Ch4. Introduction to Macroeconomics — GDP, National Income, Prices, and Inflation
What Is Macroeconomics?
Macroeconomics analyzes the economy as a whole rather than individual agents.
Core questions:
- How do we measure an economy’s total output (GDP)?
- Why do prices rise? (Inflation)
- Why does unemployment exist?
- How does economic growth occur?
- How do governments and central banks manage the business cycle?
Macroeconomics is the toolkit for policymakers (governments, central banks) and a core subject in economics coursework worldwide.
GDP (Gross Domestic Product)
GDP is the total market value of all final goods and services produced within a country’s borders during a given period (usually one year).
Three Approaches to Measuring GDP
1. The Expenditure Approach (most widely used)
GDP = C + I + G + NX
| Component | Content |
|---|---|
| C (Private Consumption) | Household spending on goods and services |
| I (Investment) | Business equipment and inventories, residential construction |
| G (Government Spending) | Government purchases of goods and services (excludes transfer payments) |
| NX (Net Exports) | Exports − Imports |
2. The Income Approach: Sum of wages, interest, rent, and profits earned in production
3. The Production Approach: Sum of value added across all industries
All three approaches should yield identical results in theory (the national income identity).
Nominal GDP vs. Real GDP
Nominal GDP: GDP measured at current prices
Real GDP: GDP measured at base-year prices (removes the effect of price changes)
GDP Deflator = (Nominal GDP / Real GDP) × 100
| Year | Nominal GDP | Real GDP (2020 base) |
|---|---|---|
| 2020 | $21.4T | $21.4T |
| 2024 | $28.6T | $25.1T |
→ In this example, actual economic growth is roughly 17%, while the remainder reflects price-level increases.
Per Capita GDP: GDP ÷ Population. Widely used to compare living standards. However, it does not reflect income inequality, leisure, or environmental quality.
National Income Accounts
| Measure | Description |
|---|---|
| GDP | Production within national borders |
| GNP | Production by a country’s nationals (regardless of location) |
| NNP | GNP − Depreciation |
| NI (National Income) | NNP − Indirect taxes + Subsidies |
| PI (Personal Income) | NI − Corporate taxes and retained earnings + Transfer payments |
| DI (Disposable Income) | PI − Personal income taxes |
DI (Disposable Income) is what households actually spend on consumption and saving.
Price Levels and Inflation
Price Indices
Consumer Price Index (CPI): Measures price changes of a representative basket of goods and services purchased by urban households.
GDP Deflator: Measures price changes of all goods and services included in GDP.
Producer Price Index (PPI): Measures price changes in business-to-business transactions. Used as a leading indicator for CPI.
Inflation rate = (This year’s CPI − Last year’s CPI) / Last year’s CPI × 100
Causes of Inflation
Demand-Pull Inflation: Aggregate demand exceeds aggregate supply → prices rise. Occurs during economic overheating.
Example: Surge in government spending + excess money supply → demand jumps → prices rise
Cost-Push Inflation: Rising production costs reduce supply → prices rise. The cause of stagflation (recession + inflation).
Example: The 1973 oil embargo → production costs surge → prices rise
Quantity Theory of Money (Monetarist View): MV = PQ (M: money supply, V: velocity, P: price level, Q: real output) → When money supply increases, prices rise in the long run
Effects of Inflation
Debtors vs. Creditors: Inflation erodes the real value of debt, benefiting borrowers and hurting lenders.
Real Wage Decline: If nominal wages are unchanged, rising prices reduce real purchasing power.
Resource Misallocation: Increased uncertainty discourages business investment and complicates long-term planning.
Hyperinflation: Currency collapse and reversion to barter. Historical examples: Weimar Germany (1923), Zimbabwe (2008).
Unemployment
Unemployment rate = Number of unemployed / Labor force × 100
Labor force = Employed + Unemployed (persons 16 and older who are willing and able to work)
Those not in the labor force (students, stay-at-home parents, discouraged workers) are excluded, which can understate the true unemployment situation.
Types of Unemployment
| Type | Description | Example |
|---|---|---|
| Frictional | Temporary unemployment during job transitions | Searching for work after quitting |
| Structural | Skills mismatch due to technological or industrial change | Jobs displaced by automation |
| Seasonal | Demand fluctuations by season | Construction or agriculture off-season |
| Cyclical | Reduced demand during recessions | Layoffs in a downturn |
Natural rate of unemployment: Frictional + structural unemployment only. The ideal state in which there is no cyclical unemployment. Full employment = natural rate of unemployment.
The Phillips Curve
The Phillips Curve depicts the short-run inverse (−) relationship between inflation and unemployment.
- Low unemployment → high labor demand → rising wages → higher inflation
- High unemployment → low labor demand → stable wages → lower inflation
Policy dilemma: Reducing inflation tends to raise unemployment, and reducing unemployment tends to raise inflation.
Long-run Phillips Curve: Vertical. The economy converges to the natural rate of unemployment regardless of the inflation rate. The short-run trade-off disappears in the long run.
Stagflation: After the 1970s oil shocks, high inflation and high unemployment occurred simultaneously → the Phillips Curve shifted outward to the right.
Learning Checklist
- Explain the three approaches to measuring GDP
- Explain each component of GDP = C + I + G + NX
- Explain the difference between nominal and real GDP
- Distinguish demand-pull from cost-push inflation
- Describe all four types of unemployment with examples
- Explain the short-run and long-run Phillips Curve relationship
Key Concept Cards
Production Function Q = f(K, L) ★★★ : A function showing maximum output (Q) from inputs capital (K) and labor (L). Short run: K fixed, L variable. Long run: all inputs variable.
Law of Diminishing Marginal Product (DMPL) ★★★★ : In the short run, adding more of the variable input (labor) eventually decreases marginal product. MP = ΔQ/ΔL.
Economies of Scale vs. Diseconomies of Scale ★★★★★ : Economies of scale: output ↑ → long-run average cost (LRAC) ↓. Diseconomies: output ↑ → LRAC ↑. Constant returns to scale (CRS): LRAC flat. Natural monopoly: extreme economies of scale (very high fixed costs). Memory tip: LRAC U-shape: left side = economies of scale, right side = diseconomies of scale
Cost Structure: TC = FC + VC ★★★★★ : Total cost (TC) = Fixed cost (FC) + Variable cost (VC). MC = ΔTC/ΔQ = ΔVC/ΔQ. ATC = TC/Q. When MC < ATC, ATC falls; when MC > ATC, ATC rises. MC intersects ATC at ATC’s minimum (the shutdown point and above).
Isoquant–Isocost Equilibrium ★★★★ : Producer optimum: MRTS (labor-capital) = factor price ratio (w/r), i.e., MPL/MPK = w/r. The production-side analog of consumer equilibrium.
Practice Quiz
Q. What are the conditions for the short-run shutdown point and the long-run exit point?
Short-run shutdown: P < AVC (cannot even cover variable costs). Long-run exit: P < ATC (cannot cover total costs).
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