乘数模型之乘数计算

19
Total Expenditures


Total spending or “aggregate expenditures” may be represented algebraically by the equation: AE=Consumption+Investment+Government Expenditures+Net Exports The aggregate expenditures curve is simply the vertical summation of these four components.
Chapter 24 The Multiplier Model
Yang Yang International Business School, SYSU
Case 1、美国国防支出

20世纪80年代前期里根执政时，美国国防开 支急剧扩张，国防预算从1979年的2710亿美 元飞速增长到1987年的4090亿美元，相当于 GDP的7.5%。国防建设对经济增长起了很 强的刺激作用，帮助经济走出了1981—1982 年的衰退，并且推动了80年代中期经济景 气的形成。
200
4000
3900 3600
3300
3600 3400
3200
300 200
100
200 200
200
3800 3600
3400
16
A Model With Many Names


Some economists refer to the Keynesian model as the “multiplier model” while other call it the aggregate productionaggregate expenditures model. We will use these names interchangeably as we show you how the development and application of the basic Keynesian model gave birth to fiscal policy.
Q
Consumption
p150
21
Government Expenditures
22
Government Expenditures
Account for almost 20 percent of total aggregate expenditures. As with I, the Keynesian model assumes G to be autonomous so that G simply equals autonomous government expenditures G0. As with the investment function, the government expenditure function can be graphically portrayed as a horizontal line.
+
Saving
Potential Output
S
B
0
GDP
Qp
Real GDP, Output
11
_
The Investment Function
Investment (billions)
16
S
I1(1929)
1
I2(1933)
Income
12
Equilibrium：Saving and Investment
2
Case 2: 克林顿的经济政策

1993年克林顿总统实施160亿美元的政府投 资政策，仅占国内生产总值的0.25％，却 使得国内生产总值增加了320亿美元，失业 率降至6％的水平。
3
The Purpose Of This Lesson



Is to illustrate the basic Keynesian multiplier model-arguably one of the most important models in macroeconomic history. Let us understand the mechanism by which changes in spending get translated into changes in output and employment. Multiplier: changes in government purchases, exports, or other exogenous spending streams will also be amplified into larger output changes. We will also introduce you to one of the most important tools in macroeconomics, that of fiscal policy.
17
The Basic Keynesian Model

Provides a straightforward approach to using fiscal policy to close a recessionary gap. In theory, the model may be used to calculate very precisely how much government spending must be increased, or taxes must be cut, to stimulate an economy back to full employment.
4
Content in Brief
The
basic multiplier model multiplier Fiscal policy in the multiplier model
5
What is the multiplier model



It is a macroeconomic theory used to explain how output is determined in the short run. The model explains how shocks to I, NX, Tax, and G can affect output and employment in and economy. The key assumption underlying the model are that wages and prices are fixed and that there are unemployed resourses, in addition we are suppressing the role of monetary policy and assuming that there are no financial market reaction to changes in the economy. (AS-AD, Keynesian multiplier model)
14
Equilibrium：Consumption and Investment
Aggregate Expenditures
Potential Output
Q
C+I
E
.
E
1
E
I
2
.
C
B
Qp Real GDP, Output
15
计划支出与实际支出的差异 将导致产出数量变动。
M
GDP determination where output equals planned spending
20
Investment
Assumed
to occur independently of the level of income.
Algebraically,
this means I is equal to autonomous investment, Io. Therefore, the investment function may be represented as a horizontal line.
6
Price Level
The Assumption Of Fixed Prices
Keynesian Range Inteຫໍສະໝຸດ Baidumediate Range Classical Range
Potential Output
Aggregate Output
The
most important assumption underlying this model is that prices are fixed. didn’t believe this but did believe that when the economy is in the recessionary range, prices and wages were sufficiently inflexible.
Keynes
7
Basic Multiplier model


Output determination with saving and investment Output determination by total expenditures
8
Equilibrium：Saving and Investment consumptin function
1. Level of 2. Planned 3.Planned 4.Planned GDP and consumption saving investment DI (1)-(2) Total planned consumption and investment （2）+（4）
4200
3800
400

23
Total Spending (billions of dollars)
Equilibrium：C+I+G
E
.
E1
C+I+G
C+I E2
.
C
45o

GDP
3,900 Gross domestic product (billions of dollars)
24
The Consumption Function
$400
C=YD
This function intersects the vertical axis at the level of autonomous consumption Co
Consumption (C)
350 300 250 200
Consumption function (C=$50+0.75YD)
Consumption and Saving
+
E
Potential Output
S
.
E
1
E .
0
2
I
GDP
Qp
B
M
_
Real GDP, Output
13
Planned versus Actual Amounts
The
amount of planned or desired consumption or investment given by the consumption function or by the investment demand schedule. The actual amount of consumption or investment measured after the fact.
18
Total Production
Is
defined as the total amount of goods and services produced in the economy. At any point on the 45° line, total desired expenditure exactly equals the total level of output.
150
100 50 0 50 100 150 200 250 300 350 400 450
Disposable Income (Yd)
The Consumption Function
Potential Output Q
Consumption
B
C
Qp Real GDP, Output
10
The Saving Function