布兰查德：高级宏观经济学ch07

M Y Y , G, T P
( , , )
Macroeconomics, 3/e Olivier Blanchard
© 2003 Prentice Hall Business Publishing
7-3
Equilibrium in the Short Run and in the Medium Run
1. When Y > Yn, P > Pe. 2. When Y < Yn, P < Pe.
3. An increase in Pe shifts the AS curve up, and a decrease in Pe shifts the AS curve down.
© 2003 Prentice Hall Business Publishing Macroeconomics, 3/e Olivier Blanchard
P P (1 ) F (u, z)
e
In words, the price level depends on the expected price level and the unemployment rate. We assume that and z are constant.
© 2003 Prentice Hall Business Publishing
© 2003 Prentice Hall Business Publishing
Macroeconomics, 3/e
Olivier Blanchard
Properties of the AS curve
1. The AS curve is upward sloping. As explained earlier, an increase in output leads to an increase in the price level. 2. The AS curve goes through point A, where Y = Yn and P = Pe. This property has two implications:
IS relation: Y C(Y T ) I (Y , i ) G
M LM relation: YL(i ) P
© 2003 Prentice Hall Business Publishing Macroeconomics, 3/e Olivier Blanchard
Aggregate Demand
© 2003 Prentice Hall Business Publishing Macroeconomics, 3/e Olivier Blanchard
1. An increase in output leads to an increase in the
price level. This is the result of four steps:
1. Y N 2. N u
3. u W
4. W P
© 2003 Prentice Hall Business Publishing
CHAPTER
7
Putting All Markets Together: The AS-AD Model
Prepared by: Fernando Quijano and Yvonn Quijano
© 2003 Prentice Hall Business Publishing
Macroeconomics, 3/e
© 2003 Prentice Hall Business Publishing
Macroeconomics, 3/e
Olivier Blanchard
7-2
Aggregate Demand
The aggregate demand relation captures the effect of the price level on output. It is derived from the equilibrium conditions in the goods and financial markets. Recall the equilibrium conditions for the goods and financial markets described in chapter 5:
M Y Y , G, T P
( , , )
© 2003 Prentice Hall Business Publishing
Macroeconomics, 3/e
Olivier Blanchard
Aggregate Demand
Shifts of the Aggregate Demand Curve An increase in government spending increases output at a given price level, shifting the aggregate demand curve to the right. A decrease in nominal money decreases output at a given price level, shifting the aggregate demand curve to the left.
Macroeconomics, 3/e
Olivier Blanchard
Properties of the AS Relation
Y P P (1 ) F 1 , z L
e
The AS relation has two important properties:
© 2003 Prentice Hall Business Publishing
Macroeconomics, 3/e
Olivier Blanchard
Properties of the AS Relation
Y P P (1 ) F S relation has two important properties:
Y AS Relation P P (1 ) F 1 , z L
e
M AD Relation Y Y , G, T P
Equilibrium (即中期均衡)depends on the value of Pe. The value of Pe determines the position of the aggregate supply curve, and the position of the AS curve affects the equilibrium.
2. An increase in the expected price level leads, one
for one, to an increase in the actual price level. This effect works through wages:
1. P e W 2. W P
© 2003 Prentice Hall Business Publishing
Macroeconomics, 3/e
Olivier Blanchard
Aggregate Supply
The Aggregate Supply Curve Given the expected price level, an increase in output leads to an increase in the price level. If output is equal to the natural level of output, the price level is equal to the expected price level.
Therefore, for a given labor force, the higher is output, the lower is the unemployment rate.
© 2003 Prentice Hall Business Publishing
Macroeconomics, 3/e
Aggregate Supply
The Effect of an Increase in the Expected Price Level on the Aggregate Supply Curve An increase in the expected price level shifts the aggregate supply curve up.
W P e F (u, z)
P (1 )W
© 2003 Prentice Hall Business Publishing
Macroeconomics, 3/e
Olivier Blanchard
Deriving the Aggregate Supply Relation
Step 1: Eliminate the nominal wage from: W P e F (u, z) and P (1 )W, then:
The Derivation of the Aggregate Demand Curve An increase in the price level leads to a decrease in output.
M P i demand Y P
© 2003 Prentice Hall Business Publishing
Macroeconomics, 3/e
Olivier Blanchard
Deriving the Aggregate Supply Relation
Step 2: Express the unemployment rate in terms of output:
U L N N Y u 1 1 L L L L
Macroeconomics, 3/e
Olivier Blanchard
Aggregate Demand
Changes in monetary or fiscal policy—or more generally in any variable, other than the price level, that shift the IS or the LM curves—shift the aggregate demand curve, or function.
Olivier Blanchard
Deriving the Aggregate Supply Relation
Step 3: Replace the unemployment rate in the equation obtained in step one:
Y P P (1 ) F 1 , z L
Olivier Blanchard
7-1
Aggregate Supply
The aggregate supply relation captures the effects of output on the price level. It is derived from the behavior of wages and prices. Recall the equations for wage and price determination from chapter 6:
e
In words, the price level depends on the expected price level, Pe, and the level of output, Y (and also , z, and L, but we take those as constant here).