Aggregate Supply and Aggregate Demand: Macroeconomic Equilibrium, Growth, and Fluctuations

Unit 2: Aggregate Supply and Aggregate Demand

Introduction

This unit explores the fundamental concepts of aggregate supply (AS) and aggregate demand (AD) in macroeconomics. Students will learn how real GDP and the price level are determined, what causes economic growth, inflation, and business cycles, and the main schools of thought in macroeconomic theory.

Aggregate Supply

Definition and Key Concepts

• Aggregate Supply (AS): The relationship between the quantity of real GDP supplied and the price level in an economy.

• Quantity Supplied: The total quantity of goods and services that firms plan to produce during a given period.

• Two time frames are distinguished:

  • Long-run aggregate supply (LRAS): The relationship when real GDP equals potential GDP; independent of the price level.

  • Short-run aggregate supply (SRAS): The relationship when the money wage rate and other resource prices are fixed.

Long-Run Aggregate Supply (LRAS)

• In the long run, the quantity of real GDP supplied equals potential GDP.

• The LRAS curve is vertical at potential GDP, indicating that potential GDP does not depend on the price level.

• Potential GDP: The maximum sustainable output of an economy, determined by resources and technology.

Short-Run Aggregate Supply (SRAS)

• In the short run, the quantity of real GDP supplied increases as the price level rises, assuming constant money wage rate and resource prices.

• The SRAS curve is upward sloping.

• If the price level rises without a change in wages, firms are incentivized to increase production.

Changes in Aggregate Supply

• Aggregate supply shifts when influences on production (other than price level) change.

• Main influences:

  • Changes in potential GDP: Caused by increases in labor, capital, or technological advances. Both LRAS and SRAS shift rightward.

  • Changes in money wage rate (and other factor prices): Higher wages shift SRAS leftward; LRAS remains unchanged.

Aggregate Demand

Definition and Components

• Aggregate Demand (AD): The relationship between the quantity of real GDP demanded and the price level.

• Quantity of real GDP demanded (Y): The total spending on final goods and services by households, businesses, government, and foreigners.

• Components:

  • Consumption (C)

  • Investment (I)

  • Government expenditure (G)

  • Net exports (X - M)

• Aggregate demand equation:

$Y = C + I + G + (X - M)$

Aggregate Demand Curve

• The AD curve plots real GDP demanded against the price level.

• The AD curve is downward sloping due to:

  • Wealth effect: Higher price level reduces real wealth, decreasing consumption.

  • Substitution effects:

    • Intertemporal substitution: Higher price level raises interest rates, reducing current spending.

    • International substitution: Higher price level makes domestic goods less competitive, reducing exports and increasing imports.

Changes in Aggregate Demand

• AD shifts when influences on buying plans (other than price level) change.

• Main influences:

  • Expectations: Higher expected future income, inflation, or profits increase AD.

  • Fiscal policy: Government changes in taxes, transfer payments, and spending affect AD.

  • Monetary policy: Central bank changes in interest rates and money supply affect AD.

  • World economy: Changes in exchange rates and foreign income affect exports and imports.

Macroeconomic Equilibrium

Short-Run Equilibrium

• Occurs where the AD and SRAS curves intersect.

• Real GDP can be above, below, or equal to potential GDP.

• If real GDP is below equilibrium, firms increase production and prices; if above, they decrease production and prices.

Long-Run Equilibrium

• Occurs where AD, SRAS, and LRAS curves intersect at potential GDP.

• Adjustments in the money wage rate move the economy toward long-run equilibrium.

Explaining Macroeconomic Trends and Fluctuations

Economic Growth

• Growth occurs when potential GDP increases due to more labor, capital, or technological progress.

• LRAS shifts rightward, indicating higher sustainable output.

Inflation

• Inflation arises when aggregate demand increases faster than aggregate supply.

• AD curve shifts rightward more rapidly than LRAS, raising the price level.

Business Cycle

• Business cycles are fluctuations in real GDP, employment, and inflation.

• Types of equilibrium:

  • Above full-employment equilibrium: Real GDP exceeds potential GDP (inflationary gap).

  • Full-employment equilibrium: Real GDP equals potential GDP.

  • Below full-employment equilibrium: Real GDP is less than potential GDP (recessionary gap).

Table: Types of Macroeconomic Equilibrium

Type of Equilibrium	Real GDP vs. Potential GDP	Gap
Above Full-Employment	Real GDP > Potential GDP	Inflationary Gap
Full-Employment	Real GDP = Potential GDP	No Gap
Below Full-Employment	Real GDP < Potential GDP	Recessionary Gap

Macroeconomic Schools of Thought

Classical School

• Believes the economy is self-regulating and always at full employment.

• Business cycles are efficient responses to shocks, such as technological change.

• Associated with economists like Adam Smith, David Ricardo, and John Stuart Mill.

Keynesian School

• Argues that the economy rarely operates at full employment without government intervention.

• Active fiscal and monetary policy are needed to achieve and maintain full employment.

• Prices and wages are sticky, preventing quick adjustment.

• Named after John Maynard Keynes.

Monetarist School

• Believes the economy is self-regulating and will operate at full employment if monetary policy is stable.

• Erratic monetary policy can cause instability.

• Associated with economists like Karl Brunner and Milton Friedman.

Key Terms and Examples

• Inflation: A sustained increase in the general price level. Example: Zimbabwe's hyperinflation in the late 2000s.

• Stagflation: A situation with slow economic growth and high inflation. Example: The U.S. economy in the 1970s.

• Hyperinflation: Extremely rapid or out of control inflation. Example: Germany in the 1920s.

Additional info: The notes have been expanded to include definitions, examples, and a summary table for equilibrium types, as well as context for the main schools of macroeconomic thought.