Which of the following is least likely to be a characteristic of a Giffen good?Its:
A.demand curve slopes upward.
B.substitution effect is negative.
C.income effect is negative.
Answer:B
A Giffen good is an inferior good.All inferior goods have a negative income effect(less is purchased as income rises).Although the substitution effect is always positive for all goods,for a Giffen good,the income effect is so strong and so negative that it overpowers the substitution effect.The result is that as its price declines,less of it is purchased;this relationship results in a positively sloped individual demand curve.Therefore,it is least likely that the substitution effect is negative.
解析：
这题考的是吉芬商品。
首先，明确，吉芬商品和韦伯伦商品不同，它是在需求理论下受替代效应和收入效应影响的。
然后，吉芬商品属于劣质品，所以收入效应为负。
同时，吉芬商品，因为替代效应永远为正，所以替代效应为正。
关键在于，吉芬商品和普通劣质品不同的是，它的收入负效应大于替代正效应。
最后，吉芬商品需求曲线的斜率为正，图像为向右上方倾斜。
我们来看这道题目，A选项需求曲线斜率为正，是对的；B选项，替代效应为负，是错的；C选项，收入效应为负，是对的。这题问哪个错，所以选B。
