💵Principles of Macroeconomics Unit 11 – Aggregate Demand and Supply Model

Key Concepts

• Aggregate demand (AD) represents the total demand for goods and services in an economy at a given price level
• Aggregate supply (AS) represents the total supply of goods and services in an economy at a given price level
• Short-run aggregate supply (SRAS) assumes that some input prices are fixed, while long-run aggregate supply (LRAS) assumes all input prices are flexible
• Equilibrium occurs when AD intersects with AS, determining the equilibrium price level and real GDP
• Economic shocks can shift the AD or AS curves, leading to changes in the equilibrium price level and real GDP
• Fiscal and monetary policies can be used to influence AD and stabilize the economy
• The AD-AS model helps analyze the effects of various economic events and policies on price levels, output, and employment

Components of Aggregate Demand

• Consumption (C) includes spending by households on goods and services (food, clothing, entertainment)
  • Depends on factors such as disposable income, wealth, and consumer confidence
• Investment (I) consists of spending by businesses on capital goods (machinery, equipment, buildings)
  • Influenced by interest rates, expectations of future profitability, and technological advancements
• Government spending (G) encompasses expenditures by federal, state, and local governments on goods and services (infrastructure, defense, education)
• Net exports (NX) represent the difference between exports and imports
  • Affected by exchange rates, foreign income levels, and trade policies
• The AD curve slopes downward, indicating that as the price level decreases, the quantity of goods and services demanded increases

Components of Aggregate Supply

• SRAS is upward sloping, reflecting the positive relationship between the price level and the quantity of goods and services supplied in the short run
  • In the short run, some input prices (wages) are fixed, allowing for increased output as prices rise
• LRAS is vertical, indicating that the economy's potential output is independent of the price level in the long run
  • In the long run, all input prices are flexible, and the economy operates at its full potential
• Factors affecting AS include changes in input prices (wages, raw materials), productivity, technology, and government regulations
• Positive supply shocks (technological advancements) shift the AS curve to the right, while negative supply shocks (natural disasters) shift it to the left

Equilibrium and Shifts

• Equilibrium occurs at the intersection of the AD and AS curves, determining the equilibrium price level and real GDP
• Changes in any of the components of AD (C, I, G, NX) can shift the AD curve
  • An increase in AD shifts the curve to the right, while a decrease shifts it to the left
• Changes in factors affecting AS (input prices, productivity, technology, regulations) can shift the AS curve
  • An increase in AS shifts the curve to the right, while a decrease shifts it to the left
• Shifts in AD or AS lead to a new equilibrium price level and real GDP
  • The extent of the change depends on the magnitude of the shift and the slopes of the curves

Economic Shocks and Their Effects

• Demand shocks are unexpected events that affect the components of AD (changes in consumer confidence, investment, or government spending)
  • Positive demand shocks shift AD to the right, increasing both the price level and real GDP
  • Negative demand shocks shift AD to the left, decreasing both the price level and real GDP
• Supply shocks are unexpected events that affect the components of AS (changes in input prices, natural disasters, or technological breakthroughs)
  • Positive supply shocks shift AS to the right, decreasing the price level and increasing real GDP
  • Negative supply shocks shift AS to the left, increasing the price level and decreasing real GDP
• Stagflation occurs when an economy experiences both high inflation and high unemployment, often caused by a negative supply shock

Policy Implications

• Fiscal policy involves changes in government spending and taxation to influence AD
  • Expansionary fiscal policy (increased spending or reduced taxes) shifts AD to the right, aiming to stimulate economic growth
  • Contractionary fiscal policy (decreased spending or increased taxes) shifts AD to the left, aiming to control inflation
• Monetary policy involves changes in the money supply and interest rates by the central bank to influence AD
  • Expansionary monetary policy (lower interest rates or increased money supply) shifts AD to the right, aiming to stimulate economic growth
  • Contractionary monetary policy (higher interest rates or decreased money supply) shifts AD to the left, aiming to control inflation
• Policymakers must consider the trade-off between inflation and unemployment when implementing fiscal and monetary policies

Real-World Applications

• The Great Recession (2007-2009) was characterized by a significant leftward shift in AD due to a housing market crash and financial crisis
  • Governments and central banks implemented expansionary fiscal and monetary policies to stimulate economic recovery
• The COVID-19 pandemic (2020) caused both demand and supply shocks, leading to a simultaneous leftward shift in AD and AS
  • Governments provided fiscal support (stimulus checks, unemployment benefits) to mitigate the economic impact
• Oil price shocks (1973, 1979) are examples of negative supply shocks that led to stagflation
  • Central banks faced the challenge of balancing inflation control with economic growth

Common Misconceptions

• The AD-AS model is a simplified representation of the economy and may not capture all real-world complexities
• The model assumes a closed economy, which may not always be the case in an increasingly globalized world
• The distinction between the short run and long run is not always clear-cut and can vary depending on the context
• The model does not explicitly account for the role of expectations, which can influence economic behavior
• Policymakers may face challenges in accurately assessing the state of the economy and implementing timely and effective policies
• The effectiveness of fiscal and monetary policies can be limited by factors such as the liquidity trap, crowding out, and policy lags