AQA A-Level Economics: Model Answers for Typical Exam Questions | A-Level AQA 经济：典型例题详解

📚 AQA A-Level Economics: Model Answers for Typical Exam Questions | A-Level AQA 经济：典型例题详解

This article provides model answers for typical AQA A-Level Economics exam questions, covering both microeconomic and macroeconomic topics. Each section presents a question in English and Chinese, followed by a step-by-step explanation that mirrors the standard expected by AQA examiners. Use these as a revision tool to master key concepts, diagrams, calculations, and evaluation skills.

本文提供 A-Level AQA 经济学典型考题的范例详解，涵盖微观与宏观主题。每部分先以英汉双语给出题目，再逐步展示符合 AQA 考官标准的解答过程。考生可将本文作为复习工具，掌握核心概念、图示、计算和评估能力。

1. Demand and the Impact of Substitute Goods | 需求与替代品的影响

Example: Explain how an increase in the price of a substitute good affects the demand for a product. (4 marks)

例题：解释替代品价格的上升如何影响一种产品的需求。（4分）

A substitute good is one that can be used in place of another, for instance, tea and coffee. When the price of a substitute (e.g. coffee) rises, consumers switch their purchases to the relatively cheaper alternative (tea). This increases the demand for tea at every price level. The demand curve shifts to the right from D₁ to D₂, leading to a higher equilibrium price and quantity, ceteris paribus.

替代品是指可以替代另一种商品的物品，例如茶和咖啡。当替代品（如咖啡）的价格上涨时，消费者会转向购买相对便宜的替代品（茶）。这会在每一价格水平上增加茶的需求，需求曲线从 D₁ 右移至 D₂，均衡价格和数量均上升，其他条件不变。

The strength of the effect depends on the closeness of the substitutes. If the two goods are weak substitutes, the demand shift will be small. In an exam, always draw a clear diagram with properly labelled axes and an arrow showing the shift, then state the outcomes for both price and quantity.

这种效应的强弱取决于替代品的接近程度。若两种商品是弱替代品，需求移动就会很小。考试时务必画出清晰的图示，正确标注坐标轴并用箭头标明移动方向，随后阐明价格和数量的变化结果。

2. Supply and Rising Costs of Production | 供给与生产成本的上升

Example: Explain why an increase in the cost of raw materials is likely to reduce the supply of a good. (4 marks)

例题：解释为什么原材料成本上升可能会减少一种商品的供给。（4分）

Raw materials are a key input in production. When their cost rises, firms face higher production costs, which reduces profitability at any given output level. Consequently, producers are willing and able to supply less at each price. The supply curve shifts leftwards from S₁ to S₂, causing the equilibrium price to rise and the equilibrium quantity to fall.

原材料是生产中的关键投入品。其成本上升时，企业面临更高的生产成本，这削弱了任一产出水平上的盈利能力。因此，生产者在各个价位上愿意并能够供给的数量减少，供给曲线从 S₁ 左移至 S₂，导致均衡价格上升、均衡数量下降。

If raw materials account for a large share of total costs, the leftward shift will be more pronounced. In addition, short-run supply often tends to be price inelastic, meaning the price increase may be more dramatic than the quantity adjustment.

如果原材料在总成本中所占比重很大，左移幅度会更显著。此外，短期供给往往缺乏价格弹性，这意味着价格的上涨可能比数量的调整更为剧烈。

3. Calculating Price Elasticity of Demand (PED) | 计算需求价格弹性 (PED)

Example: A firm raises the price of its product from £10 to £12, and quantity demanded falls from 1000 units to 800 units per month. Use the midpoint method to calculate the price elasticity of demand and interpret the result. (4 marks)

例题：某企业将产品价格从 10 英镑提高到 12 英镑，每月需求量从 1000 单位下降到 800 单位。使用中点法计算需求价格弹性，并解释结果。（4分）

Midpoint formula: PED = (%ΔQ) / (%ΔP). Change in quantity (ΔQ) = 800 − 1000 = −200. Average quantity = (1000 + 800)/2 = 900. %ΔQ = (−200 ÷ 900) × 100 = −22.2%. Change in price (ΔP) = 12 − 10 = +2. Average price = (10 + 12)/2 = 11. %ΔP = (2 ÷ 11) × 100 = +18.2%. Thus PED = −22.2% ÷ 18.2% = −1.22. Ignoring the minus sign, the value of 1.22 indicates that demand is price elastic: a 1% rise in price leads to a 1.22% fall in quantity demanded. Since demand is elastic, raising the price will cause total revenue to decrease.

中点公式：PED = (%ΔQ) / (%ΔP)。数量变化 (ΔQ) = 800 − 1000 = −200。平均数量 = (1000 + 800)/2 = 900。%ΔQ = (−200 ÷ 900) × 100 = −22.2%。价格变化 (ΔP) = 12 − 10 = +2。平均价格 = (10 + 12)/2 = 11。%ΔP = (2 ÷ 11) × 100 = +18.2%。因此 PED = −22.2% ÷ 18.2% = −1.22。忽略负号，数值 1.22 表明需求富有价格弹性：价格每上升 1%，需求量下降 1.22%。因为需求富有弹性，提价会导致总收益下降。

Always show your working clearly in the answer booklet and state the interpretation logically: PED > 1 implies elastic demand, which has direct implications for pricing strategy and revenue. This calculation often forms the basis of a longer data-response question.

在答题纸上务必清晰展示计算过程，并有逻辑地给出解释：PED > 1 意味着弹性需求，这直接关系到定价策略和收益。这种计算通常是更复杂的数据响应题的基础。

4. Negative Production Externalities and a Pigouvian Tax | 负生产外部性与庇古税

Example: Using a diagram, explain how a negative production externality leads to market failure, and assess the effectiveness of an indirect tax to correct it. (15 marks)

例题：使用图示说明负生产外部性如何导致市场失灵，并评估征收间接税以纠正该问题的有效性。（15分）

A negative production externality occurs when a firm’s activity imposes costs on third parties not reflected in market prices. The marginal social cost (MSC) lies above the marginal private cost (MPC). In a free market, firms produce where MPC = marginal private benefit (MPB) at output Qm. The socially optimal output, however, is where MSC = MSB at Qs. Overproduction (Qm > Qs) creates a deadweight welfare loss, shown by the triangle between MSC and MSB over the excess units.

负生产外部性出现在企业的活动给第三方带来成本，而市场价格未能反映这些成本时。此时边际社会成本 (MSC) 高于边际私人成本 (MPC)。在自由市场中，企业在 MPC = 边际私人收益 (MPB) 处生产，产量为 Qm；但社会最优产量为 MSC = MSB 对应的 Qs。过度生产 (Qm > Qs) 造成无谓福利损失，即超额单位上 MSC 与 MSB 之间的三角区域。

An indirect tax set equal to the marginal external cost at Qs (a Pigouvian tax) shifts the MPC curve upward to MPC + tax,

Published by TutorHao | A-Level Economics Revision Series | aleveler.com

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