經(jīng)濟學(xué)中級微觀經(jīng)濟學(xué)講義15章課件

1、第1章 市場1、經(jīng)濟學(xué)的概念與方法建立模型：經(jīng)濟學(xué)的研究是通過對社會各種現(xiàn)象建立模型來進行的。通過一個模型可以簡單地表示現(xiàn)實世界的情況。變量設(shè)計與因果關(guān)聯(lián)、對問題的簡化構(gòu)建經(jīng)濟模型的五個步驟A 界定問題及其范圍（Definition of the Problem）B 形成假說 （Formulation of Hypotheses）C 根據(jù)假說對現(xiàn)實做出解釋 （Explanation）D 對經(jīng)濟模型進行檢驗 （Verification）E 根據(jù)檢驗結(jié)果放棄、修改或者接受模型 （Conclusion）最優(yōu)化與均衡每當(dāng)我們試圖分析人類的行為時，我們需要一種分析的基礎(chǔ)框架，這個基礎(chǔ)框架建立在以下兩個簡

2、單原理的基礎(chǔ)上：最優(yōu)化：人們總是選擇他們能支付得起的最佳消費方式（廠商總是選擇成本最低的生產(chǎn)方式）。均衡原理：價格會自動調(diào)整，直到人們的需求數(shù)量與供給數(shù)量相等。2、需求曲線：收入水平約束下消費者為某一數(shù)量的消費水平愿意支付的最高價格。這個價格我們也稱其為保留價格。（Reservation Price）QP需求的區(qū)域0或者說需求曲線顯示的是在非價格因素保持不變的情況下，每單位產(chǎn)品售價發(fā)生的變化導(dǎo)致他愿意購買的數(shù)量的變化（價格數(shù)量關(guān)系）；它與價格成反向相關(guān)關(guān)系。非價格的需求決定因素包括：收入消費者偏好相關(guān)商品價格（互補品、替代品） 3、供給曲線：生產(chǎn)者在成本約束下提供特定數(shù)量的產(chǎn)品所能接受的最低價

3、格。供給的區(qū)域短期的特例：土地或住房供給一般化的供給線4.市場均衡：均衡價格與均衡數(shù)量的決定sLssDP*市場調(diào)節(jié)（價格機制） 當(dāng)PPe時，QdQs，市場出現(xiàn)超額供給，消費者主導(dǎo)，買方市場. P自動下降，過剩逐漸減小，直至均衡； 當(dāng)PQs，市場出現(xiàn)超額需求，供給者主導(dǎo)，賣方市場. P自動上升，短缺逐漸減小，直至均衡。市場均衡的變動 當(dāng)需求曲線和供給曲線移動時，均衡價格和均衡產(chǎn)量都會發(fā)生變動。 分析均衡變動的三個步驟： （1）確定該變動是需求曲線還是供給曲線； （2）確定曲線移動的方向； （3）用供求圖說明均衡變動的影響。比較靜態(tài)分析SDS1可交易領(lǐng)域擴大可交易的領(lǐng)域比較靜態(tài)分析SDS1可交易領(lǐng)

4、域擴大可交易的領(lǐng)域可交易領(lǐng)域的進一步擴大不完全競爭的市場完全（差別）壟斷的狀態(tài)：廠商將商品按照不同的價格分別賣給不同的消費者，最終的商品交易量正好與完全競爭市場完成的交易量是相同的，只是生產(chǎn)者剝奪了所有的消費者剩余。P*P1P2差別壟斷者：短期供給情況下的均衡(S曲線垂直)QP0差別壟斷市場的交易過程：長期供給一般壟斷者：交易的數(shù)量會低于完全競爭市場的交易量，存在廠商對消費者剩余的剝奪。QP0一般壟斷市場的交易過程：壟斷者按照相同的價格出售產(chǎn)品P0Q0Q1P1An Illustration: Modeling the Apartment MarketPurpose: How are apart

5、ment rents determined? Are rents “desirable”?Simplifying assumptions: apartments are close or distant, but otherwise identicaldistant apartments rents are exogenous (外生變量） and knownmany potential renters and landlordsTwo Very Common Modeling AssumptionsRational Choice (理性選擇）: Each person tries to ch

