Aggregate Supply

Definition and Properties

Aggregate Supply (AS) describes the relationship between the quantity of real GDP supplied (YAS) and the price level, holding all other influences on production constant. It represents the total amount of final goods and services that firms plan to produce in an economy.

• Upward Sloping AS Curve: When the price level rises and the money wage rate is constant, the real wage rate falls, leading to increased employment and higher real GDP supplied.

• Changes in Aggregate Supply:

  • An increase in firms’ costs (e.g., money wage rate, prices of other resources) decreases aggregate supply (shifts AS left).

  • An increase in potential GDP increases aggregate supply (shifts AS right).

Example: If the money wage rate falls, aggregate supply increases and the AS curve shifts rightward.

Aggregate Demand

Definition and Properties

Aggregate Demand (AD) is the relationship between the quantity of real GDP demanded (YAD) and the price level, holding all other influences on expenditure constant. It is the total amount of final goods and services that people, businesses, governments, and foreigners plan to buy.

• AD Formula: Where: CP: Planned consumption IP: Planned investment GP: Planned government purchases NXP: Net exports (exports minus imports)

• Downward Sloping AD Curve:

  • A rise in the price level lowers the buying power of money, decreasing real GDP demanded.

  • Higher price levels increase demand for money, raise interest rates, and reduce spending.

• Changes in Aggregate Demand:

  • Increased expected future income, inflation, or profit raises AD.

  • Tax cuts (fiscal policy) or lower interest rates (monetary policy) increase AD.

Example: A tax cut increases aggregate demand and shifts the AD curve rightward.

Macroeconomic Equilibrium

Definition and Types

Macroeconomic Equilibrium occurs when the quantity of real GDP demanded equals the quantity of real GDP supplied (). The economy can be at, above, or below full employment.

• Full-Employment Equilibrium: Equilibrium real GDP equals potential GDP ().

• Below Full Employment: Equilibrium real GDP is less than potential GDP (recessionary gap).

• Above Full Employment: Equilibrium real GDP exceeds potential GDP (expansionary or inflationary gap).

• Self-Correction Mechanism: If , firms increase production and prices; if , firms decrease production and prices, moving toward equilibrium.

Example: If equilibrium output is less than potential GDP, the economy is in a recessionary gap.

Aggregate Expenditure Multiplier

Planned Aggregate Expenditure and Multiplier Effect

Aggregate demand is measured by planned aggregate expenditure on goods and services:

• Aggregate Expenditure Formula:

• Planned Consumption (CP): Where: : Autonomous consumption (fixed consumption) : Marginal propensity to consume (MPC) : Disposable income (after-tax income)

• Other Components:

  • Taxes: (often simplified to )

  • Investment: (often )

  • Government: (often )

  • Net Exports: (often )

• Equilibrium Condition:

• Equilibrium Output Formula:

• Multiplier Effect: The aggregate demand multiplier magnifies the impact of changes in autonomous expenditure.

Example: If , , , , , , then:

• Setting gives

Additional info: The multiplier effect means that a change in government spending or taxes leads to a larger change in equilibrium output.

Government Budget & Fiscal Policy

Budget Classifications and Policy Responses

The government budget is defined as the difference between government revenue (mainly taxes) and government expenditure:

• Budget Formula:

• Budget Scenarios:

  • Surplus:

  • Deficit:

  • Balanced:

• Fiscal Policy:

  • Expansionary: Increase government spending () or reduce taxes () to stimulate economic growth, especially during downturns.

  • Contractionary: Decrease government spending () or increase taxes () to cool an overheated economy and control inflation.

• Policy Responses to Output Gaps:

  • Recessionary Gap ():

    • Increase government spending ():

    • Reduce taxes ():

  • Expansionary Gap ():

    • Reduce government spending ():

    • Increase taxes ():

• Multiplier: magnifies the impact of fiscal policy changes.

Example: If , , , , , , and , a decrease in exports by 50 will reduce equilibrium output. The government may respond by increasing or reducing to close the gap.

Review Questions and Applications

Conceptual and Calculation Questions

• Movement vs. Shift: An increase in the price level leads to an upward movement along the AS curve.

• AS Curve Shift: A fall in the money wage rate increases aggregate supply and shifts the AS curve rightward.

• AD Curve Shift: A tax cut increases aggregate demand and shifts the AD curve rightward.

• Consumption and Disposable Income: As disposable income increases, planned consumption increases.

• Marginal Propensity to Consume (MPC): If consumption increases by MPC = 0.9$.

• Multiplier Effect: If investment spending increases by $1 million, the AD curve shifts rightward by more than $1 million due to the multiplier.

• Macroeconomic Equilibrium: If real GDP demanded is less than supplied, the price level falls and firms decrease production.

• Business Cycle Peak: At a peak, equilibrium is greater than potential GDP.

• Fiscal Policy to Close Gaps: To close an expansionary gap, increase taxes or reduce government purchases.

• Output Gap Calculation: If equilibrium output is 20,000 and potential output is 25,000, the economy has a recessionary gap that can be closed by increasing government purchases.

• Tax Adjustment: If short-run equilibrium output is 10,000, , and potential output is 9,000, taxes must be increased by approximately 250 to eliminate the output gap.

Summary Table: Fiscal Policy Effects

Policy Actions and Their Impact on Output

Additional info: The multiplier effect means that fiscal policy changes have amplified impacts on real GDP.