Part 2 需求曲线与供给曲线3——ch06_弹性：对需求与供给的反应.ppt

主动学习 1 计算弹性 主动学习 1 计算弹性 主动学习 2 弹性与支出/收益 A. 药店将胰岛素的价格提高10%，对胰岛素的总支出会增加还是减少？ B. 作为价格战的结果，游轮价格下降了20%。游轮制造公司的收益会增加还是下降？ 主动学习 2 参考答案 主动学习 2 参考答案 主动学习 3 弹性与均衡的改变 主动学习 3 参考答案 主动学习 3 参考答案 习题 如果需求富有弹性，价格上升会如何改变总收益？解释原因 价格变动引起一种物品的需求量减少了30%，而这种商品的总收益增加了15%。这种商品的需求曲线是富有还是缺乏弹性？ 你有以下关于X物品与Y物品的信息 X的需求收入弹性为-3 X与Y的需求交叉价格弹性为2. 收入增加和Y物品的价格下降会对X的需求产生什么变化？ Maria总是把她收入的1/3用于买衣服 1、她对衣服的需求收入弹性是多少 2、她对衣服的需求价格弹性是多少 3、如果她的偏好改变，决定将收入的1/4用于购买衣服，她的需求曲线怎么变？需求收入和需求价格弹性呢？ Tom和jierry分别开车到加油站。在看到价格之前，tom说：我想加10加仑的油。Jerry说：我想加10美元的油。两个司机的需求价格弹性为多少。 * Economists classify demand curves according to their elasticity. The next 5 slides present the five different classifications, from least to most elastic. * If Q doesn’t change, then the percentage change in Q equals zero, and thus elasticity equals zero. It is hard to think of a good for which the price elasticity of demand is literally zero. Take insulin, for example. A sufficiently large price increase would probably reduce demand for insulin a little, particularly among people with very low incomes and no health insurance. However, if elasticity is very close to zero, then the demand curve is almost vertical. In such cases, the convenience of modeling demand as perfectly inelastic probably outweighs the cost of being slightly inaccurate. * An example: Student demand for textbooks that their professors have required for their courses. Here, it’s a little more clear that elasticity would be small, but not zero. At a high enough price, some students will not buy their books, but instead will share with a friend, or try to find them in the library, or just take copious notes in class. Another example: Gasoline in the short run. * This is the intermediate case: the demand curve is neither relatively steep nor relatively flat. Buyers are neither relatively price-sensitive nor relatively insensitive to price. (This is also the case where price changes have no effect on revenue.) * A good ex