05elasticity课件.ppt

5 弹性及其运用 Elasticity and Its Applications 谷贱伤农； 为什么在粮食丰收的年份，农民的收入水平却下降了？ 为什么各家电企业却经常打价格战？ 弹性 Elasticity . . . 在上一章，我们分别研究了供给曲线和需求曲线。 In Previous chapter, we studied Demand curve and supply curve, respectively. 每个人都对经济中的变化作出反应。 Everyone responds changes in the economy. 当价格变化，人们会调整其供给和需求。 我们用一个衡量尺寸来描述消费者和生产者如何对市场条件（价格）变化而变化。 When prices change, people will adjust their supply and demand.We need a measure that can describe how much buyers and sellers respond to changes in market conditions (Prices). 这就是弹性! That is Elasticity! 当价格下降When price falls down from P1 to P2 (left panel.) Quantity(数量) demanded increases from Q1 to Q2 (right panel.) Quantity demanded increases from Q’1 to Q’2 两种情况下，商品数量的变化有很大的不同，为什么？However, there is some much difference between these two changes in quantity. Why? THE ELASTICITY OF DEMAND 需求的价格弹性是 商品价格变化引起的该种商品需求数量的变化程度。 Price elasticity of demand is a measure of how much the quantity demanded of a good responds to a change in the price of that good. 需求的价格弹性是价格变化一个百分比引起的需求数量变化的百分比。Price elasticity of demand is the percentage change in quantity demanded given a percent change in the price.  需求的价格弹性及其决定因素。The Price Elasticity of Demand and Its Determinants 相近替代品的可得性。 Availability of Close Substitutes 必需品与奢侈品。 Necessities versus Luxuries 市场的定义。 Definition of the Market 时间长短。 Time Horizon 需求的价格弹性及其决定因素 The Price Elasticity of Demand and Its Determinants 需求弹性越大: Demand tends to be more elastic : 相近替代品越多。the larger the number of close substitutes. 商品是奢侈品。if the good is a luxury. 市场定义范围更窄。 the more narrowly defined the market. 时间越长。the longer the time period. 计算需求的价格弹性 Computing the Price Elasticity of Demand 需求价格弹性是，需求量变化的百分比除以价格变化的百分比。The price elasticity of demand is computed as the percentage change in the quantity demanded divided by the percentage change in price. 需求的价格弹性 Price Elasticity of Demand 假设 Assume 猪肉的价格下跌2% ，需求量增加6% 。The price of pork falls by 2% and the quantity demanded increases by 6% 猪肉的需求价格弹性是 Then the price elasticity of dem