曼昆宏观经济学第13章
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related, so the SRAS curve is upward-sloping.
CHAPTER 13
Aggregate Supply
3
The sticky-price model
Reasons for sticky prices: long-term contracts between firms and
2
Introduction
Both models imply:
Y Y (P E P )
agg. output
natural rate of output a positive parameter expected price level
actual price level
Other things equal, Y and P are positively
w h e re s (1 s ) a 0
CHAPTER 13
Aggregate Supply
9
The imperfect-information model
Assumptions: All wages and prices are perfectly flexible, all markets are clear. Each supplier produces one good, consumes many goods. Each supplier knows the nominal price of the good she produces, but does not know the overall price level.
© 2010 Worth Publishers, all rights reserved
SEVENTH EDITION
In this chapter, you will learn:
two models of aggregate supply in which
output depends positively on the price level in the short run
Aggregate Supply
CHAPTER 13
4
The sticky-price model
An individual firm’s desired price is:
p P a (Y Y )
where a > 0. Suppose two types of firms:
• firms with flexible prices, set prices as above • firms with sticky prices, must set their price
MACROECONOMICS
N. Gregory Mankiw
PowerPoint® Slides by Ron Cronovich
CHAPTER
13
Aggregate Supply and the Short-run Tradeoff Between Inflation and Unemployment
so she produces more. With many producers thinking this way, Y will rise whenever P rises above EP.
CHAPTER 13
Aggregate Supply
11
Summary & implications
Phillips curve:
Unemployment is related to unexpected movements in the inflation rate.
CHAPTER 13
SRAS equation: Y Y ( P E P )
P
LRAS
SRAS2 SRAS1
P3 E P3
P2
P1 E P1
AD2 AD1
Y
Y 3 Y1 Y
Y2
13
Aggregate Supply
Inflation, Unemployment, and the Phillips Curve
about the short-run tradeoff between inflation
and unemployment known as the Phillips curve
Introduction
In previous chapters, we assumed the price
level P was “stuck” in the short run. This implies a horizontal SRAS curve.
customers menu costs firms not wishing to annoy customers with frequent price changes
Assumption: Firms set their own prices
(e.g., as in monopolistic competition).
Subtract (1s)P from both sides:
sP s [ E P ] (1 s )[ a (Y Y )]
Divide both sides by s :
P EP
CHAPTER 13
(1 s ) a s
(Y Y )
7
Aggregate Supply
(4 )
( P P 1 ) ( E P P 1 ) ( 1 ) ( Y Y )
(5 )
(6 )
E (1 ) (Y Y )
(1 ) (Y Y ) (u u )
n
(7 )
CHAPTER 13
E (u u )
Supplier does not know price level at the time
she makes her production decision, so uses EP.
Suppose P rises but EP does not. Supplier thinks her relative price has risen,
The Phillips curve states that depends on expected inflation, E. cyclical unemployment: the deviation of the actual rate of unemployment from the natural rate supply shocks, (Greek letter “nu”).
before they know how P and Y will turn out:
p EP a(EY EY )
CHAPTER 13
Aggregate Supply
5
The sticky-price model
p EP a(EY EY )
Assume sticky price firms expect that output will
equal its natural rate. Then,
p EP
To derive the aggregate supply curve,
first find an expression for the overall price level.
s=
fraction of firms with sticky prices. Then, we can write the overall price level as…
The sticky-price model
P EP (1 s ) a s (Y Y )
High EP High P
If firms expect high prices, then firms that must set prices in advance will set them high. Other firms respond by setting high prices.
E (u u )
n
where > 0 is an exogenous constant.
CHAPTER 13
Aggregate Supply
14
Deriving the Phillips Curve from SRAS
(1 ) (2 ) (3 ) Y Y (P E P ) P E P (1 ) (Y Y ) P E P (1 ) (Y Y )
Aggregate Supply
CHAPTER 13
6
Fra Baidu bibliotek
The sticky-price model
P s [ E P ] (1 s )[ P a (Y Y )]
price set by sticky price firms price set by flexible price firms
CHAPTER 13
Aggregate Supply
8
The sticky-price model
P EP (1 s ) a s (Y Y )
Finally, derive AS equation by solving for Y :
Y Y ( P E P ),
High Y High P
When income is high, the demand for goods is high. Firms with flexible prices set high prices. The greater the fraction of flexible price firms, the smaller is s and the bigger is the effect of Y on P.
Now, we consider two prominent models of
aggregate supply in the short run: Sticky-price model Imperfect-information model
CHAPTER 13
Aggregate Supply
P
P EP P EP P EP
LRAS
Y Y (P E P)
SRAS
Y
Y
Both models of agg. supply imply the relationship summarized by the SRAS curve & equation.
12
CHAPTER 13
n
Aggregate Supply
15
Comparing SRAS and the Phillips Curve
SRAS: Y Y (P E P )
P h illip s cu rv e :
E (u u )
n
SRAS curve:
Output is related to unexpected movements in the price level.
CHAPTER 13
Aggregate Supply
10
The imperfect-information model
Supply of each good depends on its relative
price: the nominal price of the good divided by the overall price level.
Aggregate Supply
Summary & implications
Suppose a positive AD shock moves output above its natural rate and P above the level people had expected.