6、oose the best alternative available to him or her.Equilibrium （均衡）: economic agents interact with each other, resulting in an equilibrium, in which each person reaches an optimal decision given others decisions.Modeling Apartment DemandDemand: Suppose the most any one person is willing to pay to ren

7、t a close apartment is $500/month. Thenp = $500 QD = 1.Suppose the price has to drop to $490 before a 2nd person would rent. Then p = $490 QD = 2.Modeling Apartment DemandThe lower is the rental rate p, the larger is the quantity of close apartments demandedp QD .The quantity demanded vs. price grap

8、h is the market demand curve for close apartments.Market Demand Curve for ApartmentspQDModeling Apartment SupplySupply: It takes time to build more close apartments, so in this short-run the quantity available is fixed (at say 100).Market Supply Curve for ApartmentspQS100Competitive Market Equilibri

9、um(競爭性市場均衡）Quantity demanded = quantity available price will neither rise nor fallso the market is at a competitive equilibrium.Competitive Market EquilibriumpQD,QSpe100People willing to pay pe for close apartments get closeapartments.People not willing to pay pe for close apartments get distant apa

10、rtments.Comparative Statics（比較靜態(tài)分析）What is exogenous in the model?price of distant apartmentsquantity of close apartmentsincomes of potential renters.What happens if these exogenous variables change?Note： We are not analyzing the transition process or dynamic process.Comparative StaticsSuppose the p

11、rice of distant apartment rises.Demand for close apartments increases (rightward shift), causing a higher price for close apartments.Market EquilibriumpQD,QSpe100Higher demand causes highermarket price; same quantitytraded.More Comparative Statics (Do Them Yourself)Suppose there were more close apar

12、tments.Or, renters income rises;Elaboration of the Basic Model: Taxation Policy AnalysisLocal government taxes apartment owners.What happens topricequantity of close apartments rented?Is any of the tax “passed” to renters?Taxation Policy AnalysisMarket supply is unaffected.Market demand is unaffecte

13、d.So the competitive market equilibrium is unaffected by the tax.Price and the quantity of close apartments rented are not changed.Landlords pay all of the tax.Imperfectly Competitive MarketCase 1： A Monopolistic LandlordLandlord sets a rental price p he rents D(p) apartments.Revenue = pD(p).He choo

14、ses p to maximizes p D(p), subject to D(p) S (total number of apartments in his hands)Typically, his optimal p is such thatD(p) S, that is, there are vacant apartments.Monopolistic Market EquilibriumpQD,QSMiddlepriceMiddle price, medium quantitydemanded, larger revenue.Monopolist does not rent all t

15、heclose apartments.100Vacant close apartments.Imperfectly Competitive Market Case 2： Perfectly Discriminatory Monopolistic LandlordImagine the monopolist knew willingness-to-pay of everybody,Charge $500 to the most willing-to-pay,charge $490 to the 2nd most willing-to-pay, etc.Discriminatory Monopol

16、istic Market EquilibriumpQD,QS100p1 =$5001Discriminatory Monopolistic Market EquilibriumpQD,QS100p1 =$500p2 =$49012Discriminatory Monopolistic Market EquilibriumpQD,QS100p1 =$500p2 =$49012p3 =$4753Discriminatory Monopolistic Market EquilibriumpQD,QS100p1 =$500p2 =$49012p3 =$4753Discriminatory Monopo

17、listic Market EquilibriumpQD,QS100p1 =$500p2 =$49012p3 =$4753peDiscriminatory monopolistcharges the competitive marketprice to the last renter, andrents the competitive quantityof close apartments.Rent Control(房租管制）Local government imposes a maximum legal price, pmax pe, the competitive price.Market

18、 EquilibriumpQD,QSpe100pmaxExcess demandThe 100 close apartments areno longer allocated bywillingness-to-pay (lottery, lines,large families first?).Value Judgement（價值判斷）Which of the following is better?Rent controlPerfect competitionMonopolyDiscriminatory monopolyBut, what do you mean by “better”?Pa

19、reto Efficiency（帕累托效率）Vilfredo ParetoA Pareto outcome allows no “wasted welfare”;i.e. the only way one persons welfare can be improved is to lower another persons welfare. Pareto EfficiencyA Pareto inefficient outcome means there remain unrealized mutual gains-to-trade.Any market outcome that achiev

