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National Income Model Answers

Section 2.3.4 — Annotated model answers for the circular flow of income, injections, withdrawals, and the multiplier.

These model answers demonstrate how to structure responses for Edexcel International A-Level (IAL) Economics and Business exams. Each answer includes a mark scheme breakdown, PEEL structure (where applicable), annotated paragraphs, and examiner commentary explaining what earns marks at each band.
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8 marks
Unit 2 · 2.3.4 National Income · Analysis
Analyse: how the circular flow of income model shows the impact of injections and withdrawals on national income.
Mark Scheme Breakdown
1–2 marksKnowledge: definition of circular flow model, injections and/or withdrawals
3–4 marksApplication: identification of specific injections (I, G, X) and withdrawals (S, T, M) with examples
5–8 marksAnalysis: developed chain — when injections exceed withdrawals, national income rises via multiplier; when withdrawals exceed injections, it contracts
PEEL Structure
P
Point

The circular flow model illustrates how injections and withdrawals determine the level of national income.

E
Evidence

E.g. government spending on the NHS adds income to the circular flow; saving by households withdraws income from it.

E
Explain

When injections (I + G + X) exceed withdrawals (S + T + M), national income rises through the multiplier effect. When withdrawals exceed injections, national income contracts.

L
Link

This framework helps explain why changes in government spending, investment, or trade balances cause fluctuations in GDP.

KKnowledge
AApplication
AnAnalysis chain
Model Answer
Para 1
The circular flow of income model shows how money flows between households and firms in an economy. K Households provide factors of production (land, labour, capital, enterprise) to firms and receive factor incomes (rent, wages, interest, profit) in return. Households then spend this income on goods and services produced by firms, completing the flow. K
Para 2
Injections are additions to the circular flow that increase national income. They consist of investment (I) by firms, government spending (G), and export revenue (X). K For example, government spending on the NHS pays wages to doctors and nurses, adding income to the flow. A Withdrawals (or leakages) are removals from the circular flow: saving (S), taxation (T), and import spending (M). K When households save rather than spend, that income does not flow back to firms, reducing overall economic activity. An
Para 3
When injections exceed withdrawals (I + G + X > S + T + M), national income rises. An This increase is amplified by the multiplier effect — an initial injection of spending generates successive rounds of income and re-spending. For example, a £1bn increase in government infrastructure spending creates jobs and wages, which are partly re-spent on goods and services, creating further income for other firms and workers. A Conversely, when withdrawals exceed injections, national income contracts — firms receive less revenue, reduce output, and may lay off workers, leading to a negative multiplier effect. An The economy reaches equilibrium when total injections equal total withdrawals, and national income is stable. An
Examiner Commentary

This answer builds a developed chain: define model → identify injections and withdrawals → explain the multiplier mechanism → show how imbalance causes changes in national income. The NHS and infrastructure examples provide concrete application. For top marks, candidates should reference the equilibrium condition (injections = withdrawals) and the multiplier effect. A clearly labelled circular flow diagram would earn additional credit.

Likely Score7–8 / 8
8 marks
Unit 2 · 2.3.4 National Income · Analysis
Analyse: how the multiplier effect works and why the multiplier may be smaller than expected.
Mark Scheme Breakdown
1–2 marksKnowledge: definition of multiplier, formula (1/(1-MPC))
3–4 marksApplication: numerical example or real-world context
5–8 marksAnalysis: rounds of spending, leakages reducing the multiplier, reasons for smaller-than-expected effect
PEEL Structure
P
Point

An initial injection of spending creates successive rounds of income and expenditure, magnifying the impact on GDP.

E
Evidence

E.g. the UK government's £400bn COVID support packages aimed to stimulate the economy via the multiplier.

E
Explain

Each round of spending generates income, but leakages (savings, taxes, imports) remove money from the circular flow, so each round is smaller than the last.

L
Link

The size of the multiplier depends on the marginal propensity to consume — in an open economy with high taxes and import spending, the multiplier is much smaller.

KKnowledge
AApplication
AnAnalysis chain
Model Answer
Para 1
The multiplier effect describes how an initial change in spending leads to a larger final change in national income. K The multiplier is calculated as 1 / (1 – MPC), where MPC is the marginal propensity to consume. If MPC = 0.8, the multiplier is 5 — an initial £1bn injection leads to a £5bn increase in GDP. K
Para 2
The mechanism works through successive rounds of spending. When the government invests £1bn in infrastructure, construction workers receive income. A If their MPC is 0.8, they spend £800m — which becomes income for retailers, suppliers, and service providers. Those recipients then spend 80% of their new income (£640m), and so on. An Each round generates new income, creating a cumulative increase far larger than the initial injection. An
Para 3
However, the multiplier is often smaller than theory suggests because of leakages from the circular flow. An In each round, income leaks out through savings (reducing re-spending), taxation (government takes a share), and imports (spending on foreign goods does not generate domestic income). An In an open economy like the UK — with high income tax, high import penetration, and a modest savings rate — the multiplier may be closer to 1.3–1.5 rather than the theoretical 5. A Additionally, if the economy is near full capacity, extra spending may cause inflation rather than increasing real output, further reducing the effective multiplier. An
Examiner Commentary

Strong answer that explains both the mechanism and its limitations. The numerical walkthrough (£1bn → £800m → £640m) makes the chain concrete. The distinction between theoretical and practical multiplier values (5 vs 1.3–1.5) is exactly what earns top marks. The point about inflation at full capacity shows evaluative awareness.

Likely Score7–8 / 8

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