Macroeconomics Study Guide: Aggregate Expenditures, Economic Growth, Unemployment, and Inflation

Chapter 8: Aggregate Expenditures and Equilibrium GDP

Actual Real GDP in the Short Run

Understanding real GDP in the short run is essential for analyzing economic fluctuations and policy impacts.

• Definition: Real GDP measured in the short run may differ from potential GDP due to price and wage inflexibility.

• Price/Wage Rigidity: Prices and wages are sticky in the short run, meaning they do not adjust immediately to changes in demand. This can cause temporary unemployment or inflation.

Components of Aggregate Expenditures (AE)

Aggregate expenditures represent the total spending in the economy and determine the equilibrium level of GDP.

• Formula: $AE = C + I + G + NX$

• C: Consumption

• I: Investment

• G: Government spending

• NX: Net exports (Exports – Imports)

Planned vs. Unplanned AE

Distinguishing between planned and unplanned aggregate expenditures helps explain inventory changes and business cycles.

• Planned AE: Total spending households, businesses, government, and foreign buyers intend to make.

• Unplanned AE: Occurs when actual spending differs from planned (e.g., unexpected inventory changes).

Disposable Income (DI)

Disposable income is the income available to households after taxes, influencing consumption and saving decisions.

• Formula: $DI = GDP - T$

• Consumption (C) + Saving (S): $DI = C + S$

• Marginal Propensity to Consume (MPC): Fraction of additional DI spent on consumption.

• Marginal Propensity to Save (MPS): Fraction of additional DI saved.

• Relationship: $MPC + MPS = 1$

Consumption Function (CF)

The consumption function models the relationship between disposable income and consumption.

• Formula: $C = a + MPC \times DI$

• a: Autonomous consumption (spending even if DI = 0)

• Slope: MPC

• Saving and Dissaving: Occurs when consumption exceeds DI.

AE Function

The aggregate expenditure function can be modified to include government and trade.

• Without government and trade: $AE = C + I$

• Adding Government (G, T): $AE = C + I + G$

• Adding Net Exports (NX): $AE = C + I + G + NX$

• Vertical Intercept: Increases with autonomous G or X.

• Slope: Decreases with imports (reduces induced expenditures).

Equilibrium GDP

Equilibrium GDP occurs where aggregate expenditures equal output, determining the actual level of economic activity.

• Graphically: Where AE line intersects 45° line (AE = GDP).

• Numerical Formula: $\Delta Y = \text{Multiplier} \cdot \Delta \text{Autonomous Expenditure}$

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

• With taxes/imports: Adjust slope to account for marginal tax rate and import propensity.

Inventories and Disequilibrium

Inventory changes signal disequilibrium in the goods market, prompting firms to adjust production.

• Excess AE: Inventories fall → Firms increase production → GDP rises.

• AE < GDP: Inventories rise → Firms cut production → GDP falls.

Chapter 10: Economic Growth and Labor Markets

Economic Growth

Economic growth refers to the increase in real GDP over time, often measured at full employment.

• Potential GDP: Level of real GDP produced at full employment.

• Rule of 70: Estimate years to double GDP: $\text{Years to double} = \frac{70}{\text{growth rate} (\%)}$

Aggregate Production Function

The aggregate production function shows how inputs are transformed into output (real GDP).

• Formula: $Y = F(L, K, H, T)$

• L: Labor

• K: Physical capital

• H: Human capital

• T: Technology

• Law of Diminishing Returns: Each additional unit of labor adds less output if other inputs are fixed.

Labor Productivity Factors

Labor productivity is determined by the quality and quantity of inputs.

• Physical Capital

• Human Capital (skills, education)

• Technology

Labor Market

The labor market determines employment and wage levels through supply and demand.

• Aggregate Labor Demand (LD): Derived from the marginal product of labor.

• Labor Supply (LS): Determined by opportunity cost of time and income effect.

Labor Market and Growth

Population and productivity changes affect the labor market and potential GDP.

• Population Increase: Shifts LS → Potential GDP rises.

• Productivity Increase: Shifts LD → Potential GDP rises.

Chapter 13: Unemployment and Inflation

Labor Market Measures

Key labor market indicators help assess the health of the economy.

• Working-Age Population: People 16+ able to work.

• Labor Force: Employed + Unemployed (actively seeking).

• Employment-to-Population Ratio: $\frac{\text{Employed}}{\text{Working-age population}} \times 100$

• Labor Force Participation Rate: $\frac{\text{Labor Force}}{\text{Working-age population}} \times 100$

• Aggregate Hours: Total hours worked in economy.

Types of Unemployment

Unemployment is classified by its causes, which affect policy responses.

• Frictional: Between jobs.

• Structural: Skills mismatch or geographic mismatch.

• Cyclical: Due to recessions.

Wage Measures

Wages can be measured in nominal or real terms to account for inflation.

• Nominal Wage: Current dollar wage.

• Real Wage: Adjusted for inflation.

Chapter 14: Price Levels and Inflation

Measuring Price Level

Price indices track changes in the cost of goods and services over time.

• Consumer Price Index (CPI): Tracks cost of typical consumption basket.

• Producer Price Index (PPI): Tracks cost of goods at producer level.

• GDP Deflator: Price index for all domestically produced final goods.

Calculating CPI

The CPI is calculated using a basket of goods and services, comparing costs over time.

1. Consumer Expenditure Survey: Identify goods/services.

2. Vendors' Survey: Get prices.

3. Base Period: CPI = 100.

4. Other Years: $CPI_t = \frac{\text{Cost of basket at current year prices}}{\text{Cost of basket at base year prices}} \times 100$

Inflation Rate

Inflation rate measures the percentage change in price level over time.

• Formula: $\text{Inflation rate} = \frac{CPI_t - CPI_{t-1}}{CPI_{t-1}} \times 100$

Economic Costs of Inflation

Inflation imposes various costs on the economy, affecting efficiency and distribution.

• Wealth Redistribution: Borrowers vs. lenders.

• Resource Diversion: More time spent on hedging or adjusting contracts rather than production.

Formulas to Remember

Formula	Description
$AE = C + I + G + NX$	Aggregate Expenditures
$DI = GDP - T$	Disposable Income
$MPC + MPS = 1$	Marginal Propensity to Consume/Save
$\text{Multiplier} = \frac{1}{1 - MPC}$	Simple Multiplier
$\text{Inflation Rate} = \frac{CPI_t - CPI_{t-1}}{CPI_{t-1}} \times 100$	Inflation Rate
$\text{Years to double} = \frac{70}{\text{growth rate} (\%)}$	Rule of 70