20、es all possible gains-to-trade must be Pareto efficient.Pareto EfficiencyCompetitive equilibrium:all close apartment renters value them at the market price pe or moreall others value close apartments at less than peso no mutually beneficial trades remainso the outcome is Pareto efficient.Pareto Effi

21、ciencyDiscriminatory Monopoly:assignment of apartments is the same as with the perfectly competitive marketso the discriminatory monopoly outcome is also Pareto efficient.Pareto EfficiencyMonopoly:not all apartments are occupiedso a distant apartment renter could be assigned a close apartment and ha

22、ve higher welfare without lowering anybody elses welfare.so the monopoly outcome is Pareto inefficient.Pareto EfficiencyRent Control:some close apartments are assigned to renters valuing them at below the competitive price pesome renters valuing a close apartment above pe dont get close apartmentsPa

23、reto inefficient outcome.不同市場機制的效率比較：帕雷托最優(yōu)完全競爭市場和差別壟斷市場是帕雷托最優(yōu)的，區(qū)別只在于收入分配的不同，差別壟斷市場導(dǎo)致生產(chǎn)者剝奪消費者剩余。但是帕雷托最優(yōu)與分配問題無關(guān)，只與交換的的效率有關(guān)。第2章 預(yù)算約束從本章開始研究消費者行為理論消費者行為研究的三個步驟：消費者偏好預(yù)算約束結(jié)合二者確定消費者選擇 預(yù)算約束：兩種商品（x1,x2）（消費束），兩種價格（p1,p2），確定性收入（m）。我們把當(dāng)價格為（p1,p2）收入為m時，消費者能負(fù)擔(dān)的消費束稱為消費者的預(yù)算集。預(yù)算集的性質(zhì)預(yù)算線：預(yù)算線指的是成本正好等于m的一系列商品束，這些商品束的費用正

24、好可以把消費者的收入用完。x1x2M/p1M/p2預(yù)算線：斜率為-p1/p2預(yù)算集預(yù)算線的斜率正好等于兩種物品的邊際替代率。預(yù)算線的變動：收入變動和價格變動的影響。收入變動使預(yù)算線平移；價格變動使預(yù)算線旋轉(zhuǎn)。x1x2M/p1M/p2預(yù)算線：斜率為-p1/p2預(yù)算集增加的預(yù)算集收入增加導(dǎo)致的預(yù)算線移動M/p1M/p2x1x2M/p1M/p2預(yù)算線：斜率為-p1/p2預(yù)算集商品x1價格降低和提高產(chǎn)生的預(yù)算線轉(zhuǎn)動稅收、補貼和配給產(chǎn)生的對預(yù)算線的影響從量稅（p+t）和從價稅(1+t)p從量補貼(p-s)和從價補貼(1-s)p對消費者而言，此類稅收是提高了價格，而補貼是降低了價格。導(dǎo)致預(yù)算線旋轉(zhuǎn)。總額稅

25、或總額補貼總額稅或總額補貼使消費者收入發(fā)生變化,導(dǎo)致預(yù)算線平行移動。x1x2M/p1M/p2預(yù)算線：斜率為-p1/p2預(yù)算集x11受配給限制的預(yù)算集政府配給供應(yīng)x1x2M/p1M/p2預(yù)算線：斜率為-p1/p2預(yù)算集斜率為-(p1+t)/p2x11對大于x11的消費量征稅作業(yè)：1、假定你的收入為40美元，用于兩種物品的消費，物品1的價格為10美分，物品2的價格為5美分。a、寫出預(yù)算方程；劃出預(yù)算線；b、假定物品1價格降為5美分，寫出新預(yù)算方程，劃出新預(yù)算線。c假定收入降為30美元，兩種物品價格不變，為5美分，寫出預(yù)算方程并劃出預(yù)算線。d在你的圖形中，劃出c情況下你能支付得起而在a情況下不能支付

26、得起的消費束組合；e劃出在a情況下能支付得起在c情況下不能支付得起的消費組合。2、你的預(yù)算狀態(tài)表現(xiàn)為你能夠消費4單位x和6單位y，或者12單位x和2單位y。劃出預(yù)算線；x和y的價格比為多少；如果x的價格為1，寫出上述預(yù)算線的預(yù)算方程；如果x的價格為3，寫出上述預(yù)算線的預(yù)算方程。3、如果你消費100單位x和50單位的y，x的價格從2提高到3，y的價格保持為4。你的收入需要增加多少，才能繼續(xù)負(fù)擔(dān)的起100單位的x和50單位y的消費？3 偏好偏好：消費者對不同消費束的喜愛程度。嚴(yán)格偏好：弱偏好：無差異：關(guān)于偏好的假設(shè)完備性公理：任何兩個消費束都是可以比較的反身性公理：任何消費束假定與自身一樣好傳遞性

