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1、Copyright 2013 Pearson Education,Inc.Microeconomics Pindyck/Rubinfeld,8e.,*of 50,4.1Individual Demand4.2Income and Substitution Effects4.3Market Demand4.4Consumer Surplus4.5Network Externalities4.6Empirical Estimation of DemandAppendix:Demand TheoryA Mathematical Treatment,C H A P T E R 4,Prepared b
2、y:Fernando Quijano,Illustrator,Individual and Market Demand个人需求和市场需求,CHAPTER OUTLINE,饥絮夷惶诽粱衙俊奢嗣组撵制愉碳寅寄猎育懊梆牌翠倦庚红末肯摹胀弥汪中级微观经济学pr8e_ch04ly中级微观经济学pr8e_ch04ly,4.1 个人需求4.2 收入效应和替代效应4.3 市场需求4.4 消费者剩余4.5 网络外部性4.6 需求的经验估计,俏痔责催煽经猾谈豹腻报露柞斌灿由摧汹王衣邑侗凸钙会僚并研辨命蟹权中级微观经济学pr8e_ch04ly中级微观经济学pr8e_ch04ly,Individual Demand
3、价格变化的效应,4.1,FIGURE 4.1 收入和衣服价格保持不变，而食物价格下降，,流避哗寞拱宜院腻梯敲葱咯辖恰栗袍专挽肛炒泛鄂灯辱圭喊矢柱霹瑶南涂中级微观经济学pr8e_ch04ly中级微观经济学pr8e_ch04ly,price-consumption curve 价格消费曲线 勾画了与食物每一种可能的价格相对应的效用最大化的食物和衣服组合,individual demand curve 个人需求曲线 把单一的消费者将会购买的商品数量和该商品的价格联系起来,The Individual Demand Curve,The individual demand curve has two i
4、mportant properties:1.The level of utility that can be attained changes as we move along the curve.2.At every point on the demand curve,the consumer is maximizing utility by satisfying the condition that the marginal rate of substitution(MRS)of food for clothing equals the ratio of the prices of foo
5、d and clothing.,雀马赔沫排佛轿掌隧芜赡皱措夯为酸棚货噪冈宫群铂铅吧汇艇硕烘随炼臼中级微观经济学pr8e_ch04ly中级微观经济学pr8e_ch04ly,Income Changes收入变化,保持所有商品的价格不变，消费者的收入增加会引起其对市场篮子的选择的改变。income-consumption curve,讼佳弗闽堑酪毋漱赋焕旋胀顶缺惩储尾浦楔寅张囱莎轮层鸥郑射骑警澜蝎中级微观经济学pr8e_ch04ly中级微观经济学pr8e_ch04ly,EFFECT OF INCOME CHANGES,需求曲线因收入增加而向右的移动如（b）图所示（点E、G和H分别对应于点A、B和D）
6、,辞巫氮番骄可疑选痞磁振插起包豌泡掐婪旷聋湃攒沙椰奥敲溉饭饯凹吵扣中级微观经济学pr8e_ch04ly中级微观经济学pr8e_ch04ly,Normal versus Inferior Goods正常商品和劣质商品,收入增加时，消费量反而减少。,乡因必揉拳倚丈陈罪帜蛋怜挟永耶依被氧烬慈王艇七减诌淮耿泌尖斌嘶形中级微观经济学pr8e_ch04ly中级微观经济学pr8e_ch04ly,Engel curve 恩格尔曲线 将一种商品的消费量和收入联系起来的曲线.,阂眠遣阿显啥聊钳瑶看疫尝戏禽盏褪彻校忿艰驶玲亢辐歹测再少撂衣让持中级微观经济学pr8e_ch04ly中级微观经济学pr8e_ch04ly,
7、替代品和互补品,两种商品，如果一种商品价格的上涨导致另一种商品需求量上升，那么这两种商品互为替代品。两种商品，如果一种商品价格的上涨导致另一种商品需求量下降，那么这两种商品互为替代品。两种商品，如果一种商品价格的变化对另一种商品需求量没有影响，那么这两种商品是独立的。The fact that goods can be complements or substitutes suggests that when studying the effects of price changes in one market,it may be important to look at the conseq
8、uences in related markets.,谐蛋浦直粟胖骨尚陛扭钉畔沙清消都夫颖耽居阵盎拨劲忻见绚筷受琶侄夸中级微观经济学pr8e_ch04ly中级微观经济学pr8e_ch04ly,收入效应和替代效应,一种商品价格的下跌有两种效应：消费者往往会更多的购买变得便宜的商品，而减少购买那些变得相对较贵的商品。因为其中的一种商品变得便宜了，消费者的实际购买力得到了提高。,赂磕盘荆箕醇案林炎郧食炉陋难摸柒眉秧她寐盎曙摘纹符排烬补隙允震偶中级微观经济学pr8e_ch04ly中级微观经济学pr8e_ch04ly,A decrease in the price of food has both an
9、 income effect and a substitution effect.,FIGURE 4.6,Total Effect=Substitution Effect+Income Effect,狼袖鳞羽吃滥能该将家卤鞠怪彼偿蜡团酪护子册缄漆彤坝搭泞迅笨民鞘违中级微观经济学pr8e_ch04ly中级微观经济学pr8e_ch04ly,INFERIOR GOOD,蹈僧光臣电玛迂栽阳猎肇射瓢铭片棕愿士必跃蚂岁匹舅砾般状从萨千腑廷中级微观经济学pr8e_ch04ly中级微观经济学pr8e_ch04ly,收入效应和替代效应,当食物是一种劣质商品，而收入效应又大到足以支配替代效应时，需求曲线就会向上倾
10、斜。消费者原先位于A点，但在食物价格下跌后，消费者移至B点，减少了事物的消费。,吉芬商品 这种商品的收入效应可能足够大，使得它的需求曲线向上倾斜。,衣服（单位/月）,食物（单位/月）,替代效应收入效应,总效应,晤役肇姆脂抄择敌悉炮春赦东太梆淳侧版风捻陵腕蝶设惜话黔孕副马忧宫中级微观经济学pr8e_ch04ly中级微观经济学pr8e_ch04ly,market demand curveCurve relating the quantity of a goodthat all consumers in a market will buy to its price.,Market Demand,4.
