外文翻譯--檸檬市場質(zhì)量不確定和市場機(jī)制

1、<p>　　中文2220字，1440單詞</p><p><b>　　外文原稿一：</b></p><p>　　The Market for “Lemons”: Quality Uncertainty and the Market Mechanism</p><p>　　By George A. Akerlof</p>

2、<p>　　Publication: The Quarterly Journal of Economics, 1970,84 (3)：488-500.</p><p>　　I. Introduction</p><p>　　This paper relates quality and uncertainty. The existence of goods of many grad

3、es poses interesting and important problems for the theory of markets. On the one hand, the interaction of quality differences and uncertainty may explain important institutions of the labor market. On the other hand, th

4、is paper presents a struggling attempt to give structure to the statement: "Business in underdeveloped countries is difficult"; in particular, a structure is given for determining the economic costs of</p>

5、;<p>　　There are many markets in which buyers use some market statistic to judge the quality of prospective purchases. In this case there is incentive for sellers to market poor quality merchandise, since the retu

6、rns for good quality accrue mainly to the entire group whose statistic is affected rather than to the individual seller. As a result there tends to be a reduction in the average quality of goods and also in the size of t

7、he market. It should also be perceived that in these markets social and pr</p><p>　　The automobile market is used as a finger exercise to illustrate and develop these thoughts. It should be emphasized that t

8、his market is chosen for its concreteness and ease in understanding rather than for its importance or realism.</p><p>　　Ⅱ. THE MOBEL WITH AUTOMOBILES AS AN EXAMPLE</p><p>　　A. The Automobiles Ma

9、rket</p><p>　　The example of used cars captures the essence of the problem. From time to time one hears either mention of or surprise at the large price difference between new cars and those which have just

10、left the showroom. The usual lunch table justification for this phenomenon is the pure joy of owning a "new" car. We offer a different explanation. Suppose (for the sake of clarity rather than reality) that the

11、re are just four kinds of cars. There are new cars and used cars. There are good cars and bad car</p><p>　　The individuals in this market buy a new automobile without knowing whether the car they buy will be

12、 good or a lemon. But they do know that with probability q it is a good car and with probability (1-q) it is a lemon; by assumption, q is the proportion of good cars produced and (1-q) is the proportion of lemons. </p

13、><p>　　After owning a specific car, however, for a length of time, the car owner can form a good idea of the quality of this machine; i.e., the owner assigns a new probability to the event that his car is a lem

14、on. This estimate is more accurate than the original estimate. An asymmetry in available information has developed: for the sellers now have more knowledge about the quality of a car than the buyers. But good can and bad

15、 cars must still sell at the same price- since it is impossible for a buyer t</p><p>　　Gresham's law has made a modified reappearance. For most cars traded will be the "lemons," and good cars m

16、ay not be traded at all. The "bad" cars tend to drive out the good (in much the same way that bad money drives out the good). But the analogy with Gresham's law is not quite complete: bad cars drive out the

17、 good because they sell at the same price as good can; similarly, bad money drives out good because the exchange rate is even. But the bad cars sell at the same price as good cars since it</p><p>　　B. Asymme

18、trical Information</p><p>　　It has been seen that the good cars may be driven out of the market by the lemons. But in a more continuous case with different grades of goods, even worse pathologies can exist.

19、For it is quite possible to have the bad driving out the not-so-bad driving out the medium driving out the not-so-good driving out the good in such a sequence of events that no market exists at all.</p><p>　

20、　One can assume that the demand for used automobiles depends most strongly upon two variables --the price of the automobile p and the average quality of used cars traded,μ, or Q d = D (p, μ). Both the supply of used cars

21、 and also the average qualityμwill depend upon the price, or μ=μ (p) and S= S (p). And in equilibrium the supply must equal the demand for the given average quality, or S (p) =D (p, μ (p)). As the price falls, normally t

22、he quality will also fall. And it is quite possible that no g</p><p>　　Such an example can be derived from utility theory. Assume that there are just two groups of traders: groups one and two. Give group one

23、 a utility function.</p><p>　　Where M, is the consumption of goods other than automobiles, xi, is the quality of the ith automobile, and n is the number of automobiles. </p><p>　　Similarly, let&

24、lt;/p><p>　　Where M, xi ,and n are defined as before.</p><p>　　Three comments should be made about these utility functions: (1) without linear utility (say with logarithmic utility) one gets needle

25、ssly mired in algebraic complication. (2) The use of linear utility allows a focus on the effects of asymmetry of information; with a concave utility function we would have to deal jointly with the usual risk-variance ef

26、fects of uncertainty and the special effects we wish to discuss here. (3) U1 and U2 have the odd characteristic that the addition of a second car,</p><p>　　To continue, it is assumed (1) that both type one t

27、raders and type two traders are von Neumann-Morgenstern maximizers of expected utility; (2) that group one has N cars with uniformly distributed quality x, 0≤x≤2 , and group two has no cars; (3) that the price of "o

28、ther goods" M is unity. </p><p>　　Denote the income (including that derived from the sale of automobiles) of all type one traders as Y1 and the income of all type two traders as Y2. The demand for used

