Topic 2.1 Notes – The Circular Flow and GDP

1. Gross Domestic Product

GDP is the dollar value of all final goods and services produced within a country’s borders in one year.

Break that definition apart carefully:

• Final goods and services
  Only goods sold to the end user.
  A tire used to make a car is an intermediate good. The car is the final good. Counting both would be double counting.
• Produced
  Must be current production. A used car sold this year was produced in a past year, so it doesn’t count again.
• Within a country’s borders
  Production inside the U.S. counts in U.S. GDP, even if the firm is foreign-owned. A Toyota made in Kentucky counts toward U.S. GDP.
• In one year
  GDP is a flow variable. It measures output per year, not total wealth.

GDP Measures Output and Income

Every dollar spent becomes someone else’s income.
When you buy a 30-dollar haircut, the barber receives 30 dollars in income.

So:

Total spending = Total income = Total output

That identity is the heart of this topic.

2. The Circular Flow Model

The circular flow shows why spending equals income.

The circular flow of households, firms, and markets

There are two key players:

• Households (consumers, resource owners)
• Firms (producers)

And two markets:

Product Market

• Firms sell goods and services
• Households buy them
• Money flows households → firms
• Goods and services flow firms → households

Factor (Resource) Market

• Households sell resources (labor, land, capital, entrepreneurship)
• Firms buy resources
• Money flows firms → households (wages, rent, interest, profit)
• Resources flow households → firms

This is based on voluntary exchange. Both sides choose to trade because they expect to benefit.

If you work at a grocery store:

• You sell labor in the factor market and earn wages.
• You spend those wages in the product market.

The money just keeps circulating. That’s why measuring total spending gives the same result as measuring total income.

3. The Three Ways to Measure GDP

All three approaches should produce the same number.

1. Expenditures Approach

$$\text{GDP} = C + I + G + (X - M)$$

This is the most tested formula.

• C (Consumption)
  Household spending on goods and services
  Includes durable goods, nondurables, and services.
• I (Investment)
  Business spending on capital
  • Equipment, factories
  • New residential construction
  • Changes in inventories
  Stocks and bonds do not count.
• G (Government Spending)
  Government purchases of goods and services
  Military equipment and highways count.
  Transfer payments like Social Security or unemployment benefits do not.
• Net Exports (X − M)
  Exports add.
  Imports subtract because they were not produced domestically.

Quick Calculation Practice

Suppose:

• C = 900 billion
• I = 250 billion
• G = 300 billion
• Exports = 120 billion
• Imports = 170 billion

Net exports = $120 - 170 = -50$

GDP = $900 + 250 + 300 - 50 = 1{,}400$ billion

Always subtract imports.

2. Income Approach

Adds up income earned from production:

• Wages
• Rent
• Interest
• Profit

Since spending becomes income, this must equal the expenditure total.

3. Value-Added Approach

Adds the value added at each stage of production.

Value added = Sales revenue − Cost of intermediate goods

This avoids double counting and ensures only final output is included.

4. What Is Not Included in GDP

Common test traps:

• Intermediate goods
• Used goods
• Financial transactions (stocks, bonds)
• Transfer payments
• Unpaid work (volunteering, stay-at-home parenting)
• Illegal activities
• Depreciation (wear and tear)

If it’s not new, final production this year inside the country, it doesn’t count.