Intermediate Macroeconomic Theory Unit 7 Review: Aggregate Demand & Supply Analysis

Key Concepts

• Aggregate demand (AD) represents the total demand for goods and services in an economy at various price levels
• Aggregate supply (AS) represents the total supply of goods and services in an economy at various price levels
  • Short-run aggregate supply (SRAS) assumes that some input prices are fixed, while others can vary
  • Long-run aggregate supply (LRAS) assumes that all input prices are flexible and the economy operates at full employment
• Equilibrium occurs when AD intersects with AS, determining the economy's price level and real GDP
• Economic fluctuations can be caused by shifts in either the AD or AS curves
• 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 shocks and policies on output and prices
• The model assumes a closed economy, where exports and imports are not considered

Components of Aggregate Demand

• Consumption (C) includes spending by households on goods and services (food, clothing, entertainment)
• Investment (I) consists of spending by businesses on capital goods (machinery, equipment, construction)
  • Residential investment includes the construction of new homes and apartments
  • Non-residential investment includes the purchase of new factories, office buildings, and other structures
• 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
  • Exports are goods and services produced domestically but sold abroad
  • Imports are goods and services produced abroad but purchased domestically
• The AD curve slopes downward due to the wealth effect, interest rate effect, and exchange rate effect

Aggregate Supply: Short-Run vs. Long-Run

• Short-run aggregate supply (SRAS) is upward sloping due to sticky prices and wages
  • Some input prices are fixed in the short run, while others can vary
  • Firms respond to higher prices by increasing output, as they can earn higher profits
• Long-run aggregate supply (LRAS) is vertical at the full-employment level of output
  • All input prices are flexible in the long run, and the economy operates at its potential
  • Changes in the price level do not affect real GDP in the long run
• The SRAS curve shifts due to changes in input prices (wages, raw materials) or productivity
• The LRAS curve shifts due to changes in factors affecting long-run economic growth (technology, labor force, capital stock)

Equilibrium and Economic Fluctuations

• Equilibrium occurs when the quantity of goods and services demanded equals the quantity supplied
  • The intersection of the AD and AS curves determines the equilibrium price level and real GDP
• Short-run equilibrium occurs when the AD curve intersects the SRAS curve
  • This equilibrium may not be at the full-employment level of output
• Long-run equilibrium occurs when the AD curve intersects both the SRAS and LRAS curves
  • This equilibrium is at the full-employment level of output
• Economic fluctuations can be caused by shifts in either the AD or AS curves
  • A shift in the AD curve leads to a movement along the AS curve, affecting both output and prices
  • A shift in the AS curve leads to a movement along the AD curve, affecting both output and prices

Shifts in AD and AS Curves

• The AD curve shifts due to changes in the components of aggregate demand (C, I, G, NX)
  • Factors that can shift AD include changes in consumer confidence, interest rates, government spending, and exchange rates
• The SRAS curve shifts due to changes in input prices or productivity
  • An increase in input prices (oil prices) shifts the SRAS curve to the left, while a decrease shifts it to the right
  • Improvements in productivity shift the SRAS curve to the right, as more output can be produced at each price level
• The LRAS curve shifts due to changes in factors affecting long-run economic growth
  • An increase in the labor force, capital stock, or technological progress shifts the LRAS curve to the right
• Shifts in the AD and AS curves can lead to changes in the equilibrium price level and real GDP

Policy Implications

• Fiscal policy involves changes in government spending and taxation to influence AD
  • Expansionary fiscal policy (increased spending or reduced taxes) shifts the AD curve to the right, increasing output and prices
  • Contractionary fiscal policy (decreased spending or increased taxes) shifts the AD curve to the left, decreasing output and prices
• Monetary policy involves changes in the money supply and interest rates to influence AD
  • Expansionary monetary policy (increased money supply or lower interest rates) shifts the AD curve to the right, increasing output and prices
  • Contractionary monetary policy (decreased money supply or higher interest rates) shifts the AD curve to the left, decreasing output and prices
• Supply-side policies aim to increase LRAS by improving productivity and efficiency
  • Examples include tax reforms, deregulation, and investments in education and infrastructure

Real-World Applications

• The Great Recession (2007-2009) can be analyzed using the AD-AS model
  • The financial crisis led to a decrease in consumption and investment, shifting the AD curve to the left
  • The resulting decrease in output and employment represented a movement along the SRAS curve
• The COVID-19 pandemic (2020) caused both demand and supply shocks
  • Lockdowns and reduced consumer spending shifted the AD curve to the left
  • Supply chain disruptions and business closures shifted the SRAS curve to the left
• The AD-AS model can be used to analyze the effects of oil price shocks
  • An increase in oil prices shifts the SRAS curve to the left, leading to higher prices and lower output
  • The magnitude of the impact depends on the economy's dependence on oil and the response of AD

Common Pitfalls and Misconceptions

• Confusing the short run and long run
  • In the short run, both output and prices can change due to shifts in AD or SRAS
  • In the long run, only the price level changes, while output remains at the full-employment level
• Assuming that the economy always operates at full employment
  • The economy can be in equilibrium at any point along the SRAS curve, not just at the intersection with LRAS
• Ignoring the role of expectations
  • Expectations about future inflation and economic conditions can influence current spending and investment decisions
• Overlooking the importance of supply-side factors
  • While AD is important, long-run economic growth ultimately depends on factors affecting LRAS (productivity, technology, labor force)
• Misinterpreting the shape of the LRAS curve
  • The LRAS curve is vertical, not upward sloping, as changes in the price level do not affect real GDP in the long run