29、cars will be the sum of the demands by both groups. When one ignores indivisibilities, the demand for automobiles by type one traders will be</p><p>　　Dl = Y1/P μ/P >1</p>

30、;<p>　　Dl =0 μ/P <1.</p><p>　　And the supply of cars offered by type one traders is</p><p>　　(1) S 2 = p N /2 p ≤ 2</p>

31、;<p>　　with average quality</p><p>　　(2) μ= P/2.</p><p>　　(To derive (1) and (2), the uniform distribution of automobile quality is used.)</p><p>　　Similarly the demand of

32、type two traders is</p><p>　　D2 = Y2/P 3μ/ 2>P</p><p>　　D2 =0 3μ/ 2<P</p><p><b>　　and</b></p><p&g

33、t;<b>　　S2=0.</b></p><p>　　Thus total demand D (p, μ) is</p><p>　　D (P, μ) = (Y2+Y1)/p if p<μ</p><p>　　D (P, μ) =Y2/p if μ< p

34、 < 3μ/ 2</p><p>　　D (P, μ) =0 if p> 3μ/2.</p><p>　　However, with price p, average quality is p/2 and therefore at no price will any trade take place at all: in spi

35、te of the fact that at any given price between 0 and 3 there are traders of type one who are willing to sell their automobiles at a price which traders of type two are willing to pay. </p><p><b>　　譯文一：

36、</b></p><p>　　檸檬市場：質(zhì)量不確定和市場機(jī)制</p><p>　　George A. Akerlof</p><p><b>　　一、引 言</b></p><p>　　本文論述的是質(zhì)量和不確定性問題。多種檔次的物品給市場理論提出了有趣而又重要的問題。一方面，質(zhì)量差異和不確定性的相互作用可以解

37、釋某些重要的勞動市場制度。另一方面，本文力求對“在不發(fā)達(dá)國家做生意是因難的”給出一個模型，尤其是要給出一個用于確定不誠實(shí)的經(jīng)濟(jì)成本的模型。其它理論的應(yīng)用還包括對貨幣市場結(jié)構(gòu)、不可保險(xiǎn)性、耐用品的流動性以及品牌產(chǎn)品的評論。</p><p>　　在許多市場中，購買者總是利用某些市場統(tǒng)計(jì)數(shù)據(jù)來判斷欲購商品的質(zhì)量。在這種情況下，銷售者就有動機(jī)銷售劣質(zhì)商品，因?yàn)閺膬?yōu)質(zhì)商品中受益的主要是那些統(tǒng)計(jì)數(shù)據(jù)受影響的銷售者整體而不是單

38、個銷售者。結(jié)果是，產(chǎn)品的平均質(zhì)量往往會下降，市場規(guī)模相對縮小。還應(yīng)該看到的是，在這些市場中，社會收益和私人收益是有差別的，因此，在某些情況下，政府干預(yù)可以增加各方的福利?；蛘呤?，私人制度可能會產(chǎn)生，以利用各方潛在的福利增長。但是，這些制度并不是孤立分散的。因此，權(quán)力的集中也就有可能形成——這就是制度本身帶來的不良后果。</p><p>　　本文試圖用汽車市場來闡述上述思想。應(yīng)該強(qiáng)調(diào)的是，之所以選擇汽車市場，是因?yàn)?/p>

39、它非常具體并且易于理解，而不是因?yàn)樗闹匾曰颥F(xiàn)實(shí)性。</p><p>　　二、以汽車為例的模型</p><p><b>　　1．汽車市場</b></p><p>　　舊車市場的例子說明了問題的本質(zhì)。用以解釋這種現(xiàn)象的常見理由是，擁有一輛新車可以帶來快樂，而我們卻給出了另一種解釋。假定(為了說明問題，而不是現(xiàn)實(shí)情況)市場中只有4種汽車，即新車和

40、舊車，好車和次品車(在美國，也稱之為“檸檬”)。新車有可能是好車，也有可能是次品車；當(dāng)然，舊車也是如此。 </p><p>　　人們在上述市場中購買一輛新車時，并不知道他所購買的汽車是好車還是次品車。但是，假定在生產(chǎn)出來的汽車中．好車的比例為q，次品車的比例為1-q。則買主必定知道買到好車的概率為q．買到次品車的概率為1-q。</p><p>　　而在對某輛汽車擁有一段時間后，車主就可以了

41、解該車的質(zhì)量，也就是說，車主會重新估計(jì)其汽車的概率是次品車，這一估計(jì)要比原來的估計(jì)更準(zhǔn)確。這就形成了一種可得信息的不對稱：現(xiàn)在賣主比買主更了解汽車的質(zhì)量。但是，好車和次品車仍然以相同的價(jià)格出售——因?yàn)橘I主不能區(qū)別好車和次品車。顯然，舊車與新車的價(jià)值不會一樣——如果舊車的價(jià)值和新車的一樣，那么，在好車的概率更高、次品車的概率更低的情況下，以新車的價(jià)格出售一輛次品車，然后買回一輛新車肯定是有利可圖的。因此，好車的車主被鎖定了。實(shí)際上，他不僅

