Circular Flow of Income & Wealth
— Economics · Macroeconomics · Feb/March 2023 P2 V2 —
★ Exam Tip: This is an 8-mark essay: K → 3 marks, A → 3 marks, E → 2 marks. Don't just describe the flow — you must also judge the extent to which it changes when the economy becomes open.
1. The Question & Plan
Feb/March 2023 · P2 V2 · Q1Essay · 8 marks
Explain the circular flow of income and consider the extent to which the circular flow of income changes as an economy becomes an open economy. (8)
Marks: K → 3M · A → 3M · E → 2M
Underlined on board: extent, changes, economy becomes an open economy ⇒ the answer is about the CHANGE closed → open.
How to start the answer (plan)
- Define Circular Flow of Income → mention players, equilibrium, withdrawals, injections
- Define Macro Economic Equilibrium → Y = AE and W = J
- Define Closed Economy / Open Economy
2. Macro Economic Equilibrium
Definition: Macro-economic equilibrium is the point where income = aggregate expenditure.
Y = AE
Income side (Y)Income (Y) = Consume + Save + Tax + Import
Expenditure side (AE)AE = Consumption Exp + Investment Exp + Govt Exp + Export Revenue
Expenditure side (AE)AE = Consumption Exp + Investment Exp + Govt Exp + Export Revenue
Income = Leakages = Withdrawals (W)
AE = Investment = Injections (J)
W = J
AE = Investment = Injections (J)
W = J
Key terms: Withdrawal / leakage (W) = any deduction from income ·
Injection (J) = money put back into the economy (investment) · Players = sectors in the flow
| Withdrawals (W) — leave the flow | Injections (J) — enter the flow |
|---|---|
| Saving (S) → banks | Investment expenditure (I.E.) ← banks' loans |
| Tax (T) → government | Government expenditure (G.E.) — roads & development |
| Import (M) → abroad | Export revenue (X / E.R.) ← abroad |
3. Types of Sector Economy
Add one sector at a time: each new player brings one withdrawal and one injection. Every type stays in equilibrium: Y = AE and W = J.
① 2-Sector Closed Economy
2 players → Households and Firms · consume (W) · C.E. (J)
Y = AE
C = C.E.
W = J
C = C.E.
W = J
Note: C.E. = consumer expenditure. Here all income is spent, so there is no saving, tax or import — consumption matches consumer expenditure.
② 2-Sector Open Economy
3 players → Households, Firms / Banks · save (W) · I.E. (J) (loans)
Y = AE
C + S = C + I
W = J
C + S = C + I
W = J
③ 3-Sector Economy (Closed)
4 players → Households, Firms, Banks, Government · tax (W) · G.E. (J) (roads)
Y = AE
C + S + T = C + I + G
S + T = I + G
W = J
C + S + T = C + I + G
S + T = I + G
W = J
④ 4-Sector Economy (Open)
5 players → Households, Firms, Banks, Government, Abroad (Foreign sector) · Import (W) · Export (J)
Y = AE
Consume + Save + Tax + Import = C.E. + I.E. + G.E. + E.R.
C + S + T + M = C + I + G + X
cancel C on both sidesS + T + M = I + G + X
W = J
Consume + Save + Tax + Import = C.E. + I.E. + G.E. + E.R.
C + S + T + M = C + I + G + X
cancel C on both sidesS + T + M = I + G + X
W = J
| Type | Closed / Open | Players | W | J | Equilibrium |
|---|---|---|---|---|---|
| 2-sector | closed | 2 | consume | C.E. | C = C.E. |
| 2-sector | open | 3 | save | I.E. | C+S = C+I |
| 3-sector | closed | 4 | save, tax | I.E., G.E. | C+S+T = C+I+G |
| 4-sector | open | 5 | save, tax, import | I.E., G.E., export | C+S+T+M = C+I+G+X |
4. Why Closed / Why Open?
Board questionShort answer
Why is a 3-sector economy a closed economy, and why is a 4-sector economy an open economy?
3-sector = closed → country is not open to international trade → no foreign sector.
4-sector = open → economy is open to international trade → foreign sector (abroad) added.
Closed = no trade with abroad · Open = trade with abroad
Remember: the ONLY difference between ③ and ④ is the Abroad sector — import (W) and export (J).
5. Effects of Changing from Closed to Open
The new player Abroad adds imports (withdrawal) and exports (injection) to the 3-sector flow.
| Closed (3-sector) | Open (4-sector) | |
|---|---|---|
| Players | 4 | 5 (+ Abroad) |
| Income (Y) = | C + S + T (3 parts) | C + S + T + M (4 parts) |
| AE = | C + I + G (3 parts) | C + I + G + X (4 parts) |
| W = J | S + T = I + G | S + T + M = I + G + X |
Conclusion (evaluation): the importance of X − M and the
percentage of GDP's size decide the extent of the change.
Exports are always an injection and imports are always a withdrawal — but the impact depends on the size of exports & imports and on the % of GDP.
Exports are always an injection and imports are always a withdrawal — but the impact depends on the size of exports & imports and on the % of GDP.
6. Model Answer (as written on board)
① Introduction — definitions
Circular flow of income & wealth shows different sector economies, each with different players adding
withdrawals and injections.
Macro equilibrium is the point where income = aggregate expenditure: Y = AE.
Any deduction from income is a leakage / withdrawal; money put into the economy as investment is an injection.② Closed economy (3-sector, 4 players)
Players: households, firms, banks, government. Households own factors of production → given to firms; in return they get
payments = their income. Income is not all spent: some is saved in banks and some is paid as tax to government
→ these are leakages (withdrawals).Savings → bank funds → passed to firms as loans = investment = injection
Tax → government funds → roads & development = government expenditure = injection
So Income has 3 components (consumption, saving, taxation) and AE has 3 (consumption, investment, government expenditure) → macro equilibrium.
③ Open economy (4-sector)
One more sector is added: the foreign sector with exports and imports → adds a withdrawal and an injection.
Income now has 4 components: consumption, saving, taxation, import.
AE has: consumption, investment, government expenditure, export revenue.
In an open economy savings + taxation + imports = investment + G.E. + export revenue, i.e. withdrawals = injections → macro equilibrium.④ Conclusion — "to what extent"
In my opinion, even in an open economy exports will always be added as an injection and imports will always be deducted
as a withdrawal from income, but the impact depends on the size of exports and imports and on the percentage of GDP.✓ Quick Recap — Circular Flow of Income
- Macro equilibrium: Y = AE and W = J
- Y = C + S + T + M · AE = C + I + G + X
- Withdrawals (W): save, tax, import — Injections (J): I.E., G.E., exports
- 2-sector closed (2 players): C = C.E. · 2-sector open (3): C + S = C + I
- 3-sector closed (4 players): S + T = I + G
- 4-sector open (5 players): S + T + M = I + G + X
- Closed = no international trade · Open = trade with abroad (foreign sector)
- Evaluation: importance of X − M · % of GDP's size