求解一道关于逆向选择的微经题目

Let us consider a situation that a market of used cars consists of two qualities, good and bad, of commodities. Consumers of used cars value good used cars at 600 thousand yen and 300 thousand yen for bad ones. They cannot distinguish the quality of any given car. In contrast, retailers of the cars value good used cars at 450 thousand yen and 200 thousand yen for bad ones, and they can distinguish the qualities. Suppose that the distribution over good cars and bad ones is (μ, 1 − μ). Answer the following questions.
(1) When μ = 1/3 and the consumers are familiar with the distribution, how much is the consumers’ willingness to pay?
(2) In the previous question (1), explain how the used cars are supplied in the market.
(3) To prevent adverse selection, how many good used cars are needed to supply in the market.
(4) Explain ‘adverse selection.’ And also explain from the viewpoints of the consumers’ and retailers’ decisions why we have two cases that adverse selection occurs and not under the identical evaluations of used cars.

下面是答案，楼主满意的话就给币吧。。。。出售的文档是空的。。。


（1）600*1/3+300*2/3＝400
（2）the price that consumes’ willingness to pay is 400, it is lower than the price of good used cars (450), so the retailers do not want to supply the good cars, all the cars sold on the market are bad ones.
(3)600*x+300*(1-x)=450
x=0.5
(4)Adverse selection: it refers to a market process in which "bad" results occur when buyers and sellers have asymmetric information.
Consumers cannot distinguish the quality of any given car, so the price they willing to pay is the average price, which decide the market price of used cars.
Retails can distinguish the quality of cars, if the market price is lower than the true value of cars, they will not want to supply these ones. So the cars on the market will be bad only.
That is the case of adverse selection.

能解释一下为什么吗？？？？？

第一题，应该是600*1/3+300*2/3=400吧

因为消费者不能分辨质量的好坏，因此只愿按照平均价格来付费，据此算出第一问

消费者愿意接受的最高价格为400元，如果超过该价格便没有人愿意买，所以店主不可能将价格定在400元以上。400低于质好的车的价格450，因次店主将不再出售质量好的车，导致市面上出现的车均为劣质的

如果要店主出售质优的车，则消费者愿意接受的价格则必须大于等于450元，据此算出第三问

逆向选择是由信息不对称引起的。举个简单的例子，在金融保险市场上，愿意买保险的人中身体不太好的将占大部分，身体好的只有较小的一部分，因此保险公司获利的空间将缩小，便很有可能提价，而提价将直接挤出那部分身体好的人，因此充斥在保险市场上的将是身体不好的人。这就是逆向选择的作用原理。

只 要 监 狱 不 倒 ， 我 永 远 不 学 好 ！
只 要 论 坛 不 倒 ， 我 永 远 顶 顶 顶 ！