宏观经济学consumption(编辑修改稿)

宏观经济学consumption(编辑修改稿)内容摘要：

’s optimal C1 is less than Y1. C1 C2 Y1 slide 26 CHAPTER 16 Consumption Consumer optimization when the borrowing constraint is binding The optimal choice is at point D. But since the consumer cannot borrow, the best he can do is point E. C1 C2 Y1 D E slide 27 CHAPTER 16 Consumption 在借贷约束下是增加了还是减少了财政政策对总需求的影响。  暂时减税 暂时减税意味着现期的可分配收入增加。 有借贷约束的消费增量等于减税量。 财政政策在有借贷约束时更有力。  宣布未来减税 意味着未来时期的可分配收入增加。 有借贷约束的无法增加现期消费 财政政策在有没有借贷约束时更有力。 slide 28 CHAPTER 16 Consumption The LifeCycle Hypothesis  due to Franco Modigliani (1950s)  Fisher’s model says that consumption depends on lifetime ine, 人们试图获得平稳消费。  The LCH says that ine varies systematically over the phases of the consumer’s “life cycle,” and saving allows the consumer to achieve smooth consumption. slide 29 CHAPTER 16 Consumption The LifeCycle Hypothesis  The basic model: W = initial wealth Y = annual ine until retirement (assumed constant) R = number of years until retirement T = lifetime in years  Assumptions:  zero real interest rate (for simplicity)  consumptionsmoothing is optimal slide 30 CHAPTER 16 Consumption The LifeCycle Hypothesis 一生资源 Lifetime resources = W + RY  To achieve smooth consumption, consumer divides her resources equally over time: C = (W + RY )/T , or C = aW + bY where a = (1/T ) is the marginal propensity to consume out of wealth 财富的边际消费倾向 b = (R/T ) is the marginal propensity to consume out of ine收入的边际消费倾向 slide 31 CHAPTER 16 Consumption Implications of the LifeCycle Hypothesis The LCH can solve the consumption puzzle:  The lifecycle consumption function implies APC = C/Y = a(W/Y ) + b 不同家庭的收入变化比财富变化更频繁，高收入家庭比低收入家庭的 APC更低。 Across households, ine varies more than wealth, so highine households should have a lower APC than lowine households. 在长期里，总财富和收入同时增长， APC稳定。 Over time, aggregate wealth and ine grow together, causing APC to remain stable. slide 32 CHAPTER 16 Consumption Implications of the LifeCycle Hypothesis The LCH implies that saving varies systematically over a person’s lifetime. Saving Dissaving Retirement begins End of life Consumption Ine $ Wealth slide 33 CHAPTER 16 Consumption 老年人的消费和储蓄  生命周期理论表明，老年人应该有负储蓄。 但是实际上，老年的负储蓄并没有达到模型预期的成都 预防性储蓄 ——寿命长，生病的可能性大。 遗产动机  中国人口红利和中国的高储蓄率， 20年以后，中国的储蓄率一定会下降。 slide 34 CHAPTER 16 Consumption The Permanent Ine Hypothesis  due to Milton Friedman (1957)  Y = Y P + Y T where Y = current ine Y P = permanent ine average ine, which people expect to persist into the future Y T = transitory ine temporary deviations from average ine slide 35 CHAPTER 16 Consumption The Permanent Ine Hypo。