Household Saving and Investment Decisions.ppt

1、Chapter 5: Household Saving and Investment Decisions,2,Chapter 5 Contents,5.1 A Life-Cycle Model of Savings 5.2 Taking Account of Social Security 5.3 Deferring Taxes through Voluntary Retirement Plans 5.4 Should you Invest in a Professional Degree? 5.5 Should you Buy or Rent?,Copyright Prentice Hall

2、 Inc. 2000. Author: Nick Bagley, bdellaSoft, Inc.,E.g： How much to save for retirement Whether to get a professional degree Whether to buy or rent an apartment,4,5.1 A Life-Cycle Model of Saving,Assume that you are currently 35 years old, expect to retire in 30 years at 65, and then live for 15 more

3、 years until 80 Your real labor income is $30,000/year until age 65 Interest rates exceed inflation by 3%/ year,How Much Should I Save and Consume? Consider two approaches: Target replacement rate of pre-retirement income Maintain the same level of consumption spending,为退休的储:1： 例：王二今年30岁，计划在65岁退休，预计

4、自己能活到80岁。他的实际薪水为每年10万元。不考虑税收、不存在实际劳动收入增长的前提下，如果实际利率为3%，王二的目标替代率是退休前收入的75%，他必须每年为自己的养老储蓄多少？ 用年金现值方法得到养老金的现值，也即在65时必须存够的财富： 每年必须储蓄的年金为：,PV=PMT*(1-(1+i)n)/i=PV(3%,15,75000,0)=895345,PMT=FV*i/(1+i)n-1=PMT(3%,35,0,895345)=14808,两个概念,Human Capital 人力资本 即未来劳动收入的现值（截止退休） Permanent income 永久性收入 即现值等于人力资本的不变收

5、入或消费水平（直到去世）,Fig. 5.1 Salary, Consumption, and Saving over the Life Cycle,Fig.5.2 Human Capital, Retirement Assets, and Total Wealth over the Life Cycle,为退休的储蓄2： 例：王二今年30岁，计划在65岁退休，预计自己能活到80岁。他的实际薪水为每年不变的10万元，而且打算在接下来的50年里保持实际消费支出水平不变。如果实际利率为3%，请问王二的人力资本价值为多少？永久性收入呢？ 先按照年金现值计算方法得到人力资本为： 永久性收入为：,=PV(

6、3%,35,100000,0)=2,148,722,=PMT(3%,50,2148722,0)=83,511,为退休的储蓄,接上例 薪水的终值是多少？ 退休时的财富呢？ 每年储蓄100000-83511=16489元，相当于投资于一项年金，退休时的财富即为该年金的终值：,=FV(3%,35,16489,0)=996,959,Intertemporal budget constraint跨期预算约束,C=年消费金额 i = 利率 R = 距离退休年数 T = 余生年数 Y =薪水收入 W0= 继承的财富；初始财富 B t= 遗产 P155. Quick Check 5-4,Is there on

7、ly one solution of consumption spending plan or many? Feasible plan Choose the one that gives you the biggest satisfaction or utility Optimization model,Fig. 5.3 Omars Life-Cycle Savings Plan,如果王二还面临强制性的社保缴纳，比如每年交5000，假设社保投资按同样的实际利率获得收益，那么他个人的储蓄和退休时每期的收入是多少？ Whats the benefits? The longer you live,

8、the more you get 退休金体系与人口压力 现收现付制（pay-as-you-go）与累积制 高福利下的欧洲与做实个人账户的我国,5.2 Taking Account of Social Security,Invest in human capital Explicit costs and implicit costs Investment is worthwhile if: The PV of the expected incremental benefits exceeds the PV of the expected incremental costs,5.4 Should

9、You Invest a Degree,买房还是租房? 租房每个月2500元 买房总价100万元 假定你的目标是以最低的成本现值给自己提供住房，假定扣除通货膨胀后的每年实际折现率为3%（房租和房价的真实增长率）。假设剩余寿命50年。 Q：买还是租？,5.5 Should You Buy or Rent?,买房和租房的现值成本,买房的现值成本即为100万 租房的现值成本为：=PV(0.25%,600,2500,0)，其中实际利率为3%，月0.25%。求得租房的现值成本为78万左右 买房后每个月节约下来的租金可以视为收入 租售比（月租金/房价）可以用来衡量泡沫。通常认为正常的租售比在1:2001:300之间,为什么大家还是买房？,买房的其他成本：维护；房