Over time, E P2 EP rises, SRAS shifts up, and output returns to its natural rate.
CHAPTER 13
Aggregate Supply
3
The sticky-price model
Reasons for sticky prices: long-term contracts between firms and
2
Introduction
Both models imply:
Y Y (P E P )
agg. output
natural rate of output a positive parameter expected price level
actual price level
Other things equal, Y and P are positively
w h e re s (1 s ) a 0
CHAPTER 13
Aggregate Supply
9
The imperfect-information model
Assumptions: All wages and prices are perfectly flexible, all markets are clear. Each supplier produces one good, consumes many goods. Each supplier knows the nominal price of the good she produces, but does not know the overall price level.
© 2010 Worth Publishers, all rights reserved
SEVENTH EDITION
In this chapter, you will learn:
two models of aggregate supply in which
output depends positively on the price level in the short run
Aggregate Supply
CHAPTER 13
4
The sticky-price model
An individual firm’s desired price is:
p P a (Y Y )
where a > 0. Suppose two types of firms:
• firms with flexible prices, set prices as above • firms with sticky prices, must set their price
MACROECONOMICS
N. Gregory Mankiw
PowerPoint® Slides by Ron Cronovich
CHAPTER
13
Aggregate Supply and the Short-run Tradeoff Between Inflation and Unemployment
so she produces more. With many producers thinking this way, Y will rise whenever P rises above EP.
CHAPTER 13
Aggregate Supply
11
Summary & implications
Phillips curve:
Unemployment is related to unexpected movements in the inflation rate.
CHAPTER 13
SRAS equation: Y Y ( P E P )
P
LRAS
SRAS2 SRAS1
P3 E P3
P2
P1 E P1
AD2 AD1
Y
Y 3 Y1 Y
Y2
13
Aggregate Supply
Inflation, Unemployment, and the Phillips Curve
about the short-run tradeoff between inflation
and unemployment known as the Phillips curve
Introduction
In previous chapters, we assumed the price
level P was “stuck” in the short run. This implies a horizontal SRAS curve.
customers menu costs firms not wishing to annoy customers with frequent price changes
Assumption: Firms set their own prices
(e.g., as in monopolistic competition).
Subtract (1s)P from both sides:
sP s [ E P ] (1 s )[ a (Y Y )]
Divide both sides by s :
P EP
CHAPTER 13
(1 s ) a s
(Y Y )
7
Aggregate Supply
(4 )
( P P 1 ) ( E P P 1 ) ( 1 ) ( Y Y )
(5 )
(6 )
E (1 ) (Y Y )
(1 ) (Y Y ) (u u )
n
(7 )
CHAPTER 13
E (u u )
Supplier does not know price level at the time
she makes her production decision, so uses EP.
Suppose P rises but EP does not. Supplier thinks her relative price has risen,
The Phillips curve states that depends on expected inflation, E. cyclical unemployment: the deviation of the actual rate of unemployment from the natural rate supply shocks, (Greek letter “nu”).
before they know how P and Y will turn out:
p EP a(EY EY )
CHAPTER 13
Aggregate Supply
5
The sticky-price model
p EP a(EY EY )
Assume sticky price firms expect that output will
equal its natural rate. Then,
p EP
To derive the aggregate supply curve,
first find an expression for the overall price level.
s=
fraction of firms with sticky prices. Then, we can write the overall price level as…
The sticky-price model
P EP (1 s ) a s (Y Y )
High EP High P
If firms expect high prices, then firms that must set prices in advance will set them high. Other firms respond by setting high prices.
E (u u )
n
where > 0 is an exogenous constant.
CHAPTER 13
Aggregate Supply
14
Deriving the Phillips Curve from SRAS
(1 ) (2 ) (3 ) Y Y (P E P ) P E P (1 ) (Y Y ) P E P (1 ) (Y Y )
Aggregate Supply
CHAPTER 13
6
Fra Baidu bibliotek
The sticky-price model
P s [ E P ] (1 s )[ P a (Y Y )]
price set by sticky price firms price set by flexible price firms
CHAPTER 13
Aggregate Supply
8
The sticky-price model
P EP (1 s ) a s (Y Y )
Finally, derive AS equation by solving for Y :
Y Y ( P E P ),
High Y High P
When income is high, the demand for goods is high. Firms with flexible prices set high prices. The greater the fraction of flexible price firms, the smaller is s and the bigger is the effect of Y on P.
Now, we consider two prominent models of
aggregate supply in the short run: Sticky-price model Imperfect-information model
CHAPTER 13
Aggregate Supply
P
P EP P EP P EP
LRAS
Y Y (P E P)
SRAS
Y
Y
Both models of agg. supply imply the relationship summarized by the SRAS curve & equation.
12
CHAPTER 13
n
Aggregate Supply
15
Comparing SRAS and the Phillips Curve
SRAS: Y Y (P E P )
P h illip s cu rv e :
E (u u )
n
SRAS curve:
Output is related to unexpected movements in the price level.
CHAPTER 13
Aggregate Supply
10
The imperfect-information model
Supply of each good depends on its relative
price: the nominal price of the good divided by the overall price level.
Aggregate Supply
Summary & implications
Suppose a positive AD shock moves output above its natural rate and P above the level people had expected.
Over time, E P2 EP rises, SRAS shifts up, and output returns to its natural rate.