1 · Consumer behaviour and markets
marginal benefit · equilibrium
U1-Q1 · 2 marks
At P = 10, which imbalance occurs?
Answer and reasoning · 答案与解析
Qd = 100 and Qs = 50, so excess demand is 50.
U1-Q2 · 4 marks
Explain the mechanism or reasoning in this original case: A commuter keeps buying a familiar ticket despite a cheaper option. The market model is useful, but assumptions about rational choice need checking.
Answer and reasoning · 答案与解析
Demand is Qd = 120 − 2P and supply is Qs = 20 + 3P. Set Qd = Qs: 120 − 2P = 20 + 3P. Then 100 = 5P, P = 20 and Q = 80. Check both equations before drawing the intersection.
- Accurate relevant concept (1)
- Specific evidence from the case (1)
- Connected reasoning (2)
An algebraic equilibrium is conditional on the functions and other factors staying constant. / A supply shift does not shift demand: it changes equilibrium through movement along the existing demand curve.
2 · Market failure and policy
public good · government failure
U2-Q1 · 2 marks
Which condition identifies the efficient output in the simple externality model?
Answer and reasoning · 答案与解析
Marginal social benefit equals marginal social cost.
U2-Q2 · 4 marks
Explain the mechanism or reasoning in this original case: Drivers choose routes using their own journey cost while adding delays for other users. A private optimum can differ from the social optimum.
Answer and reasoning · 答案与解析
A congestion charge can raise the private cost of peak journeys. If drivers respond, journeys and delays fall. Compare the charge with public transport investment: one discourages journeys, the other improves alternatives.
- Accurate relevant concept (1)
- Specific evidence from the case (1)
- Connected reasoning (2)
A transfer of tax revenue is not itself a social resource cost. / Policy evaluation should consider the size of the externality, enforcement costs, equity and unintended effects.
3 · National income and aggregate activity
multiplier · real GDP
U3-Q1 · 2 marks
What happens to the simple multiplier when the marginal propensity to save rises?
Answer and reasoning · 答案与解析
It falls because more of each extra unit of income leaks from spending.
U3-Q2 · 4 marks
Explain the mechanism or reasoning in this original case: A country reports higher GDP, but its population and prices also grew. The headline increase alone does not show higher average real living standards.
Answer and reasoning · 答案与解析
In a simple closed model with no tax or imports, MPC = 0.8 gives multiplier k = 1/(1 − 0.8) = 5. An autonomous injection of 10 gives a modelled income rise of 50; taxes and imports add leakages in a fuller model.
- Accurate relevant concept (1)
- Specific evidence from the case (1)
- Connected reasoning (2)
State the model assumptions before using 5 as a prediction. / An AD increase can raise real output or mainly raise prices, depending on spare capacity and supply conditions.
4 · Macroeconomic objectives and policies
monetary policy · supply-side policy
U4-Q1 · 2 marks
Which information matters most when choosing an inflation policy?
Answer and reasoning · 答案与解析
Whether inflation is driven mainly by excess demand or rising costs.
U4-Q2 · 4 marks
Explain the mechanism or reasoning in this original case: A government wants lower inflation and lower unemployment at the same time. Whether these goals conflict depends on why prices and unemployment changed.
Answer and reasoning · 答案与解析
An interest-rate rise may reduce borrowing, spending and aggregate demand, easing demand-pull inflation. If inflation came from imported fuel, the policy may lower output without directly repairing the fuel shortage.
- Accurate relevant concept (1)
- Specific evidence from the case (1)
- Connected reasoning (2)
Do not write that higher rates always reduce inflation immediately. / Compare effectiveness, exchange-rate effects, indebted households, confidence and lags before reaching a conditional judgement.
5 · Firms, costs and market structures
marginal cost · contestability
U5-Q1 · 2 marks
Should the firm add the 101st unit under these figures?
Answer and reasoning · 答案与解析
No: marginal cost exceeds marginal revenue, reducing profit.
U5-Q2 · 4 marks
Explain the mechanism or reasoning in this original case: A firm can sell more only by reducing its price. Extra sales add revenue, but may also reduce revenue on units already sold.
Answer and reasoning · 答案与解析
At Q = 100, total revenue is 1,000 and total cost is 800, giving profit 200. At Q = 101, revenue is 1,006 and cost is 809. The extra unit adds MR = 6 and MC = 9, so profit falls by 3; expansion is not justified by revenue alone.
- Accurate relevant concept (1)
- Specific evidence from the case (1)
- Connected reasoning (2)
Market concentration does not prove collusion. Contestability depends on entry and exit barriers, including sunk costs. / Separate short-run shutdown decisions from long-run exit and distinguish profit from cash flow.
6 · Labour markets and intervention
derived demand · monopsony
U6-Q1 · 2 marks
What is the worker's marginal revenue product in this case?
Answer and reasoning · 答案与解析
96 yuan for the period used in the calculation.
U6-Q2 · 4 marks
Explain the mechanism or reasoning in this original case: A workshop considers hiring another worker who can add output. The hiring decision depends on the revenue that output adds and the worker's cost.
Answer and reasoning · 答案与解析
An extra worker adds 8 units sold at a constant 12 yuan per unit, so MRP = 8 × 12 = 96 yuan. If the relevant wage is 80 yuan, the simplified model supports hiring; other employment costs still matter.
- Accurate relevant concept (1)
- Specific evidence from the case (1)
- Connected reasoning (2)
A minimum wage can have different employment effects under competitive labour markets and monopsony. / Do not apply one diagram to every institution: state bargaining, market structure and enforcement assumptions.
7 · Globalisation, trade and payments
comparative advantage · current account
U7-Q1 · 2 marks
Which country has comparative advantage in radios?
Answer and reasoning · 答案与解析
Country B, because its opportunity cost is one shirt rather than two.
U7-Q2 · 4 marks
Explain the mechanism or reasoning in this original case: Country A needs 2 hours to make a shirt and 4 for a radio. Country B needs 6 for a shirt and 6 for a radio. A is faster at both, but relative costs still differ.
Answer and reasoning · 答案与解析
In A, one radio costs two shirts; in B, one radio costs one shirt. B has comparative advantage in radios. A has comparative advantage in shirts: one shirt costs half a radio in A and one radio in B.
- Accurate relevant concept (1)
- Specific evidence from the case (1)
- Connected reasoning (2)
The model assumes mobility within a country and a simplified production structure. / Exchange-rate changes may not repair a current-account deficit quickly because contracts and elasticities matter.
8 · Development, inequality and the state
development · inequality
U8-Q1 · 2 marks
Which evidence best supports a claim of wider development?
Answer and reasoning · 答案与解析
Improved health and education alongside real income gains, with attention to who benefits.
U8-Q2 · 4 marks
Explain the mechanism or reasoning in this original case: An economy exports more minerals, yet local health and schooling remain poor. Higher output is not sufficient evidence of broad development.
Answer and reasoning · 答案与解析
A rural road can lower transport costs and connect producers to buyers. Health services can improve workers' capabilities. Compare the projects using local bottlenecks, distribution, environmental effects and opportunity cost, rather than GDP alone.
- Accurate relevant concept (1)
- Specific evidence from the case (1)
- Connected reasoning (2)
Aid may support capacity or create dependency; debt relief frees resources only if spending and institutions use them well. / Use several indicators and recognise inequality hidden by national averages.