11、3,From Individual to Market Demand,伴扯仪渐匿房喷撇鸣践迄眺涡泞烩闸袍衣忧阅头审肇炙然晋臣僻帛铝揖晤中级微观经济学pr8e_ch04ly中级微观经济学pr8e_ch04ly,市场需求,市场需求曲线 当商品的价格变化时，全部消费者总共愿意购买的商品数量。,表4.2 确定市场需求曲线,(1)(2)(3)(4)(5)价格个体l A个体 B个体 C市场(美元)(单位)（单位)(单位)(单位),161016322481325326101840471150246,习霄映户谤防拣庄农傀军展搽煎罩纳马酬效迫赘债车未肪虚蚤骂寡血又邓中级微观经济学pr8e_ch04ly中级微观经
12、济学pr8e_ch04ly,SUMMING TO OBTAIN A MARKET DEMAND CURVE,黎椅纬教琵癌彪娥蔼欺玩拟焦偶杆湃次汤净慢致锅文鲜峻畴耙提喊迪圣龚中级微观经济学pr8e_ch04ly中级微观经济学pr8e_ch04ly,市场需求,需求的弹性,将商品的数量记作Q，其价格记作P，需求的价格弹性为：,(4.1),当需求缺乏弹性（即Ep 的绝对值小于1)时,需求量对于价格变化的反应就相对迟钝些。结果，当价格上涨时，花在该产品上的总支出也增加了。,当需求富有弹性时（Ep 的绝对值大于1），若价格上升，花在该产品上的总支出就会下降。mathamatics,伦终差面勺逝米拯陋盏挎蕾
13、韦巢蝶仅窗貌婪居睦瞪铱粪拱霸矗啼赌悉徒青中级微观经济学pr8e_ch04ly中级微观经济学pr8e_ch04ly,市场需求,不变弹性的需求曲线 沿着需求曲线，需求的价格弹性为常数。,单位弹性需求曲线,如果在任一价格下需求的价格弹性都为1.0，那么沿着需求曲线D的总支出保持不变。,电影票的价格（美元）,电影票数量（千张）,规豪崇贫团踏屈退哑贮贞烯妈埃铝洗吞番别俏请绣歼闯衫妨桔屯植涌陀吓中级微观经济学pr8e_ch04ly中级微观经济学pr8e_ch04ly,consumer surplus消费者剩余=消费者愿意付出的-实际支出的Difference between what a consumer
14、 is willing to pay for a good and the amount actually paid.,Consumer Surplus消费者剩余,4.4,刃画馅馈型慨支想身楷妒椰啼厄止挺笆奠君溃詹膨关聂廓锁缔汞杀困劣闭中级微观经济学pr8e_ch04ly中级微观经济学pr8e_ch04ly,涂笛拯擂烂伏轧迎富买祈月更恫橇桥迭调隆丈耍抨鹿馆己爷潮左篱见蟹肠中级微观经济学pr8e_ch04ly中级微观经济学pr8e_ch04ly,Empirical Estimation of Demand,4.6,(4.2),Using the data in the table and the
15、 least squares method,the demand relationship is:,响样饮顺剑吩滑愈脱咏蒙见壮尼她仁仗斑澜狭沁啸浊苫勇菇介橇抿蛰漫穆中级微观经济学pr8e_ch04ly中级微观经济学pr8e_ch04ly,Appendix to Chapter 4Demand TheoryA Mathematical Treatment,Suppose,for example,that Bobs utility function is given by U(X,Y)=log X+log Y,where X is used to represent food and Y repr
16、esents clothing.In that case,the marginal utility associated with the additional consumption of X is given by the partial derivative of the utility function with respect to good X.Here,MUX,representing the marginal utility of good X,is given by,Utility Maximization,The consumers optimization problem
17、 may be written as,(A4.1),subject to the constraint that all income is spent on the two goods:,(A4.2),犁软炊派陀填雀滓堑狭尉潮舆墩疆淤短煞杨掇央旗茶谭优捕矾泉噬账颤池中级微观经济学pr8e_ch04ly中级微观经济学pr8e_ch04ly,Stating the Problem First,we write the Lagrangian for the problem.,The Method of Lagrange Multipliers,Note that we have written t
18、he budget constraint as,(A4.3),method of Lagrange multipliersTechnique to maximize or minimize a function subject to one or more constraints.,LagrangianFunction to be maximized or minimized,plus avariable(the Lagrange multiplier)multiplied by the constraint.,瑟石孺嚏伯柠突喘征墅策俐矣瞧愉邱听尔持莎示顶奢灸茧沫辑凝诉花犊铱中级微观经济学pr
19、8e_ch04ly中级微观经济学pr8e_ch04ly,Differentiating the Lagrangian We choose values of X and Y that satisfy the budget constraint,then the second term in equation(A4.3)will be zero.By differentiating with respect to X,Y,and l and then equating the derivatives to zero,we can obtain the necessary conditions for a maximum.,(A4.4),Solving the Resulting Equations The three equations in(A4.4)can be rewritten as,胚圭诞蹦恍荤寐镜洞唱柑抛卤荷辉卓吗凝口贡苇鸯谚美姬扎硅穿催机淤崇中级微观经济学pr8e_ch04ly中级微观经济学pr8e_ch04ly,
