08金融 梁剑雄
Tel：15013229729
QQ：424143870
E-mail： 424143870@qq.com
Outline
 Macroeconomic Policy
 Controversies Over Macroeconomic Policy
 Some Reviews on Quizzes
The AS-AD Model
P
AS
AD
Y*
Y
Outline
 Macroeconomic Policy
 Controversies Over Macroeconomic Policy
 Some Reviews on Quizzes
The Great Depression
Explanation of Great Depression
 John Keynes’ explanation
 Milton Friedman’s explanation
Some Concepts
 Inflation
 The Sacrifice Ratio
 Unemployment
Objectives of Macroeconomic
Policy
 Economic growth
 Full employment
 A stable general price level
 External Balance
Demand Management Policy
 Stabilization policy, or demand management policy, is
designed to control aggregate demand so as to achieve
the objectives discussed above.
 Fiscal policy, varying government expenditure and/or
taxes;
 Monetary policy, changing the interest rate, or ,the
supply of money
Analytical Framework
 IS-LM Model
i
IS
LM
IS-LM model can help us
analyze the effects of
policies in the short-run.
i*
 AS-AD Model
Y*
Y
P
If the price level can
adjust, our analysis
should be proceeded
under AS-AD
framework.
ＡD
Y*
Y
Review: Instruments of Monetary
Policy
 Open market operations
 The discount rate
 The required-reserve ratio
Intermediate Target
 Money supply
 Interest
 Credit
 etc
How can the government achieve
their goals?
Change in an
Instrument
e.g. open
market
operation
Change in an
Intermediate
Target
Change in
an Ultimate
Target
e.g. Money
Supply
e.g. level of
employment
Monetary Policy Under IS-LM
Model
 A monetary expansion.
LM1
i
i
L
IS
i*
i*
**
i**
i
M1s
P
M 2s
P
M
P
LM2
Y*
Y **
Y
Summary: Mechanism of Monetary
Policy
Ms ↗
Second Step
(M)s /P↗
i↘
(M)d /P
First Step
Investment↗
output ↗
Two Special Cases: Liquidity Trap
i
LM Curve
Y
Liquidity Trap: Monetary Policy
i
IS
LM
i*
Y*
Y
Two Special Cases: Classical
Quantity Theory
i
LM Curve
 M  D
   kY , (h  0)
 P 

S
M
M 

  

P
 P

M
Y 
kP
Y
( MV  PY )
Classical Quantity Theory: Monetary
Policy
i
LM
LM
Y*
Y **
IS
i*
i**
Y
Monetary Policy: A Numerical Example
 Consider the following model of the economy:
C  200  0.75(Y  T )
I  200  25i
G  100
T  100
Md
 Y  100i
P
P2
M s  1000
 What is the equilibrium level of income Y and interest
rate i? Suppose that government purchases are raised
from 100 to 150, how much does output increase by ?
What about consumption? And private saving?
i
Key
 代数据入 Y  C  I  G
得
 IS曲线： Y  1700  100i
 代数据入 M S / P  Y  100i 得
Y
i

5

 LM曲线：
 均衡
100
Y *  1100, i*  6
Key
 新的IS曲线（IS2，前一条称IS1） Y
 与原LM曲线联立，解得新的均衡
Y **  1200, i**  7
i
 1900  100i
Key
*
*
C

