Aggregate Demand, Aggregate Supply, and Macroeconomic Fluctuations: Core Concepts in Macroeconomics

Recent Economic Activity and Labor Market Trends

Employment and Labor Force Dynamics

Recent data show fluctuations in employment and labor force participation, which are key indicators of macroeconomic health. The unemployment rate is calculated as the percentage of people in the labor force who are actively seeking work but are not employed. Changes in the labor force can affect the unemployment rate even if employment itself does not change significantly.

• Unemployment Rate: Calculated as $\text{Unemployment Rate} = \frac{\text{Number of Unemployed}}{\text{Labor Force}}$

• Labor Force: Includes both employed and unemployed individuals actively seeking work.

• Discouraged Workers: Individuals not actively seeking work due to belief that no jobs are available for them are not counted in the labor force.

Aggregate Demand and Aggregate Supply (AD-AS) Model

Aggregate Demand (AD)

The aggregate demand curve shows the relationship between the overall price level and the quantity of real GDP demanded by households, firms, and the government. It is downward sloping due to three main effects:

• Wealth Effect: Higher prices reduce the real value of money, decreasing consumer spending.

• Interest-Rate Effect: Higher prices lead to higher interest rates, reducing investment and consumption.

• International Trade Effect: Higher domestic prices make exports less competitive, reducing net exports.

Shifts in the AD curve can be caused by changes in monetary and fiscal policy, expectations, and foreign variables.

Aggregate Supply (AS)

Aggregate supply describes the total output firms are willing to produce at various price levels. There are two key curves:

• Long-Run Aggregate Supply (LRAS): Vertical at the level of potential (full-employment) GDP, determined by the number of workers, capital stock, and technology. Not affected by the price level.

• Short-Run Aggregate Supply (SRAS): Upward sloping because input prices (like wages) adjust more slowly than output prices, increasing profitability as prices rise.

Shifts in SRAS can result from changes in the labor force, capital stock, technology, expected future prices, and supply shocks (e.g., oil price spikes, natural disasters).

Macroeconomic Equilibrium

Long-run equilibrium occurs where AD, SRAS, and LRAS intersect—at full employment and stable prices. Short-run equilibrium can deviate due to shocks or policy changes.

Supply Shocks and Stagflation

Supply shocks, such as sudden increases in oil prices, shift the SRAS curve leftward, causing stagflation—a combination of rising unemployment and inflation.

Case Study: The COVID-19 Recession

The 2020 recession was unique in that both aggregate demand and aggregate supply declined. The pandemic caused business closures, reduced consumption and investment, and disrupted global supply chains, shifting both AD and SRAS leftward.

Measuring Economic Activity: GDP and Its Components

Gross Domestic Product (GDP)

GDP measures the market value of all final goods and services produced within a country in a given period. It can be measured by total production or total income, as every dollar spent is income for someone else.

• Expenditure Approach: $\text{GDP} = C + I + G + NX$ where C = Consumption, I = Investment, G = Government Spending, NX = Net Exports

• Final Goods: Only final goods are counted to avoid double counting; intermediate goods are excluded.

Real vs. Nominal GDP

Real GDP adjusts for changes in the price level, using base-year prices, while nominal GDP uses current prices. The GDP deflator measures the overall price level:

• $\text{Real GDP} = \frac{\text{Nominal GDP}}{\text{Price Index}}$

• $\text{GDP Deflator} = 100 \times \frac{\text{Nominal GDP}}{\text{Real GDP}}$

Limitations of GDP

• Does not include the underground economy or non-market activities.

• Does not account for environmental harm or the value of leisure.

Disposable Personal Income

Disposable personal income is personal income minus personal tax payments—income available for spending or saving.

Unemployment and Inflation

Types of Unemployment

• Frictional: Short-term, due to job search and matching.

• Structural: Due to mismatches between skills and job requirements.

• Cyclical: Due to economic downturns.

Measuring Inflation

The Consumer Price Index (CPI) is the most common measure of inflation, calculated as the percentage change in the cost of a fixed basket of goods and services.

• Inflation affects purchasing power and can have uneven effects across the population.

• Unanticipated inflation can hurt lenders and those on fixed incomes.

Long-Term Economic Growth

Real GDP per Capita

Real GDP per capita is the best measure of living standards over time and across countries, as it adjusts for population size.

Determinants of Economic Growth

• Physical capital accumulation (factories, equipment)

• Human capital (education, skills, health)

• Technological progress

The Market for Loanable Funds

Interest Rates and Loanable Funds

The market for loanable funds determines the real interest rate through the interaction of borrowers (demand) and lenders (supply). The equilibrium interest rate balances the quantity of funds supplied and demanded.

Shifts in Loanable Funds Market

Factors that shift the supply or demand for loanable funds include government deficits, household saving preferences, tax incentives, expected profitability, and corporate taxes.

An increase in ...	Will shift the ...	Causing ...
Government's budget deficit	Supply curve left	Higher real interest rate, lower investment
Household desire to consume today	Supply curve left	Higher real interest rate, lower investment
Tax benefits for saving	Supply curve right	Lower real interest rate, higher investment
Expected future profits	Demand curve right	Higher real interest rate, higher investment
Corporate taxes	Demand curve left	Lower real interest rate, lower investment

Business Cycles and Macroeconomic Fluctuations

The Business Cycle

The business cycle consists of alternating periods of economic expansion and recession. Peaks mark the transition from expansion to recession, while troughs mark the transition from recession to expansion.

Aggregate Expenditure and Output in the Short Run

Aggregate expenditures (AE) represent total planned spending in the economy. If AE equals GDP, the economy is in equilibrium. If AE is less than GDP, inventories rise and firms cut production; if AE exceeds GDP, inventories fall and firms increase production.

If ...	Then ...	And ...
Aggregate expenditure equals GDP	Inventories unchanged	Macroeconomic equilibrium
Aggregate expenditure less than GDP	Inventories rise	GDP and employment decrease
Aggregate expenditure greater than GDP	Inventories fall	GDP and employment increase

The Multiplier Effect

The multiplier quantifies how an initial change in autonomous expenditure leads to a larger change in equilibrium GDP. It is calculated as:

• $\text{Multiplier} = \frac{1}{1 - \text{MPC}}$

• Where MPC is the marginal propensity to consume.

• Example: If MPC = 0.75, Multiplier = 4. A $200 billion increase in investment leads to an $800 billion increase in GDP.

Determinants of Key Macroeconomic Variables

Consumer Spending

• Disposable income (after taxes)

• Household wealth

• Expected future income

• Price level

• Interest rates

Planned Investment

• Expectations of future profitability

• Interest rates

• Taxes

• Cash flow

Government Purchases

• Federal spending rises during downturns and military escalations

• State/local spending may fall due to balanced budget requirements

Net Exports

• Relative inflation rates

• Relative GDP growth rates

• Exchange rates