But students of economics will no doubt remember an early encounter with “Giffen goods,” which violate the usual pattern. When tortillas become more expensive, a poor Mexican worker may eat more of them, because she now has to cut back on more expensive food like meat.
部分答案在于经济学是一门不精确的科学，几乎所有经济学家视为理所当然的行为模式都存在例外。比如，经济学家预测商品价格的升高会减少对它的需求。但经济学学生毫无疑问在学习生涯伊始就会遇到“吉芬商品”，这种商品就不符合这一规律。当墨西哥玉米饼变得更贵时，贫穷的墨西哥工人 可能会吃更多的玉米饼，因为他不得不削减更贵的食品（比如肉类）的消费。