200

0.75(
Y
 T )  950
 两次均衡的消费
C**  200  0.75(Y **  T )  1025
 消费增加了
C*  C**  C*  75
 两次均衡的储蓄 S *  Y *  T  C *  50
 储蓄增加了
S **  Y **  T  C **  75
S *  S **  S *  25
Instrument of Fiscal Policy
 Government purchases
 Investment subsidy (sometimes investment tax credit)
 Transfer payments
 Tax reduction
Fiscal Policy Under IS-LM Model
IS’
i
LM
IS
i**
i
*
Y
*
Y **
Crowding out
Y
Fiscal Policy: The Mechanism
G   Y   i   Crowding Out
Crowding Out Effect: Different Levels
i
IS1’
IS2’
LM
IS1
Y*
Y ** Y ***
Y
IS2
Crowding Out Effect (continued)
i
LM’
LM
IS2
IS1
Y * Y ***Y **
Y
Two Special Cases: Liquidity Trap
i
IS
IS
No crowding out effect!!
i*
LM
Y
*
Y
**
Y
Two Special Cases: Classical
Quantity Theory
i
i
IS
LM
**
i
IS
Only raise interest rate!!
*
Y*
Y
Fiscal Policy: A Numerical Example
 Consider the following model of the economy:
C  200  0.75(Y  T )
I  200  25i
G  100
T  100
Md
 Y  100i
P
P2
M s  1000
 What is the equilibrium level of income Y and interest rate i?
Suppose that government purchases are raised from 100 to
150, h0w large is the crowding out? How much does output
increase by? How about consumption and private saving?
Key
i
Key
 IS1 Y  1700  100i
 IS2
 LM
Y  1900  100i
i  5
Y
100
新均衡 Y **  1200, i**  7
 比较两条方程从IS1到IS2，IS曲线移动了200
 均衡产出增加了100
 因此挤出了100的产出
 消费增加（见前文）75
 私人储蓄增加（见前文）25
 原均衡为 Y *  1100, i*  6
Summary
Type
Equilibrium Y
Expansive
↑
monetary policy
Contractionary
↓
monetary policy
Expansive fiscal
↑
policy
Contractionary
↓
fiscal policy
Equilibrium i
↓
↑
↑
↓
The Policy Mix (1)
IS’
i
LM
IS
LM’
*
1
i
No crowding out
i*
Monetary accommodation
Y
*
Y1* Y **
Y
The Policy Mix (2)
i
Suppose the
government decides to
decrease government i *
spending to reduce
i**
budget deficit….
LM
A recession occurs.
IS2
Y ** Y *
IS1
Y
The Policy Mix (2) (continued)
i
If the central bank
wants to fix the
interest rate…
LM
LM
i*
It deepens the
recession by
keeping the
interest high.
i**
IS1
IS2
Y **
Y*
Y
The Policy Mix (2) (continued)
If the central bank wants to
prevent lower income…
i
LM1
i*
LM2
i* *
IS1
IS2
Y*
Y
Our Old Problem
C  200  0.75(Y  T )
I  200  25i
G  100
T  100
Md
 Y  100i
P
P2
M s  1000
 G becomes 150 after an expansive fiscal policy. In order
to eliminate the crowding out effect entirely, how
much should the money supply be?
Key
i
LM1 LM2
Key
*
i
6
 原均衡利率为
Y1  1300
 代入IS2得
 假定货币供给变为 M 1
M1 / 2  Y 100i
 LM2
 代入
i i* , Y  Y1
 解得
M1  1400
 即要求央行增加货币供给量
M  400
Investment Subsidy
I'
i
i
IS’
i
I
LM
IS
**
i
i*
**
i*
G I
I
O
I0
I0 '
I
Y
*
Y
**
Y
About Intermediate Objective of
Monetary Policy
 The central bank could not control money supply and
interest rate simultaneity.
i
L
i*
M0 P
M P
Deriving LM Curve
i
i
LM
i
LM
*
i*
Y
Intermediate objective : money supply
Y
Intermediate objective : interest rate
Shock in IS Curve
i
i
IS1
LM
IS2
IS1
IS2
LM(i)
i*
i*
Y*
Intermediate objective : money supply
Y
Y*
Y
Intermediate objective : interest rate
Shock in LM Curve
i
IS
LM2
i
LM1
i*
IS
LM(i)
i*
Y*
Y
Intermediate objective : money supply
Y*
Y
Intermediate objective : interest rate
Monetary Policy Under AS-AD
Framework
P
AS
P2
P1
AD1
Y*
Y1
AD2
Y
The Neutrality of Money
 In the long run, the increase in money is reflected
entirely in a proportional increase in the price level.
 The increase in nominal money has no effect on
output.
How Can You Explain This Graph?
Quantity Theory of Money
MV  PY
   g P  g M  gV  gY
Fiscal Policy Under AS-AD
Framework: Example
P
AD1
AS
AD
Y*
A demand shock……
Y
Fiscal Policy Under AS-AD
Framework: Example
P
AD1
AS
AD2
Y*
Fiscal policy is implemented
Y
Recardian Equivalence
 Consumers are forward-looking.
