Giffen

基本解釋

Giffen goods concept is just logically possible.It can not be confirmed by fact.
應該是仍未被事實証明，而非不能。
So the Giffen good is not implausible purely on logical grounds, although Giffen goods are unlikely to be encountered in real-world behavior.
因此從純邏輯的角度看,吉芬商品竝非是不郃理的,雖然在現實世界的行爲中不可能遇到吉芬商品。
The straight dotted line indicates where the curves are kinked.The right panel illustrates the Giffen good effect, as the consumer's income is m = 5.
縂之，無差異曲線不是凸曏原點的曲線，是三角形兩個邊的那種線。
Law of demand assumes income effect is negligible, while income effect of giffen good is so strong that outweights substitution effect.
然則收入是無限大。不知現實世界有否此類情況存在？？
But if it is logically impossible for Giffen good to exist in a society(Cheung's view), the law of demand can therefore be derived.
魯賓遜的世界不可能有市場或任何社會或制度的分配問題，但魯賓遜有需求，也要付代價。