💸Principles of Economics Unit 24 – Aggregate Demand & 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 that all input prices are flexible
• Equilibrium occurs when AD intersects with AS, determining the economy's price level and real GDP
• Shifts in AD or AS cause changes in the equilibrium price level and real GDP
• Fiscal policy involves government spending and taxation to influence AD
• Monetary policy involves central bank actions to control the money supply and interest rates, affecting AD

Components of Aggregate Demand

• Consumption (C) includes spending by households on goods and services (food, clothing, entertainment)
  • Disposable income, consumer confidence, and wealth affect consumption
• Investment (I) includes spending by businesses on capital goods (machinery, equipment, buildings)
  • Interest rates, expectations of future profitability, and technology influence investment decisions
• Government spending (G) includes expenditures by federal, state, and local governments (infrastructure, defense, education)
• Net exports (NX) represent the difference between exports and imports
  • Exchange rates, foreign income levels, and trade policies impact net exports

Components of Aggregate Supply

• SRAS is upward sloping due to sticky prices and wages in the short run
  • Sticky prices and wages prevent some input costs from adjusting quickly to changes in the price level
• LRAS is vertical because, in the long run, input prices fully adjust to changes in the price level
• Shifts in SRAS can be caused by changes in input prices (oil prices), productivity, or government regulations
• Shifts in LRAS are driven by factors that affect the economy's potential output, such as changes in the quantity and quality of labor, capital, or technology

Equilibrium and Shifts

• Changes in any component of AD (C, I, G, or 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 input prices, productivity, or government regulations can shift the SRAS curve
  • An increase in SRAS shifts the curve to the right, while a decrease shifts it to the left
• Shifts in LRAS are caused by changes in factors affecting potential output (labor, capital, technology)
  • An increase in LRAS shifts the curve to the right, while a decrease shifts it to the left
• Shifts in AD or AS lead to new equilibrium points, affecting the price level and real GDP

Macroeconomic Policies

• Expansionary fiscal policy aims to increase AD through increased government spending or reduced taxes
  • This policy can help stimulate the economy during a recession but may lead to budget deficits
• Contractionary fiscal policy aims to decrease AD through reduced government spending or increased taxes
  • This policy can help control inflation but may slow economic growth
• Expansionary monetary policy involves increasing the money supply or lowering interest rates to stimulate AD
  • Lower interest rates encourage borrowing and spending, but excessive expansion may lead to inflation
• Contractionary monetary policy involves decreasing the money supply or raising interest rates to control AD
  • Higher interest rates discourage borrowing and spending, helping to control inflation but potentially slowing growth

Real-World Applications

• The Great Recession (2007-2009) was characterized by a significant decline in AD, leading to falling prices and high unemployment
  • Governments and central banks implemented expansionary fiscal and monetary policies to stimulate the economy
• The COVID-19 pandemic (2020) caused a sharp decline in AD due to lockdowns and reduced consumer spending
  • Governments provided fiscal support (stimulus checks, unemployment benefits) to help stabilize the economy
• Supply shocks, such as oil price spikes (1970s) or natural disasters, can shift the SRAS curve, leading to stagflation (high inflation and low growth)
• Long-term economic growth is driven by factors that shift LRAS, such as investments in education, research and development, and infrastructure

Common Misconceptions

• Confusing AD with quantity demanded or AS with quantity supplied
  • AD and AS refer to the entire relationship between price level and output, not a specific quantity
• Believing that the economy always operates at full employment
  • Shifts in AD or AS can cause the economy to deviate from full employment, resulting in unemployment or inflationary gaps
• Thinking that fiscal and monetary policies have immediate and predictable effects
  • Policy actions often involve lags and can have unintended consequences or be offset by other factors
• Assuming that economic models perfectly reflect reality
  • Models are simplified representations of complex economic relationships and may not capture all relevant factors

Study Tips and Exam Prep

• Create a glossary of key terms and concepts (AD, AS, SRAS, LRAS, equilibrium, fiscal policy, monetary policy)
• Practice drawing and interpreting AD-AS diagrams, focusing on the effects of shifts in AD and AS
• Analyze real-world examples to understand how the AD-AS model applies to current events and policy decisions
• Discuss concepts with classmates or form study groups to reinforce understanding and identify areas for improvement
• Review past exam questions and practice applying the AD-AS model to solve problems
• Summarize the main points of each topic in your own words to ensure comprehension
• Use mnemonic devices or create visual aids to help remember key relationships and effects of policy actions