 The forward-looking consumer understands that
government borrowing today means higher taxes in
the future.
 Financing the government by debt is equivalent to
financing it by taxes.
More Examples: Demand Shock
(No Stabilization Policy)
P
AD1
AS
AD
AS1
Y*
Y
Favorable Demand Shock (No
Stabilization Policy)
AS1
P
AS
AD
AD1
Y*
Y
Demand Shock: Stabilization Policy
P
P
AS
AD2
AD1
AD2
AS
AD1
Y*
Y
Y*
Y
Unfavorable Supply Shock
AS1
P
AD
AS
Y*
Y
Unfavorable Supply Shock:
Stabilization Policy
P
AS1
AD1
AD
AS
Y*
Y
Favorable Supply Shock
P
AS
AD
AS1
Y*
Y
Favorable Supply Shock
P
AS
AD
AD1
AS1
Y*
Y
Favorable Supply Shock:
Technological Progress
P
AD
AS
AS2
AS1
Y*
Y**
Y
Technological Progress: Policy
AD1
P
AS
AD
AS2
AS1
Y*
Y**
Y
Favorable Supply Shock:
Technological Progress (2)
P
AS
AD
AS1
AS2
Y*
Y**
Y
Technological Progress (2) : Policy
P
AD
AS
AS1
AD1
Y*
Y**
Y
Outline
 Macroeconomic Policy
 Controversies Over Macroeconomic Policy
 Some Reviews on Quizzes
Lags
Recognition lag
Inside lag
Decision lag
Action lag
Lags
Outside lag
Lags (continued)
Fiscal Policy
Monetary Policy
Inside lag
Long
Short
Outside lag
Short
Long
If the Disturbance is Transitory …
Y
Y*
t0
t1
time
If the Disturbance is Permanent …
Uncertainty: Could We Predict the
Great Depression?
Lucas Critique
 Lucas critique: The argument that traditional policy
analysis does not adequately take into account the
impact of policy changes on people’s expectations.
 Adaptive expectations: An approach that assumes that
people form their expectation of a variable based on
recently observed values of the variable.
 Rational expectations: An approach that assumes that
people optimally use all available information —
including information about current and prospective
policies — to forecast the future.
Dynamic Inconsistency (Time
Inconsistency): A Model
Suppose the policymaker
controls money growth…
Inflation
rate
At first, the policymaker announces a
zero inflation rate due to its optimality
to the society;
Private agents expect the inflation rate
to be zero; the economy reaches point
A;
P1
The policymaker has the incentive to
move from A to B.
B
A
Natural rate, u*
Therefore, time inconsistency occurs.
Unemployment
rate
Dynamic Inconsistency (continued)
Inflation
rate
However, once the deviation of the
announced policy is observed by
private agents, they would expect a
higher inflation.
P1
B
A
Natural rate, u*
The eventual income is a higher
inflation without reduction in
unemployment rate.
Unemployment
rate
Dynamic Inconsistency: More
Examples
 To encourage investment, the government announces
that it will not tax income from capital. But after
factories have been built, the government is tempted
to renege on its promise to raise more tax revenue from
them.
 To encourage research, the government announces
that it will give a temporary monopoly to companies
that discover new drugs. But after a drug has been
discovered, the government is tempted to revoke the
patent or to regulate the price to make the drug more
affordable.
Dynamic Inconsistency: More
Examples (continued)
 To encourage good behavior, a parent announces that
he or she will punish a child whenever the child breaks
a rule. But after the child has misbehaved, the parent is
tempted to forgive the transgression, because
punishment is unpleasant for the parent as well as for
the child.
 To encourage you to work hard, your professor
announces that this course will end with an exam. But
after you have studied and learned all the material, the
professor is tempted to cancel the exam so that he or
she won’t have to grade it.
Dynamic Inconsistency: A
Numerical Example


