宏观经济学第四版课后习题答案

第 2 篇 宏观经济的短期模型........................................................................................................................ 90 第 7 章 总需求与总供给........................................................................................................................ 90 7.1 复习笔记 ................................................................................................................................. 90 7.2 课后习题详解 .......................................................................................................................... 96 7.3 名校考研真题详解 ..................................................................................................................100 第 8 章 总需求理论..............................................................................................................................102 8.1 复习笔记 ................................................................................................................................102 8.2 课后习题详解 ......................................................................................................................... 117 8.3 名校考研真题详解 ..................................................................................................................128 第 9 章 总供给理论..............................................................................................................................132 9.1 复习笔记 ................................................................................................................................132 9.2 课后习题详解 .........................................................................................................................142 9.3 名校考研真题详解 ..................................................................................................................150 第 10 章 开放经济的短期均衡..............................................................................................................153 10.1 复习笔记...............................................................................................................................153 10.2 课后习题详解........................................................................................................................164 10.3 名校考研真题详解.................................................................................................................168 第 11 章 宏观经济政策和理论 ..............................................................................................................174 11.1 复习笔记...............................................................................................................................174 11.2 课后习题详解........................................................................................................................180 11.3 名校考研真题详解.................................................................................................................184

Chapter 9Credit Market Imperfections: Credit Frictions,Financial Crises and Social SecurityTextbook Question SolutionsQuestions for Review1. Borrowers face higher interest rates than lenders.2. The Ricardian equivalence does not hold. Credit constraint household will not save at least part of thetax cut an consume it.3. Yes, there is room for government intervention, in the form of social security or by holding positivepublic debt.4. Asymmetric information and limited commitment.5. The default premium can increase if more consumers are likely to default.6. As consumers face a higher interest rate when borrowing, they borrow less and thus consume lesstoday.7. Such a borrower must reduce the size of her loan, and thus her consumption. She may also want todefault, thereby increasing the default premium and the interest rate of other borrowers, who also reduce their consumption.8. Pay-as-you-go Social Security always improves the welfare of the first generation to receive benefits.Later generations only see a welfare improvement if the population growth rate exceeds the real rate of interest.9. Fully funded Social Security has no effects as long as taxes collected are less than the optimal amountof saving. If taxes and benefits are larger, then individuals consume less when working and more when retired relative to what they would prefer.10. The government cannot commit not to take care of destitute senior citizens. This leads to an incentivenot to save, at least for the poor. With social security, there should be no destitute senior citizens, and the aggregate savings rate is higher as everyone saves optimally for retirement.Problems1. (a) The government intertemporal budget constraint is, assuming both t and t′ are positive:84 Williamson • Macroeconomics, Fourth Edition 1(1)0(1)bt b at r ′+−=+ (b) We are in a situation where asymmetric information becomes important: the government doesnot know who will be able to pay the future taxes. The relevant interest rate is the onecorresponding to the steeper part of the budget constraint, and the new endowment thus movesthe flatter part down. Consumption choices of the first period consumers are thus impactedthrough a negative income shock, as they have to pay more taxes to compensate for more unpaidtaxes in the future.