Macroeconomics Study Notes: GDP, Inflation & Unemployment, Aggregate Expenditures, and AD/AS Models

Topic 5: GDP

Definition and Calculation of GDP

Gross Domestic Product (GDP) is the total market value of all final goods and services produced within a country in a given period. It is a key indicator of economic activity and growth.

• Three Methods of Calculating GDP:

  • Expenditure Approach: Sums all expenditures made in the economy (consumption, investment, government spending, net exports).

  • Output (Production) Approach: Sums the value added at each stage of production.

  • Income Approach: Sums all incomes earned by factors of production (wages, rents, interest, profits).

• GDP and Business Cycle: GDP fluctuates with expansions (growth) and recessions (decline).

• Final Goods vs. Intermediate Goods: Only final goods are included in GDP to avoid double counting.

• Limitations of GDP: GDP does not measure well-being, non-market activities, or income distribution.

• Types of GDP:

  • Nominal GDP: Measured at current market prices.

  • Real GDP: Adjusted for inflation, measured at constant prices.

  • GDP Growth Rate: Percentage change in real GDP over time.

  • GDP Deflator: A price index used to adjust nominal GDP to real GDP.

Formula Examples:

• Expenditure Approach: $GDP = C + I + G + (X - M)$

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

• Real GDP Growth Rate: $\text{Growth Rate} = \frac{Real\ GDP_{t} - Real\ GDP_{t-1}}{Real\ GDP_{t-1}} \times 100$

Example: If nominal GDP is $1,000$ and real GDP is $900$, the GDP deflator is$\frac{1000}{900} \times 100 = 111.1$.

Topic 6: Inflation and Unemployment

Types and Measurement of Unemployment

Unemployment measures the share of the labor force without jobs but actively seeking work. It is a key indicator of economic health.

• Types of Unemployment:

  • Frictional: Short-term, occurs when people are between jobs.

  • Structural: Caused by changes in the economy, such as technological advances.

  • Cyclical: Related to the business cycle, rises during recessions.

• Natural Rate of Unemployment: The sum of frictional and structural unemployment; the lowest sustainable rate.

• Labor Force Participation Rate (LFPR): $LFPR = \frac{Labor\ Force}{Population\ over\ 16}$

• Unemployment Rate: $Unemployment\ Rate = \frac{Unemployed}{Labor\ Force} \times 100$

Measurement of Inflation

• Consumer Price Index (CPI): Measures average change in prices paid by consumers for a basket of goods and services.

• Calculating Inflation Rate: $Inflation\ Rate = \frac{CPI_{t} - CPI_{t-1}}{CPI_{t-1}} \times 100$

• Nominal vs. Real Values: Nominal values are not adjusted for inflation; real values are.

• Adjusting for Inflation: Real value = $\frac{Nominal\ Value}{CPI/100}$

• Interest Rates: Real interest rate = $Nominal\ Rate - Inflation\ Rate$

• Unexpected Inflation: Can benefit borrowers and hurt lenders.

Example: If the CPI increases from 200 to 210, the inflation rate is $\frac{210-200}{200} \times 100 = 5\%$.

Topic 7: The Aggregate Expenditures Model

Consumption Function and Macroeconomic Equilibrium

The Aggregate Expenditures Model explains how total spending determines output and income in the short run. It is central to Keynesian economics.

• Consumption Function: Shows the relationship between consumption and disposable income.

  • General form: $C = a + bY_d$ where $a$ is autonomous consumption, $b$ is marginal propensity to consume (MPC), and $Y_d$ is disposable income.

• Components of Aggregate Expenditures: Consumption (C), Investment (I), Government Spending (G), Net Exports (X-M).

• Macroeconomic Equilibrium: Occurs when aggregate expenditures equal output (Y): $AE = Y$.

• Multiplier Effect: Shows how an initial change in spending leads to a larger change in output: $Multiplier = \frac{1}{1 - MPC}$

• Autonomous Spending: Spending not influenced by current income.

• Government Policy: Fiscal policy can shift aggregate expenditures and affect equilibrium.

Example: If MPC = 0.8, the multiplier is $\frac{1}{1-0.8} = 5$.

Topic 8: Aggregate Demand/Aggregate Supply Model

AD/AS Curves and Economic Fluctuations

The AD/AS model illustrates the interaction between aggregate demand and aggregate supply, determining the overall price level and output in the economy.

• Aggregate Demand (AD) Curve: Shows the total quantity of goods and services demanded at different price levels.

• Movement vs. Shift:

  • Movement: Caused by changes in the price level.

  • Shift: Caused by changes in components of AD (C, I, G, X-M).

• Aggregate Supply (AS) Curve:

  • Short Run AS (SRAS): Upward sloping due to sticky wages and prices.

  • Long Run AS (LRAS): Vertical at full employment output; not affected by price level.

• Sticky Prices: Prices and wages that do not adjust immediately to changes in economic conditions.

• Economic Shocks: Events that shift AD or AS, such as changes in consumer confidence, fiscal policy, or supply disruptions.

• Adjustment to Shocks:

  • Short run: Output and employment may change.

  • Long run: Economy returns to full employment as prices and wages adjust.

Curve	Shape	What Shifts It?
AD	Downward sloping	Changes in C, I, G, X-M
SRAS	Upward sloping	Input prices, productivity, expectations
LRAS	Vertical	Technology, resources, institutions

Example: A negative supply shock (e.g., oil price spike) shifts SRAS left, raising prices and reducing output in the short run.