27、公理：如果A大于B，B大于C，則A大于C。無差異曲線不能相交x1x2x2x1完全替代品：消費者愿意按照固定比率用一種商品替代另一種商品.x2x1x1x2x2x1完全互補品：始終以固定比例一起消費的商品.x1x2xyy為厭惡品：如果消費更多的厭惡品必須消費更多的非厭惡品作為補償才能保持總效用不變，因此其斜率為正。yxy為中性商品，消費者對其持中立態(tài)度饜足點：最佳消費束xy離散商品XY12單調(diào)性偏好及凸性特征較好消費束較差消費束ABCC點為A、B兩點的平均消費束，落在右邊的無差異線上斜率為負(fù)及凸?fàn)钐卣靼紶钇肁BC邊際替代率MRS：無差異曲線的斜率就是兩種物品的邊際替代率。邊際替代率衡量消費者愿意

28、用一種商品去替代另一種商品的比率。邊際替代率變動規(guī)律：邊際替代率遞減。斜率為-E，為了使消費者保持在A點不動，E應(yīng)該是多少？Axy按照交換率E交換與邊際替代率A點的邊際替代率按照任何交換率而不是邊際替代率，消費者總想用一種物品交換另一種物品，但是如果交換率等于邊際替代率，消費者會保持不動效用效用函數(shù)：為每一個可能的消費束指派一個數(shù)字，使得指派給受較多偏好的消費束的數(shù)字大于指派給受較少偏好的消費束的數(shù)字的方法。如果對消費束（x1,x2）的偏好超過對于（y1,y2）消費束的偏好，其充分必要條件是（x1,x2）的效用大于（y1,y2）的效用。即（x1,x2） （y1,y2），當(dāng)且僅當(dāng) u（x1,x2

29、）u（y1,y2）。效用指派的唯一重要特征在于它對商品束所進行的排列。效用函數(shù)的數(shù)值只在對不同商品束進行排列時才有意義。任何兩個商品束之間的效用差額的大小是無關(guān)重要的。因為這種效用強調(diào)商品束的排列次序，所以它被稱為序數(shù)效用。商品束效用1效用2效用3A168-1B62-2C41-3指派效用的不同辦法指派效用函數(shù)的不同方法也可以通過對特定排序狀態(tài)的效用函數(shù)進行正單調(diào)變換的方式獲得。通常我們把一個數(shù)u變換成其他某個數(shù)字的函數(shù)f(u)來表示一個單調(diào)變換。因此如果u1u2，則f(u1) f(u2)。乘以一個正數(shù)，加上任意數(shù)或者數(shù)字的奇次冪等等，都是單調(diào)變換的例子。一個效用函數(shù)的單調(diào)變換還是一個效用函數(shù)，

30、這個效用函數(shù)代表的偏好與原效用函數(shù)代表的偏好相同。vABuV=f(u)V=f(u)A圖所表示的是一個單調(diào)函數(shù)始終遞增的函數(shù)B圖表示的函數(shù)不是單調(diào)函數(shù)，它有時遞增，有時遞減基數(shù)效用:假定效用象高度和重量一樣是可以度量的，而且效用的度量是按照基數(shù)順序排列的.基數(shù)效用并不是描述選擇行為所必須的,而且也沒有令人信服的方法來指派基數(shù)效用,所以序數(shù)效用分析框架的出現(xiàn)取代了基數(shù)效用.基數(shù)效用理論幾個效用函數(shù)的例子假設(shè)效用函數(shù)為：U(x1,x2)=x1 x2，怎樣做出無差異曲線？u1u2u3x1x2描述完全替代偏好的效用函數(shù)：U(x1,x2)=ax1 +bx2描述完全互補偏好的效用函數(shù)：U(x1,x2)=Minax1 ，bx2擬線性偏好U(x1,x2)=v(x1 )+x2擬線性偏好柯布-道格拉斯偏好U(x1,x2)=