1.
2.
What would happen if private agents have rational expectation?
Consider the following game:
Private agents form their expectation of inflation,
The policymaker chooses the actual level of inflation rate;
Suppose the loss function for the policymaker is
L  a(u  u* )   2
 The parameter a reflects the relative importance of
unemployment and inflation in social welfare;
 The quadratic form of inflation rate denotes that the marginal
cost of inflation increases as inflation rises.
Dynamic Inconsistency: A Numerical Example
 How to solve the outcome of this game?
Backward Induction
e
*





(
u
 u)
The short-run Phillips curve:
 At Stage 2,given the expected inflation rate of individuals, the
goal of the policymaker is
1
min L( )  a[ (   e )]   2



The optimal policy is
a
 
2
*
*
u
u*
Dynamic Inconsistency: A
Numerical Example
 At Stage1, individuals understand the objective of the
policymaker and the constraint the Phillips curve imposes;
 Therefore, they could expect the policymaker would choose
this level of inflation,
e * 
a
2
 Consequently, the outcome under discretion is that the
economy suffers a higher inflation rate without any reduction
in unemployment.
Rules versus Discretion
 Consider a policy under a fixed rule.
 Obviously, the optimal rule is to produce zero inflation.
 In both cases, unemployment rate is at its natural rate.
However, discretionary policy produces more inflation.
Therefore, in this model, discretion is worse than the rule.
Rules versus Discretion
 How to avoid, or at least mitigate the consequence of dynamic
inconsistency?
 Determining the monetary policy by rules rather than discretion.
However, rules can’t account for completely unexpected
circumstances.
An Example of Rule
 Money Growth = 3% + (Unemployment Rate - 6%)
 More examples: See Rudiger Dornbusch, P187 –
Taylor’s Rule
Rules versus Discretion:
Further Discussions
 Independence of central bank
 Political Business Cycle: The fluctuations in output and
employment resulting from the manipulation of the economy
for electoral gain.
Outline
 Macroeconomic Policy
 Controversies Over Macroeconomic Policy
 Some Reviews on Quizzes
Quiz A
 什么是总需求曲线？画图说明总需求曲线向右下方倾
斜的机制。中国举办奥运会，将会对中国总需求曲线
带来什么影响？
 给定（不同的）价格水平，产品市场、货币市场同时
均衡的产出。图略（P下降，真实货币供给增加，LM右
移，均衡产出增加）。向外（右）平移（私人投资，
政府购买等等）。
Quiz A
 目前中国消费占GDP的比重大致是多少？请简要阐述
消费理论的发展历程，并结合这些理论分析中国消费
所占比重下降的原因。
 近四成（37%-38%）。凯恩斯的消费理论，莫迪利亚尼
的LC和弗里德曼的PIH，随机游走，等等。要求答出：
1）收入下降；2）收入用于消费的比重下降。具体分
