无差异曲线用排序的方法描述消费者偏好，坐标图用商品价格定位，是一个很完美很简洁的模型。但是，效用函数的值是否有意义呢？基数效用论认为有意义，我们因此估计风险溢价的取值范围；序数效用论认为没有意义，谁能说清楚2.5倍的幸福和3.5倍的幸福之间具体是多大距离。微观经济学第七版第三章有一道习题学生提出了自己的看法，我们这些经济学家习以为常的用来考学生对序数效用论理解和把握程度的一道小题，于是我向我的学生学习，大胆地求教原作者PINDYCK教授，回信的是合作作者RUBINFELD教授。鲁教授也说我们的思考有道理。哈哈，虽然谁都知道准确答案，但是我们的小丫头们居然敢质疑，中国有希望^^ ，但是希望他们考研的时候不会遇到这个题啊。
From: [email protected]
Date: 2012-07-11 12:08:05
To: [email protected]
Cc: [email protected]
Subject: utility
thanks for your note; you are correct; we will have to revise the answer
when we do our next revision or printing. the two individuals clearly
have different cardinal utility functions. ordinal comparisons cannot be
made, but that was not the focus of the question.
From: "WANG Yaling" <[email protected]>
Date: 2012-07-08 09:52:58
To: [email protected]
Subject: puzzle about utility ^^
Dear Professor,
I am teaching Microeconomics(7th edition) at Qingdao University, China. Exercise5 in Chapter3 is puzzling us. Many students, including myself, consider the answer to (c)"Do you think Bridget and Erin have the same preferences?" depends on whether we believe in cardinal utility. Your text book is very popular, while just as popular is a Study Guide book in Chinese by Jin Shencai, which gave an absolute answer saying "yes". Bridget and Erin have the same preferences because they have the same indifference curves. I think it is reasonable to say that both equations can be used to describe the preference relation of one person, while different equations about different persons are not the same. Within ordinal utility theory, they can not be compared directly. Their preferences may be similar, not the same in this case.
Best wishes
----------------
sincerely yours
joni y. l. wang