4.2 - Introduction to the Circular Flow of Income
The basic circular flow of income model
The circular flow of income model illustrates how money, goods, and services move between different parts of an economy. It shows the continuous cycle where output creates income, which is then used to buy more output. This explains why gross domestic product (GDP) can be calculated using three methods: total output produced, total income earned, or total expenditure on goods and services.
Types of economies in the circular flow model
- Closed economy - An economy that does not engage in international trade, with no imports or exports of goods and services.
- Open economy - An economy that participates in international trade, including both imports and exports.
Components of the circular flow model
The model consists of two main flows that connect households and firms:
- Inner circle (real flow) - Represents the physical exchange of goods and services, including:
- Products (goods and services) flowing from firms to households.
- Factor services flowing from households to firms, such as labour, capital, entrepreneurship, and land.
- Outer circle (money flow) - Represents the financial exchanges, including:
- Spending by households on goods and services from firms.
- Incomes paid by firms to households as factor payments, such as wages (for labour), interest (for capital), profit (for entrepreneurship), and rent (for land).
Injections and leakages in the circular flow
Injections and leakages (also known as withdrawals) are flows that either add to or remove money from the circular flow, affecting the overall level of economic activity. Injections increase spending in the economy, while leakages reduce it.
The main types of injections
- Investment (I) - Spending by firms on capital goods, which adds to the flow.
- Government spending (G) - Expenditure by the government, boosting economic activity.
- Exports (X) - Sales of goods and services to foreign buyers, bringing money into the economy from abroad.
The main types of leakages
- Saving (S) - Money set aside by households or firms rather than spent, removing it from the flow.
- Taxation (T) - Payments to the government, which reduce available spending.
- Imports (M) - Purchases of goods and services from abroad, sending money out of the economy.
Equilibrium in two-sector and four-sector economies
Economic equilibrium in the circular flow occurs when total injections equal total leakages, leading to a stable level of income and output. If injections exceed leakages, extra spending boosts income; if leakages exceed injections, reduced spending lowers income.
Two-sector economy equilibrium
A two-sector economy includes only households and firms, with no government or international trade. Equilibrium is achieved when saving equals investment (S = I).
How equilibrium changes:
- A rise in investment increases GDP by adding more spending to the flow.
- An increase in saving can lead to unsold products, causing firms to reduce production and lower GDP.
Four-sector economy equilibrium
A four-sector economy includes households, firms, government, and international trade.
Where:
- I = Investment
- G = Government spending
- X = Exports
- S = Saving
- T = Taxation
- M = Imports
Factors affecting equilibrium income levels
Changes in injections or leakages can shift the economy to a new equilibrium level of income. In the short run, these adjustments affect GDP directly.
Changes that increase equilibrium income
- A rise in injections, such as higher investment or exports, adds spending and pushes income upwards.
- A fall in leakages, such as reduced saving or lower imports, leaves more money in the flow, increasing income.
Changes that decrease equilibrium income
- Higher tax rates reduce disposable income available for spending, lowering equilibrium.
- Increased saving or imports withdraw more money from the flow, causing GDP to fall in the short run.
Long-run relationships between injections and leakages
Over time, changes in injections and leakages are interconnected, as initial increases in injections can lead to matching rises in leakages, restoring equilibrium at a higher level.
How injections and leakages adjust in the long run
- Investment and saving - Higher investment boosts incomes, leading to increased saving; in turn, more saving can fund further investment.
- Government spending and taxation - Extra government spending raises incomes, generating higher tax revenue through economic growth.
- Exports and imports - Growth in exports increases incomes, which can lead to more spending on both domestic goods and imports.
- Time factor - An initial injection raises GDP, but over time, leakages increase to match the new level of injections, stabilising the economy.