析只要答出以上两点都给分。
Quiz A
Quiz A
注：本题（以及Quiz B的第三题）都没有具体给出价格水平
P等于多少，计算时要保留字母。这是个概念性问题——货
币需求L指的是真实货币需求（demand for real balances）！
Quiz A
 假定一个经济体处于均衡或稳态位置，现在储蓄率一
次性上升，比如从0.4上升到0.5。回答下面问题
 1)如果采用IS－LM模型分析，储蓄率的变化将会对经
济体带来什么影响？
 2)如果采用Solow模型分析，储蓄率的变化将会对经济
体带来什么影响？
 3)采用不同的模型是否得到相同结论？为什么？
Quiz A
 1）IS内旋，产出和利率下降.(作图分析.)
 2）储蓄线上移，稳态水平值提高（不管是人均产出还是有
效人均产出）
 3）不同。IS-LM模型是短期模型，前提是经济体生产过剩需
求不足，储蓄率的一次性增加（通过减少自有消费或减少边
际消费倾向）将减少消费支出（消费需求），进而减少均衡
产出。Solow模型是建立在经济体各要素始终处于充分就业
状态的假设之上，是长期模型。储蓄率增加可以提高资本积
累程度，提高经济长期稳态产出。答案要点：一、前者是短
期模型，后者是长期模型；二、前者讨论的是需求方，后者
模型讨论的是供给方。
注：希望大家能够正确地和准确地做出前两问，首先坐标轴要画对，IS-LM模型横轴
是总产出Y，纵轴是i；Solow 模型纵轴是劳均产出（或有效劳均产出），横轴是劳均
资本存量或有效劳均资本存量。其次，Solow模型各线的大小关系凹凸性以及表达式
要写准确。IS曲线并不是简单平移，当边际消费倾向变化以后IS是进行带有旋转的移
动（请参照我的第三次PPT）。Solow 模型要找对均衡的劳均产出，而不是均衡的劳
均投资！最后，Solow模型的sy 移动不要移错了。
Quiz B
 什么是乘数？在举办亚运会前夕，广州政府回馈市
民，先是免费乘坐公交和地铁，后是给居民补贴。这
两种做法对广东省总需求曲线带来的影响是否相同？
为什么？
 增加一单位某部门的支出引起的（均衡）产出的增加
量。（保持其他条件不变，外生变量对均衡的变化对
均衡的Y的影响。）假定政府的支出都是一样的，只是
前者是属于政府购买(G)，给公交和地铁企业，后者是
以转移支付(TR)的形式给居民，这样二者都会是总需
求曲线右移，前者带来的总需求右移的幅度会更大。
Quiz B
 什么是李嘉图等价？2008年，中国政府发行国债，为
4万亿刺激计划融资。当李嘉图等价成立时，4万亿刺
激计划对中国经济的拉动作用将会如何变化？当中国
大量从欧盟、美国净进口时，4万亿刺激计划对中国经
济的拉动作用将会如何变化？
 现时的国债与未来的税收（负担）是等价的。（发国
债与征税是等价的。）当李嘉图等价成立的时候，相
当于平衡预算时候的政府支出（只考虑商品市场均衡
时财政支出乘数为1）。当出现大量净进口时，拉动作
用减弱。（乘数作用下降。）
Quiz B
Quiz B
注：本题（以及Quiz A的第三题）都没有具体给出价格水平
P等于多少，计算时要保留字母。这是个概念性问题——货
币需求L指的是真实货币需求（demand for real balances）！
Quiz B
 假定一个经济体处于均衡或稳态位置，现在储蓄率一
次性下降，比如从0.4下降到0.3。回答下面问题
 1)如果采用IS－LM模型分析，储蓄率的变化将会对经
济体带来什么影响？
 2)如果采用Solow模型分析，储蓄率的变化将会对经济
体带来什么影响？
 3)采用不同的模型是否得到相同结论？为什么？
Quiz B
 1）IS曲线外旋，产出和利率上升。（作图分析）
 2）储蓄线下移，稳态水平值降低（不管是人均产出还是有效人
均产出）
 3）结论不同。详解：IS-LM模型是短期模型，前提是经济体生
产过剩需求不足，储蓄率的一次性降低（通过增加自有消费或
增加边际消费倾向）将增加消费支出（消费需求），进而减少
均衡产出。Solow模型是建立在经济体各要素始终处于充分就业
状态的假设之上，是长期模型。储蓄率下降会降低资本积累程
度，从而使经济长期稳态产出下降。答案要点：一、前者是短
期模型，后者是长期模型；二、前者讨论的是需求方，后者模
型讨论的是供给方。
注：希望大家能够正确地和准确地做出前两问，首先坐标轴要画对，IS-LM模型横轴
是总产出Y，纵轴是i；Solow 模型纵轴是劳均产出（或有效劳均产出），横轴是劳均
资本存量或有效劳均资本存量。其次，Solow模型各线的大小关系凹凸性以及表达式
要写准确。IS曲线并不是简单平移，当边际消费倾向变化以后IS是进行带有旋转的移
动（请参照我的第三次PPT）。Solow 模型要找对均衡的劳均产出，而不是均衡的劳
均投资！最后，Solow模型的sy 移动不要移错了。
Review
Measurement of output
Three approaches to account GDP
Measurement of price level
Long run: Growth Theory
AS Curve
Short run: Phillips Curve
AD Curve
IS-LM Model
Reference
 王志伟译著，Rudiger Dornbusch, Stanley Fischer
and Richard Startz, Macroeconomics , Tenth
Edition (东北财经大学出版社,2008)
 N. Gregory Mankiw, Macroeconomics, Fifth
Edition (Worth Publishers,2003)
 徐现祥编著，图解宏观经济学，第一版（中国人民大
学出版社，2008）