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Introduction to Economic Introduction to Economic FluctuationsFluctuations

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In this chapter, you will learn:In this chapter, you will learn:

facts about the business cycle

how the short run differs from the long run

an introduction to aggregate demand

an introduction to aggregate supply in the short run and long run

how the model of aggregate demand and aggregate supply can be used to analyze the short-run and long-run effects of “shocks.”

3CHAPTER 9 Introduction to Economic Fluctuations

Facts about the business cycle What exactly do we mean by “business cycles:? Business cycles are economy wide fluctuations

in total national output, income, and employment, usually lasting for a period of 2 to 10 years, marked by widespread expansion or contraction in most sectors of the economy.

Economists typically divide business cycles into two main phases: recession and expansion. Peaks and troughs mark the turning points of the cycle. The downturn of a business cycle is called a recession. A recession is a recurring period of decline in total output, income, and employment, usually lasting from 6-12 months and marked by contractions in many sectors of the economy. A recession that is large in both in scale and duration is called a depression.

GDP growth averages 3–3.5 percent per year over the long run with large fluctuations in the short run.

Consumption and investment fluctuate with GDP, but consumption tends to be less volatile and investment more volatile than GDP.

Unemployment rises during recessions and falls during expansions.

Okun’s Law: the negative relationship between GDP and unemployment.


Time horizons in macroeconomics

Long run Prices are flexible, respond to changes in supply or demand.

Short runMany prices are “sticky” at a predetermined level.

The economy behaves much differently when prices are sticky.


Recap of classical macro theory (Chaps. 3-8)

Output is determined by the supply side: supplies of capital, labor technology

Changes in demand for goods & services (C, I, G ) only affect prices, not quantities.

Assumes complete price flexibility.

Applies to the long run.


When prices are sticky…

…output and employment also depend on demand, which is affected by:

fiscal policy (G and T )

monetary policy (M )

other factors, like exogenous changes in C or I


The model of aggregate demand and supply

The paradigm most mainstream economists and policymakers use to think about economic fluctuations and policies to stabilize the economy

Shows how the price level and aggregate output are determined

Shows how the economy’s behavior is different in the short run and long run


Aggregate demand (AD) The aggregate demand curve shows the relationship between the price level and the

quantity of output demanded. AD is the total or aggregate quantity of output that is willingly bought at a given price, other things held constant. AD is the desired spending in all product sectors: Consumption, private domestic investment, government purchases of goods and services, and net exports.

AD consists of four components- consumption (C), domestic private investment (I), government spending on goods and services (G), and net exports (NX).

Aggregate demand shifts when there are changes in macroeconomic policies (such as monetary-policy changes or changes in government expenditures or tax rates) or exogenous events change spending ( as would be the case with changes in output, affecting NX, or in business confidence, affecting I).


Aggregate demand (AD)Impact on AD

Variables:

Monetary policy: Monetary expansion may lower inter interest rates and loosen credit conditions, inducing higher levels of investment and consumption of durable goods. In an open economy, monetary policy also affects the exchange rates and net exports (NX).

Fiscal Policy: Increases in government purchases of goods and services directly increase spending, tax reductions or increases in transfers raise disposable income and induce higher consumption. Tax incentives like investment tax credit can induce higher spending in a particular sector.


The Quantity Equation as Aggregate Demand

From Chapter 4, recall the quantity equation

M V = P Y

For given values of M and V, this equation implies an inverse relationship between P and Y …


The downward-sloping AD curve

An increase in the price level causes a fall in real money balances (M/P ),

causing a decrease in the demand for goods & services.

An increase in the price level causes a fall in real money balances (M/P ),

causing a decrease in the demand for goods & services. Y

P

AD


Shifting the AD curve

An increase in the money supply shifts the AD curve to the right.

An increase in the money supply shifts the AD curve to the right.

Y

P

AD1

AD2


Aggregate supply in the long run

Recall from Chapter 3: In the long run, output is determined by factor supplies and technology

is the full-employment or natural level of output, at which the economy’s resources are fully employed.

“Full employment” means that unemployment equals its natural rate (not zero).


The long-run aggregate supply curve

Y

P LRAS

does not depend on P,

so LRAS is vertical.

does not depend on P,

so LRAS is vertical.


Long-run effects of an increase in M

Y

P

AD1

LRASAn increase in M shifts AD to the right.

P1

P2In the long run, this raises the price level…

…but leaves output the same.

AD2


Aggregate supply in the short run

Many prices are sticky in the short run.

We assume all prices are stuck at a predetermined level in

the short run. firms are willing to sell as much at that price

level as their customers are willing to buy.

Therefore, the short-run aggregate supply (SRAS) curve is horizontal:


The short-run aggregate supply curve

Y

P

SRAS

The SRAS curve is horizontal:

The price level is fixed at a predetermined level, and firms sell as much as buyers demand.

The SRAS curve is horizontal:

The price level is fixed at a predetermined level, and firms sell as much as buyers demand.


Short-run effects of an increase in M

Y

P

AD1

In the short run when prices are sticky,…

…causes output to rise.

SRAS

Y2Y1

AD2

…an increase in aggregate demand…


From the short run to the long run

Over time, prices gradually become “unstuck.” When they do, will they rise or fall?

rise

fall

remain constant

In the short-run equilibrium, if

then over time, P will…

The adjustment of prices is what moves the economy to its long-run equilibrium.

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An increase in aggregate demand: The economy begins in long-run equilibrium at point A. An increase in aggregate demand, perhaps due to an increase in the velocity of money, moves the economy from point A to point B, where output is above its natural level. As prices rise, output gradually returns to its natural level, and the economy moves from point B to point C.

The SR & LR effects of ΔM > 0

Y

P

AD1

LRAS

SRAS

P2

Y2

A = initial equilibrium

AB

CB = new short-run

eq’m after central bank increases M

C = long-run equilibrium

AD2


How shocking!!!

shocks: exogenous changes in agg. supply or demand

Shocks temporarily push the economy away from full employment.

Example: exogenous decrease in velocity

If the money supply is held constant, a decrease in V means people will be using their money in fewer transactions, causing a decrease in demand for goods and services.


SRAS

LRAS

AD2

The effects of a negative demand shock

Y

P

AD1P2

Y2

AD shifts left, depressing output and employment in the short run.

AD shifts left, depressing output and employment in the short run. AB

C

Over time, prices fall and the economy moves down its demand curve toward full-employment.


Supply shocks

A supply shock alters production costs, affects the prices that firms charge. (also called price shocks)

Examples of adverse supply shocks: Bad weather reduces crop yields, pushing up

food prices. Workers unionize, negotiate wage increases. New environmental regulations require firms to

reduce emissions. Firms charge higher prices to help cover the costs of compliance.

Favorable supply shocks lower costs and prices.


Stabilization policy

def: policy actions aimed at reducing the severity of short-run economic fluctuations. Because output and employment fluctuate around their long-run natural levels, stabilization policy dampens the business cycle by keeping output and employment as close to their natural levels as possible.

Example: Using monetary policy to combat the effects of adverse supply shocks…


Stabilizing output with monetary policy

SRAS1

Y

P

AD1

B

A

Y2

LRAS

The adverse supply shock moves the economy to point B.

SRAS2


Stabilizing output with monetary policy

Y

P

AD1

B

A

C

Y2

LRASBut the central bank accommodates the shock by raising agg. demand.

results: P is permanently higher, but Y remains at its full-employment level.

SRAS2

AD2