲线上的点的移动a movement along a fixed S curve occurs when P changes 往往在价格改变时发生Change in demand:a shift in the D curve需求，同理occurs when a non-price deter
