Chapter Fifteen Market Demand 市场需求
Chapter Fifteen Market Demand 市场需求
Structure From Individual to Market Demand Functions ◆Elasticities Revenue and own-price elasticity of demand Marginal revenue and price elasticity
Structure ◆From Individual to Market Demand Functions ◆Elasticities ◆Revenue and own-price elasticity of demand ◆Marginal revenue and price elasticity
From Individual to Market Demand Functions +Think of an economy containing n consumers,denoted by i 1,..,n. Consumer i's ordinary demand function for commodity j is x(p1,P2,m)
From Individual to Market Demand Functions ◆Think of an economy containing n consumers, denoted by i = 1, … ,n. ◆Consumer i’s ordinary demand function for commodity j is xj p p m *i i ( , , ) 1 2
From Individual to Market Demand Functions When all consumers are price-takers, the market demand function for commodity j is n *i X1p1P2,m,,m)=x(P1,P2,m) i=1 If all consumers are identical then Xi(p1,P2,M)=nx xj(P1,P2,m) where M nm
From Individual to Market Demand Functions ◆When all consumers are price-takers, the market demand function for commodity j is ◆If all consumers are identical then where M = nm. Xj p p m m n xj i p p m i i n ( , , , , ) ( , , ). * 1 2 1 1 2 1 = = Xj (p ,p ,M) n xj (p ,p ,m) * 1 2 = 1 2
From Individual to Market Demand Functions +The market demand curve is the “horizontal sum”of the individual consumers'demand curves. E.g.suppose there are only two consumers;i A,B
From Individual to Market Demand Functions ◆The market demand curve is the “horizontal sum” of the individual consumers’ demand curves. ◆E.g. suppose there are only two consumers; i = A,B
From Individual to Market Demand Functions P1 p 20 5 B
From Individual to Market Demand Functions p1 p1 x A 1 * x B 1 20 15 * p1 ’ p1 ” p1 ’ p1
From Individual to Market Demand Functions P1 P1 p4 20 *B p
From Individual to Market Demand Functions p1 p1 x A 1 * x B 1 * x x A B 1 1 * + p1 20 15 p1 ’ p1 ” p1 ’ p1 ” p1 ’
From Individual to Market Demand Functions p1 P1 p 7 p 0
From Individual to Market Demand Functions p1 p1 x A 1 * x B 1 * x x A B 1 1 * + p1 20 15 p1 ’ p1 ” p1 ’ p1 ” p1 ’ p1
From Individual to Market Demand Functions p 20 15 *B X P1 The“horizontal sum” of the demand curves of individuals A and B. 35
From Individual to Market Demand Functions p1 p1 x A 1 * x B 1 * x x A B 1 1 * + p1 20 15 35 p1 ’ p1 ” p1 ’ p1 ” p1 ’ p1 ” The “horizontal sum” of the demand curves of individuals A and B
Elasticities(弹性) ◆Elasticity measures the“sensitivity” of one variable with respect to another. The elasticity of variable X with respect to variable Y is %△x Ex,y %△y
Elasticities （弹性） ◆Elasticity measures the “sensitivity” of one variable with respect to another. ◆The elasticity of variable X with respect to variable Y is x y x y , % % = .