西方经济学教科书中关于柠檬市场会萎缩的分析及结论是错误的

宋圭武

“柠檬”在美国俚语中表示“次品”或“不中用的东西”所以，柠檬市场也称次品市场。1970年，31岁的著名经济学家乔治·阿克洛夫发表了《柠檬市场：质量不确定和市场机制》的论文，对柠檬市场进行了具体分析，所以，柠檬市场也称阿克洛夫模型。乔治·阿克洛夫、迈克尔·斯彭斯、约瑟夫·斯蒂格利茨等三人，因为在不对称信息上的研究，共同获得2001年的诺贝尔经济学奖。

在《柠檬市场：质量不确定和市场机制》这篇论文中，作者认为，在信息不对称下，由于柠檬市场中的价格过低，价格机制将驱使拥有好车的卖方离开市场，形成逆向选择。最终造成市场中充满劣质品，使市场崩溃或萎缩。其分析的思路是：柠檬市场由于交易一方并不知道商品的真正价值，只能通过市场上的平均价值来判断平均质量，由于难以分清商品好坏，因此也只愿意付出平均价格。由于商品有好有坏，对于平均价格来说，提供好商品的自然就要吃亏，提供坏商品的便得益，于是好商品便会逐步退出市场。由此导致市场商品平均质量下降，于是平均价格也会进一步下降，最后市场就只剩下坏商品。

这里柠檬市场也就是我们常说的旧货市场或二手市场，其中旧货地摊市场，即跳蚤市场也属于柠檬市场一类。

对于上述旧货市场或二手市场会崩溃或萎缩的推理分析思路，已成为西方经济学教科书中的一个经典分析，其结论也成为了西方经济学教科书的一个基本原理。个人认为，关于柠檬市场会崩溃或萎缩的观点是错误的，其分析推理也是错误的，是与现实不符的，其结论不应成为西方经济学的一个基本原理。下面谈谈理由。

第一，新货市场与旧货市场都存在信息不对称问题，而且有时候新货市场信息不对称问题更严重，尤其是对于刚开发出的新产品，消费者对其认知更少。所以，按作者基于信息不对称的分析推理，同样也适用于新货市场，这会推出新货市场也会崩溃或萎缩，这与现实是矛盾的。

第二，在现实中，旧货市场或二手市场不仅没有崩溃或萎缩，而且有时候需求更旺盛，这也间接证明作者的推理应是错误的。

第三，用平均价值分析市场价格形成的思路是不符合实际情况的。在旧货市场上，消费者出价并非按平均价值出价，市场价格的形成在许多情况下往往是供给方和需求方根据不同类商品和同一类商品不同质量等级的实际情况一对一讨价还价的结果。这里在旧货市场上供给方与需求方讨价还价的过程与新货市场上供给方与需求方讨价还价的过程本质是一样的。另外，在实际市场交易中，消费者如何估算平均价值，其答案并不十分明确。在这种情况下，消费者按平均价值出价的前提就难以成立，其分析过程及结论自然也就缺乏逻辑可靠性。

第四，对低收入者而言，旧货市场是一个值得去的地方。因为旧货市场往往商品价格更便宜，东西更实惠。一般社会低收入人口越多，对旧货市场需求越大。

第五，在信息不对称较为严重的情况下，在旧货市场上，一些高质量的商品其市场交易期限可能会拉长，并不一定会退出市场。一般情况是，对于高质量的商品，人们是不会轻易以低价就销售出去的，其交易期限可能会拉长。好货总是等待识货者。当然，在一些特殊情况下，也有例外。比如，若供给方急需资金周转，高质量的商品就可能会低价销售，交易期限会缩短。

第六，旧货市场的商品，不管是高质量，还是低质量，其退出市场的积极性都很低。因为旧货市场的商品，不管是高质量，还是低质量，对供给方而言，都是属于效用较低的商品，或属于多余的商品，因为若一件商品对供给方效用还较高，或还有较大使用价值，供给方是不可能低价处理的。所以，在旧货市场，不管是高质量商品，还是低质量商品，其退出旧货市场的积极性都很低。

第七，在旧货市场，相比低质量商品，高质量商品退出市场的可能性更小。因为对需求者而言，一些高质量商品性价比更好，对其需求必然更大，或者要比低质量商品需求更大。在这种情况下，倒是低质量商品被市场淘汰的可能性更大，其退出市场的可能性也更大。