(c) The Ricardian equivalence does not apply as the change in timing of taxes has changed someconsumption patterns. Indeed, households cannot fully adjust their savings, thus any change inperiodic disposable income has an impact at least for some households.2. (a) The government can only tax in the second period as much as it could get from the collateral:t ′ ≤ pH(b) Now that the government has priority on the collateral, the new collateral constraint is:−s (1 + r ) ≤ pH − t ′which implies(1)/(1)y t pH c r t r −+≤′+−+ (c) As we see from the new collateral constraint, Ricardian equivalence holds, as any shifting oftaxes across periods does not affect the constraint. The consumer makes the same consumptionchoice.3. (a) The bank will be lending so that it will be able to get the loan back in expectation. Thus, the newcollateral constraint isChapter 9 Credit Market Imperfections: Credit Frictions, Financial Crises and Social Security 85−s (1 + r ) ≤ a pHwhich leads to .(1)y t a pH c r −+≤+ This is much like Figure 9.5 in the textbook, simply with a lower collateral value.(b) If the collateral is more likely to be of no value, banks will lend less. Thus, some household willnot be able to borrow as much as they could before, leading for them and in aggregate to areduction of current consumption and an increase in future consumption. Thus we have exactlythe same impact as if we had a reduction in p , as in Figure 9.5 of the textbook.4. Social Security.(a) When the program is first instituted, the current old receive b in benefits and pay nothing.The effect on the current old is as in Figure 9.8 in the text. The current young receive b inbenefits when they are old. This effect is also captured by the shift from BA to FD in thetext’s Figure 9.8. The current young also lend bN to the government in period T and receive(1)r bN + in principal and interest when they are old. In per capita terms, these amounts are/(1)/(1)bN n N b n +=+ and (1)/(1)(1)/(1)r bN n N r b n ++=++ respectively. However, thisborrowing and lending are represented in Figure 9.8 as movements along the budget line.Unless there is a change in the real interest rate, there is no additional shift in the budget line.Therefore, both these generations unambiguously benefit from the program.(b) Once the program is running, it is identical to the pay-as-you-go system in the text. This programbenefits a typical cohort as long as n > r , as is depicted in textbook Figure 9.9. A specialcircumstance applies to the cohort born in period T + 1. These individuals each receive a benefit per capita of b /(1 + r ) in present value terms. However, they pay taxes to support two generations’worth of benefits. They pay taxes to retire the principal and interest on debt incurred in period T . The per capita share of principal and interest on their grandparents’ benefits is equal to(1 + r )b /(1 + n )2. The per capita share of their parents’ benefits is equal to b /(1 + n ). This generation can only benefit if:22(1)(1)1(1)(1)r r n n ++>+++ This requirement is obviously more stringent than .n r >5. Under this regime, disposable income for the young is y , but the price of current consumption is(1 + s ). This implies that the intertemporal budget constraint of the household is now(1)(1)(1)(1)s c c y y b r r r ′′+++=++++ In equibrium, it must be that sc (1 + n ) = b . Thus whether there is going to be a positive income effectis going to depend on n is larger than r . But the is also a substitution effect coming from the change in relative price between c and c ′. This substitution effect has no impact on welfare, though.86 Williamson • Macroeconomics, Fourth Edition6. (a) Consumers born in T are the first ones not to get benefits. The government finances the benefitsof the last generation, bN, with bonds D T. Thus each consumer born in T buys D T/N′ bonds, orb/(1 + n) each. In T +1, the government has to reimburse principal and interest, (1 +r)D T, thuseach old consumer at that time obtains (1 +r)b/(1 +n). This means that for the intertemporalbudget constraint in the figure below, the endowment point is shifted b/(1 + n) to the left and(1 +r)b/(1 +I) up. This is on the same budget constraint as before. However, this household isalso losing the old-age benefits it was expecting, thus the new endowment point shifts anadditional b down. However, this generation does not have to pay, when young, for the benefitsof the previous generation, as they are covered by the debt. Thus, the endowment point shiftsb/(1 +n) to the right. As r> n, the new endowment point is now to the right of the old budgetconstraint, see the figure below, and this household is better of. Essentially, it just the opposite of the situation that made it viable to institute a pay-as-you-go system when n > r. The exact samereasoning applies to all future generations.。

