📚 A-Level Economics: Typical Example Questions Explained | A-Level 经济：典型例题详解
Mastering A-Level Economics is not just about memorising theories and diagrams; it requires the ability to apply concepts to a wide range of real-world scenarios and typical exam questions. This article walks you through carefully selected worked examples, covering microeconomic and macroeconomic topics, to help you develop a structured approach to analysis, evaluation and precise use of economic vocabulary. Each question is broken down step by step, with the English explanation immediately followed by its Chinese equivalent, ensuring bilingual learners can follow both languages seamlessly.
掌握A-Level经济学不仅仅需要记住理论和图表，更要求能够将概念应用到各种现实场景和典型考题中。本文通过精选的例题详解，涵盖微观与宏观两大领域，帮助你培养有条理的分析与评估能力，并精准使用经济学词汇。每道题都按步骤拆解，英文解释后紧跟对应的中文，确保双语学习者能无缝理解。
1. Price Elasticity of Demand and Total Revenue | 需求价格弹性与总收入
Question: A cinema charges £12 per ticket and sells 800 tickets per week. After reducing the price to £10, ticket sales rise to 1,200 per week. (a) Calculate the price elasticity of demand (PED) using the midpoint formula. (b) Explain what the PED value implies for the cinema's total revenue and discuss whether the price cut was a sound business decision.
例题：一家影院票价定为12英镑，每周售出800张票。票价下调至10英镑后，销量升至每周1200张。(a) 用中点公式计算需求价格弹性。(b) 解释该弹性值对影院总收入意味着什么，并讨论此次降价是否为明智的商业决策。
Answer (a): 0)/2 = 11. So PED = (400 / -2) × (11 / 1000) = -200 × 0.011 = -2.2. Alternatively, using simple percentages with the midpoint approach gives a consistent value of |2.2|, so the coefficient is -2.2.
解答 (a)：中点公式为 PED = (ΔQ / ΔP) × [(P₁+P₂)/2 ÷ (Q₁+Q₂)/2]。此题 ΔQ = +400，ΔP = -2。平均数量 = (800+1200)/2 = 1000；平均价格 = (12+10)/2 = 11。因此 PED = (400 / -2) × (11 / 1000) = -200 × 0.011 = -2.2。弹性系数的绝对值为2.2，所以 PED = -2.2。
Since the absolute value of PED is greater than 1 (|PED| > 1), demand is price elastic. This means the percentage change in quantity demanded (50% increase using midpoint) is larger than the percentage change in price (about -18.2%), so total revenue should increase.
由于 PED 绝对值大于1（|PED| > 1），需求富有弹性。这意味着需求量变化的百分比（中点法约50%）大于价格变化的百分比（约-18.2%），因此总收入应当上升。
Answer (b): Original revenue = £12 × 800 = £9,600. New revenue = £10 × 1,200 = £12,000. The £ on causes a proportionately larger increase in quantity, lifting total revenue. The cinema' o consider capacity constraints and whether the higher volume might affect the viewing experience.
解答 (b)：原收入 = 12 × 800 = 9600英镑。新收入 = 10 × 1200 = 12000英镑。收入增加2400英镑验证了弹性计算。当需求富有弹性时，降价带来需求量更大比例的增加，从而提升总收入。影院的举措在商业上是合理的，前提是新增成本（如人工、保洁）不会超过收入增长。但管理者还必须考虑座位容量限制，以及高上座率是否影响观影体验。
2. Supply Elasticity and the Speed of Adjustment | 供给弹性与调整速度
Question: Explain why the price elasticity of supply (PES) for fresh strawberries is likely to be very low in the immediate run but much higher over a period of one year. Use the concepts of fixed and variable factors of production.
例题：解释为什么新鲜草莓的供给价格弹性（PES）在极短期内可能非常低，但在一年之内会高出许多。请运用固定生产要素和变动生产要素的概念。
arvest is determined by the planting decisions made months earlier. Therefore, even if the market price surges, the quantity supplied cannot respond, making PES perfectly inelastic (PES = 0).
在瞬期或极短期中，所有生产要素都是固定的。农户无法立即让更多草莓成熟；收获量取决于几个月前的种植决策。因此，即便市场价格飙升，供给量也无法作出反应，此时供给弹性完全缺乏弹性（PES = 0）。
Over a one-year period, many factors become variable. Growers can plant more strawberry seedlings, rent additional land, install polytunnels for early ripening, and hire extra labour. The supply curve becomes more elastic. The PES value moves closer to unity or higher, as producers can significantly expand output in response to sustained higher prices. The longer the time horizon, the greater the scope for adjusting variable factors, hence the more elastic the supply.
