中微经济讲义6－多物品的需求关系.pdf

Chapter 6 DEMAND RELATIONSHIPS AMONG GOODS By WALTER NICHOLSON Slides prepared by Linda Ghent (Eastern Illinois University) Modified by Huihua NIE (Renmin Unversity of China) 1 The Two-Good Case • From P -x to P -x x y • Consider two goods case: if Py , what happens to x? • It depends on the relationship. 2 Substitutes and Complements • Two goods are substitutes if one good may replace the other in use – examples: tea coffee, butter margarine • Two goods are complements if they are used together – examples: coffee cream, fish chips Is there any relationships that are both substituting and complementary? 3 Gross Substitutes and Complements • The concepts of gross substitutes and complements include both substitution and income effects – two goods are gross substitutes if x /p 0 i j – two goods are gross complements if x /p 0 i j 4 Gross Substitutes Quantity of y For nearly linear curve, substitution effect is so large but income effect is little, so there is less x and more y y1 In this case, we call x and y gross substitutes y0 U