高鸿业宏观经济学课后习题答案第五章宏观经济政策实践一、选择题1.政府的财政收入政策通过哪一个因素对国民收入产生影响？A、政府转移支付B、政府购买C、消费支出D、出口2.假定政府没有实行财政政策，国民收入水平的提高可能导致：A、政府支出增加B、政府税收增加C、政府税收减少D、政府财政赤字增加3.扩张性财政政策对经济的影响是:A、缓和了经济萧条但增加了政府债务B、缓和了萧条也减少了政府债务C、加剧了通货膨胀但减轻了政府债务D、缓和了通货膨胀但增加了政府债务4.商业银行之所以有超额储备，是因为：A、吸收的存款太多B、未找到那么多合适的贷款C、向中央银行申请的贴现太多D、以上几种情况都可能5.市场利率提高，银行的准备金会：A、增加B、减少C、不变D、以上几种情况都可能6.中央银行降低再贴现率，会使银行准备金：A、增加B、减少C、不变D、以上几种情况都可能7.中央银行在公开市场卖出政府债券是企图：A、收集一笔资金帮助政府弥补财政赤字B、减少商业银行在中央银行的存款C、减少流通中基础货币以紧缩货币供给D、通过买卖债券获取差价利益二、计算题1、假设一经济有如下关系：C=100+0.8Yd（消费）I=50（投资）g=200（政府支出）Tr=62.5（政府转移支付）t=0.25（边际税率）单位都是10亿美元（1）求均衡收入；（2）求预算盈余BS；（3）若投资增加到I=100时，预算盈余有何变化？为什么会发生这一变化？（4）若充分就业收入y*=1200，当投资分别为50和100时，充分就业预算盈余BS*为多少？（5）若投资I=50，政府购买g=250，而充分就业收入仍为1200，试问充分就业预算盈余为多少？答案：（1）Y=C+I+G=100+0.8Yd+50+200=100+0.8（Y-0.25Y+62.5）+250 解得Y=1000 （2）BS=tY- G- TR=0.25×1000-200-62.5=-12.5（3）Y=C+I+G=100+0.8（Y-0.25Y+62.5）+100+200 解得Y=1125BS=tY- G - TR=0.25×1125-200-62.5=18.75由预算赤字变成了预算盈余，因为投资增加，带动产出增加，在相同的边际税率下税收增加，导致出现盈余。

第二十二章 宏观经济学在目前的争论和共识1、简述货币主义的基本观点和政策主张。

解答：（1）货币主义的基本观点可概括为：第一，货币供给对名义收入变动具有决定性作用；第二，在长期中，货币数量的作用主要在于影响价格以及其他用货币表示的量，而不能影响就业量和实际国民收入；第三，在短期中，货币供给量可以影响实际变量，如就业量和实际国民收入；第四，私人经济具有自身内在的稳定性，国家的经济政策会使它的稳定性遭到破坏。

（2）货币主义的政策主张可概括为如下三点：其一，反对凯恩斯主义的财政政策；其二，反对“斟酌使用”的货币政策；其三，力主“单一政策规则”，即以货币供给量作为货币政策的唯一控制指标，排除利率、信贷流量、准备金等因素。

2、简述新古典宏观经济学的假设条件。

解答：新古典宏观经济学的假设条件主要有个体利益最大化、理性预期、市场出清和自然率假设。

新古典宏观经济学认为，宏观经济现象是个体经济活动的后果。

微观经济学表明，理解个体行为的一个基本出发点就是假设个体追求其最大利益。

所以，要使宏观经济学具有坚实的微观基础，应将个体利益最大化作为基本假设。

所谓理性预期是经济当事人在有效的利用一切信息的前提下，对经济变量作出在长期中平均来说最为准确的，而 又与所使用的经济理论、模型相一致的预期。

用通俗的话说，理性预算假设的意思是，在长期中人们回准确地或趋向于预算到经济变量所应有的数值。

市场出清假设是说，无论劳动市场上的工资还是产品市场上价格都具有充分的灵活性，可以根据供求情况选择迅速进行调整，使相应市场的供给和需求相等或趋向于相等。

自然率假说认为，任何一个社会都存在着一个自然失业率，其大小取决于该社会的技术水平、资源数量和文化传统等，而在长期中，该社会的 总是趋向于自然失业率。

3、推倒卢卡斯总供给曲线。

解答：一个典型企业的供给函数由下式给出：*()i i y h P P y =−+i i 其中y i 为企业的产量，P i 为其产品的价格，P 为价格水平，y*i 为企业的潜在产量，h 表示企业对其产品价格与价格总水平偏离的一种反应，h>0 用Pe 表示企业对价格总水平P 的估计，从而有：*()e i i y h P P y =−+………………………………………………………..(1) 进一步地，企业对价格总水平的估计假定按下式进行： ˆˆ()e i P b P P P =−+…………………………………………………………… (2) 上式表示，企业对价格总水平的估计由两部分组成：一部分是该社会的有关机构预测并公布的价格预测值；另一部分是企业根据其经验对预测值的调整，参数b 为调整系数。