在一年的时间跨度里，许多要素变为可变的。种植者可以栽种更多草莓苗、租用额外土地、搭建塑料大棚以提早成熟，并雇佣更多劳动力。供给曲线变得更加富有弹性。PES 值趋近于1或更高，因为生产者能够针对持续的高价格大幅扩大产出。时间跨度越长，调整可变要素的空间越大，供给弹性也就越大。
3. Market Equilibrium, Price Controls and Shortages | 市场均衡、价格管制与短缺
Question: hly rent in pounds and Q is the number of apartments. (a) Find the equilibrium rent and quantity. (b) The government imposes a rent ceiling of £80. Calculate the resulting shortage and discuss potential consequences.
例题：某城市租赁公寓的需求和供给分别为 Qd = 5000 - 20P 和 Qs = -1000 + 30P，其中 P 为月租金（英镑），Q 为公寓数量。(a) 求均衡租金和数量。(b) 若政府实行租金上限80英镑，计算由此产生的短缺，并讨论可能的后果。
Answer (a): Set Qd = Qs: 5000 - 20P = -1000 + 30P → 5000 + 1000 = 30P + 20P → 6000 = 50P → P = £120. Substitute into Qd: Q = 5000 - 20(120) = 2600 apartments. Equilibrium rent is £120, quantity is 2,600.
解答 (a)：令 Qd = Qs：5000 - 20P = -1000 + 30P → 5000 + 1000 = 30P + 20P → 6000 = 50P → P = 120英镑。代入 Qd：Q = 5000 - 20(120) = 2600 套。均衡租金为120英镑，数量为2600套。
Answer (b): At the rent ceiling of £ creates excess demand. Landlords may reduce maintenance, take apartments off the rental market, or demand side-payments, leading to a deterioration of housing quality. Some tenants might secure flats at the controlled price but face longer search times, while others are forced into the unregulated subletting market. Black markets can emerge, undermining the policy goal of affordable housing for all.
解答 (b)：在租金上限80英镑下，Qd = 5000 - 20(80) = 3400；Qs = -1000 + 30(80) = 1400。短缺 = 3400 - 1400 = 2000 套。价格上限导致超额需求。房东可能减少维修保养、将公寓退出租赁市场或索要额外费用，致使住房质量恶化。部分租户可能以受控价格租到房屋，但找寻时间延长，其他人则被迫进入不受监管的转租市场。黑市可能滋生，从而破坏政策初衷——让所有人享有可负担住房。
4. Tax Incidence and the Role of Elasticity | 税收归宿与弹性的作用
Question: The government introduces a specific tax of £5 per pack on cigarettes. The demand for cigarettes is highly inelastic, while supply is relatively elastic. With the aid of a simple numerical illustration, explain how the tax burden is distributed between consumers and producers.
例题：政府对每包香烟征收5英镑的从量税。香烟需求高度缺乏弹性，而供给相对富有弹性。请用一个简单的数值例子，解释税负如何在消费者和生产者之间分配。
Before the tax, assume equilibrium occurs at P = £10 and Q = 200 million packs. The tax shifts the supply curve vertically upward by £ re less responsive to price changes. The new consumer price Pc rises significantly, say to £14, while the producer receives only Ps = Pc - tax = £9. Thus, out of the £5 tax, consumers bear £4 (80%) and producers bear £1 (20%).
征税前，假设均衡价格为10英镑，数量为2亿包。税收使供给曲线垂直上移5英镑，形成新供给曲线 S + tax。需求缺乏弹性意味着消费者对价格变化不敏感。新的消费者支付价格 Pc 大幅升至14英镑，而生产者实际得到 Ps = Pc - tax = 9英镑。因此，在5英镑的税负中，消费者承担了4英镑（80%），生产者承担1英镑（20%）。
This distribution occurs because the more inelastic side of the market bears a larger share of the tax. Cigarette smokers have few close substitutes and a strong habit, so quantity demanded does not fall sharply when prices rise. Producers, however, can switch resources relatively easily, so their supply is elastic. The policy therefore both raises government revenue and discourages smoking by raising the consumer price, but its regressive nature may affect lower-income groups disproportionately.