上述观点和看法供大家参考商榷。不妥之处，请各位朋友指正。（作者：中共甘肃省委党校〔甘肃行政学院〕决策咨询部副主任、二级教授）

The analysis and conclusion about the shrinking of the lemon market in the western economics textbook is wrong

"Lemon" in American slang means "defective" or "useless things". Therefore, the lemon market is also called the defective market. In 1970, the famous economist George Akerlof, aged 31, published the paper "The Lemon Market: Quality Uncertainty and Market Mechanism", which made a specific analysis of the lemon market. Therefore, the lemon market is also called the Akerlof model. George Akerlof, Michael Spence and Joseph Stiglitz, because of their research on asymmetric information, jointly won the Nobel Prize in Economics in 2001. In the paper "The Lemon Market: Quality Uncertainty and Market Mechanism", the author believes that under the condition of information asymmetry, because the price in the lemon market is too low, the price mechanism will drive the seller with a good car to leave the market, forming adverse selection. Eventually, the market is full of inferior products, making the market collapse or shrink. The analysis of the idea is: the lemon market because the trading side does not know the true value of the goods, can only judge the average quality through the average value in the market. Because it is difficult to distinguish the goods, they are only willing to pay the average price. Because the goods are good and bad, for the average price, the goods will lose, and the bad goods will benefit, so the goods will gradually withdraw from the market. This leads to the decline of the average quality of market goods, so the average price will also further decline, and finally the market will only be bad goods. Here the lemon market is what we often say the second-hand market or second-hand market, where the second-hand street market, namely the flea market, also belongs to the lemon market. The reasoning analysis of the above second-hand market or second-hand market will collapse or shrink has become a classic analysis in the western economics textbooks, and its conclusion has become a basic principle of the western economics textbooks. Personally, the viewpoint that the lemon market will collapse or shrink is wrong, and its analysis and reasoning are also wrong, which is inconsistent with reality, and its conclusion should not become a basic principle of western economics. Here are the reasons. First, there is information asymmetry in both the new market and the second-hand market, and sometimes the information asymmetry problem in the new market is more serious, especially for the new product that has just been developed, the consumer has less awareness of it. Therefore, according to the author's analysis and reasoning based on information asymmetry, it is also applicable to the new market, which will lead to the new market will collapse or shrink, which is contradictory to reality. Second, in reality, the second-hand market or used market not only did not collapse or shrink, but sometimes the demand is more exuberant, which indirectly proves that the author's reasoning should be wrong. Third, the idea of using average value to analyze the formation of market price is not in line with the actual situation. In the second-hand market, consumers do not bid according to the average value. In many cases, the formation of market price is often the result of one-to-one bargaining between supply and demand according to the actual situation of different categories of goods and different quality levels of the same kind of goods. Here, the process of bargaining between supply and demand in the second-hand market is essentially the same as that in the new market. In addition, in the actual market transaction, the answer to how consumers estimate the average value is not very clear. In this case, the premise that consumers bid according to the average value is difficult to establish, and its analysis process and conclusion naturally lack logical reliability. Fourth, for low-income people, the second-hand market is a place worth going to. Because the second-hand market is often cheaper and more affordable. The more low-income people in general society, the greater the demand for the second-hand market. Fifth, in the case of serious information asymmetry, in the second-hand market, some high-quality products may have a long market transaction term and may not necessarily exit the market. Generally speaking, for high-quality goods, people will not easily sell them at a low price, and their transaction term may be extended. Goods always wait for those who can recognize them. Of course, there are exceptions in some special cases. For example, if the supplier is in urgent need of capital turnover, high-quality products may be sold at a low price, and the transaction term will be shortened. Sixth, the goods in the second-hand market, whether high-quality or low-quality, have a low enthusiasm to exit the market. Because the goods in the second-hand market, whether high-quality or low-quality, are goods with low utility or surplus goods for the supplier, because if a good has a high utility or a large use value for the supplier, the supplier is unlikely to deal with it at a low price. Therefore, in the second-hand market, whether high-quality goods or low-quality goods, they have a low enthusiasm to exit the market. Seventh, in the second-hand market, compared with low-quality goods, high-quality goods are less likely to exit the market. Because for the demander, some high-quality goods are more cost-effective, which will lead to greater demand for them, or greater demand than low-quality goods. In this case, it is the low-quality goods are more likely to be eliminated by the market, and the possibility of their exit from the market is greater. The above views and opinions are for your reference. Where there is anything wrong, please correct me.