42、得不到其汽車的真實(shí)價(jià)值，而且也得不到新車的預(yù)期價(jià)值。</p><p>　　格雷欣法則以另一種方式出現(xiàn)了。絕大多數(shù)出售的汽車可能是次品車，好車的買賣可能也根本不存在。次品車傾向于將好車擠出市場(這與劣幣驅(qū)逐良幣極其相依)。但是，與格雷欣法則不盡相同的是，次品車擠掉好車的原因在于它們的售價(jià)與好車的售價(jià)一樣。類似地，劣幣驅(qū)逐良幣的原因是這兩種貨幣的交換率是一樣的。但是，次品車的售價(jià)與好車的售價(jià)一樣是因?yàn)橘I主不能區(qū)分好車

43、和次品車，然而在格雷欣法則中，買主和賣主部有可能可以區(qū)分劣幣和良幣。因此，上述兩種情況極其相像，但并不完全相同。 </p><p><b>　　2．不對稱信息 </b></p><p>　　由上面的分析可以看出，好車有可能將次品車擠出市場。但是，在存在不同檔次商品的連續(xù)市場中，更糟糕的異?，F(xiàn)象也會出現(xiàn)。其中就有可能是，次品格不太差的產(chǎn)品擠出市場，不太差的產(chǎn)品又將中檔產(chǎn)

44、品擠出市場，中檔產(chǎn)品則將不太好的產(chǎn)品擠出市場，不太好的產(chǎn)品格高檔產(chǎn)品擠出市場，依次類推，最終不會有任何市場存在。</p><p>　　可以假定，如果對舊車的需求嚴(yán)格地取決于兩個變量——汽車的價(jià)格p和舊車的平均質(zhì)量μ，則舊車的需求函數(shù)可以表述如下：Qd =D (p，μ)。舊車的供給和平均質(zhì)量μ將取決于價(jià)格，也即μ＝μ(p),S=S(p)。在均衡狀態(tài)中，給定舊車的平均質(zhì)量，則其供給必定等于需求，即S (P)＝D(p，

45、μ(P))。如果價(jià)格下降，平均質(zhì)量通常也將下降。很有可能在任何價(jià)格水平廠，那個會有物品買賣。 </p><p>　　上述例子可以從效用理論中推導(dǎo)出來。假定只有兩組交易商，組1和組2。讓組1的效用函數(shù)為：</p><p>　　式中，M表示除汽車以外的其他消費(fèi)品，xi表示i 輛汽車的質(zhì)量，n表示汽車的數(shù)量。</p><p>　　同樣地，讓組2的效用函數(shù)為：</p&

46、gt;<p>　　式中的M、xi和n的含義與上式相同。</p><p>　　對這些效用函數(shù)還要提三點(diǎn)：1、沒有了線性效用（即沒有對數(shù)效用），人們會陷入不必要的代數(shù)并發(fā)癥。2、線性工具的使用，允許對信息不對稱帶來的影響。在一個凹效用函數(shù)下，我們需要處理不確定的風(fēng)險(xiǎn)方差，以及我們在這里討論的特殊效用。3、U1 和U2 具有奇數(shù)特征，也就是說第二部車的加入，將帶來同等的效用?，F(xiàn)實(shí)是，這些犧牲可以避免正確

47、焦點(diǎn)的轉(zhuǎn)移。</p><p>　　接下來，我們假設(shè)：1、第一類和第二類交易商都達(dá)到了馮諾伊曼、摩根斯坦的預(yù)期效用最大化；2、組一擁有N輛質(zhì)量分布均勻的汽車x，0≤x≤2，組二沒有車；3、其它商品的價(jià)格M是統(tǒng)一的。</p><p>　　將單個交易商組合的所有收入（包括來自汽車銷售的收入）記作Y1 ，兩個汽車交易商組合的收入記作Y2 。汽車使用的需求將是這兩組需求的總和。當(dāng)其中一組忽略了個體，

48、那么組一的汽車需求則如下：</p><p>　　Dl = Y1/P ，μ/P >1；Dl =0，μ/P <1.</p><p>　　而組一所能提供的汽車供應(yīng)將是：</p><p>　　S 2 = p N /2，p ≤ 2，這里汽車的質(zhì)量都是一樣的 （1）</p><p>　　μ= P/2

49、 （2）</p><p>　　公式（1）和公式（2）就派生出了對汽車質(zhì)量均勻分布的使用。</p><p>　　同樣的，組二的公式是：</p><p>　　D2 = Y2/P ， 3μ/ 2>P</p><p>　　D2 =0 ， 3μ/ 2<P</p><p><b&g

50、t;　　以及S2=0.</b></p><p>　　因此總需求D (p, μ)就是：</p><p>　　D(P,μ) = (Y2+Y1)/p ，p<μ</p><p>　　D(P,μ) =Y2/p ， μ< p < 3μ/ 2</p><p>　　D(P,μ) =0 ，if p> 3μ/2.</p