之所以如此分配，是因为市场中弹性更小的一方承担更大比例的税负。吸烟者少有近似替代品且习惯性强，因此价格上升时需求量下降不大。而生产者能较容易地转移资源，供给富有弹性。因此这政策既能增加财政收入，又能通过提高消费价格抑制吸烟，但其累退性质可能对低收入群体造成过大影响。
5. Negative Externalities and Pigouvian Tax | 负外部性与庇古税
Question: cost (MPC) is given by MPC = 20 + 2Q, and the marginal external cost (MEC) is constant at £ te the Pigouvian tax needed to internalise the externality and explain its welfare effect.
例题：一家化工厂向河中排放废物，对下游渔业造成外部成本。边际私人成本（MPC）为 MPC = 20 + 2Q，边际外部成本（MEC）恒为每单位8英镑。边际社会收益（MSB）为 MSB = 80 - Q。(a) 求自由市场产量和社会有效产量。(b) 计算所需的庇古税以内部化外部性，并解释其福利效应。
Answer (a): PC + MEC = 28 + 2Q. Set MSC = MSB: 28 + 2Q = 80 - Q → 3Q = 52 → Q ≈ 17.33 units. Overproduction in the free market by about 2.67 units creates a deadweight loss.
解答 (a)：自由市场均衡：MPC = MSB → 20 + 2Q = 80 - Q → 3Q = 60 → Q = 20 单位。工厂忽略了外部成本。社会有效产量需考虑 MSC = MPC + MEC = 28 + 2Q。令 MSC = MSB：28 + 2Q = 80 - Q → 3Q = 52 → Q ≈ 17.33 单位。自由市场的过度生产约为2.67单位，造成了无谓损失。
Answer (b): A Pigouvian tax equal to the MEC (£8 per unit) should be set. With the tax, the firm's effective MPC shifts upward to 28 + 2Q, exactly aligning with MSC. The new profit-maximising output becomes the socially efficient level of 17.33 units. The tax revenue (approx. £138.64) can be used to compensate affected parties or reduce other distortive taxes. The deadweight loss is eliminated, and social welfare is maximised.
解答 (b)：应设定等于 MEC（每单位8英镑）的庇古税。征税后，企业实际的边际成本曲线上移至 28 + 2Q，与 MSC 完全一致。新的利润最大化产量变为社会有效水平17.33单位。税收收入（约138.64英镑）可用于补偿受损害的群体或减轻其他扭曲性税收。无谓损失被消除，社会福利达到最大化。
6. Market Failure: Public Goods and the Free-Rider Problem | 市场失灵：公共物品与搭便车问题
Question: Street lighting is often provided by local governments rather than private firms. Using the concepts of non-excludability and non-rivalry, explain why street lighting is a public good and why the free market will fail to supply the socially optimal quantity.
例题：街道路灯通常由地方政府而非私人企业提供。运用非排他性和非竞争性的概念，解释为什么路灯是公共物品，以及为什么自由市场无法提供社会最优数量。
Street lighting is non-excludable: once installed, it is impossible to prevent anyone from benefiting from the light, whether they pay or not. It is also non-rivalrous: one person's use of the light does not reduce the brightness available to others. Because of non-excludability, a private firm cannot force all beneficiaries to pay, leading to the free-rider problem — individuals will understate their true willingness to pay, hoping others will cover the cost.
路灯具有非排他性：一旦安装，便无法阻止任何人从中获益，无论其是否付费。它还具有非竞争性：一个人使用灯光并不减少他人可获得的亮度。由于非排他性，私人企业无法强制所有受益者付费，从而导致搭便车问题——个人会低估自己的真实支付意愿，指望他人承担成本。
In a free market, the private marginal benefit curve lies below the social marginal benefit, because free riders are not counted. The resulting equilibrium quantity is below the socially efficient level, potentially zero. Government intervention through compulsory taxation and public provision can overcome this failure by ensuring output closer to the level where marginal social benefit equals marginal social cost.
在自由市场中，私人边际收益曲线低于社会边际收益，因为搭便车者未被计入。由此产生的均衡供给量会低于社会有效水平，甚至可能为零。政府通过强制征税并直接提供公共物品，可以化解这种市场失灵，确保产出接近社会边际收益等于社会边际成本的水平。
7. Measuring Unemployment and Types of Joblessness | 衡量失业与失业类型
Question: In a hypothetical economy, the working-age population is 40 million. The labour force participation rate is 62.5%, and 23 million people are employed. (a) Calculate the number of unemployed and the unemployment rate. (b) Distinguish between frictional, structural, and cyclical unemployment, giving one example of each.
例题： Published by TutorHao | A-Level Economics Revision Series | aleveler.com
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