📚 Case Study Practical Exercises | 案例分析实战演练
Case studies are a vital part of your WJEC Year 10 Economics exam. They test your ability to apply economic theory to real-world situations, analyse data, and make reasoned evaluations. This article walks you through a complete case study on the sugar tax, giving you a step-by-step approach to master case study questions and build confidence for your assessments.
案例研究是 WJEC 十年级经济考试的重要组成部分。它考查你将经济理论应用于现实情境、分析数据并做出合理论证的能力。本文将通过一个完整的糖税案例研究，带你一步步掌握案例分析题的解题方法，帮助你在考试中建立信心。
1. Understanding the Case Context | 理解案例背景
Let’s begin with a realistic case. The government is concerned about rising obesity levels, particularly among young people. It proposes a specific tax of £0.24 per litre on all sugar-sweetened beverages. The current market for fizzy drinks shows an equilibrium price of £1.20 per litre and an equilibrium quantity of 800 million litres per year.
我们先看一个真实的案例。政府担心肥胖率上升，尤其是年轻人群体。它提议对所有含糖饮料征收每升 £0.24 的特定税。目前汽水市场的均衡价格为每升 £1.20，均衡数量为每年 8 亿升。
Use the following market data to guide your analysis. Demand for sugary drinks is relatively inelastic (PED = –0.4), while supply is more elastic (PES = 1.2). Additionally, consumption of these drinks generates negative externalities, such as increased NHS costs estimated at £0.15 per litre.
使用以下市场数据来指导你的分析：含糖饮料的需求相对缺乏弹性（PED = –0.4），而供给较富有弹性（PES = 1.2）。此外，消费这些饮料会产生负外部性，比如每升增加 NHS 成本约 £0.15。
| Variable | Value |
|---|---|
| Initial price (P₀) | £1.20 per litre |
| Initial quantity (Q₀) | 800 million litres |
| Tax per litre | £0.24 |
| Price elasticity of demand (PED) | –0.4 |
| Price elasticity of supply (PES) | 1.2 |
2. Identifying Key Stakeholders | 识别关键利益相关者
Before starting the diagram, list the groups affected by the tax. Consumers will face higher prices and may reduce consumption. Producers (soft drink manufacturers) could see lower sales and might pass on some of the tax. The government gains tax revenue and hopes to improve public health. The NHS and taxpayers benefit if obesity-related costs fall. Finally, workers in the soft drink industry could be affected if output drops significantly.
在画图之前，先列出受税收影响的群体。消费者将面临更高价格，可能减少消费。生产者（软饮料制造商）可能面临销量下降，并可能将部分税收转嫁出去。政府获得税收收入，并希望改善公共健康。如果与肥胖相关的支出减少，NHS 和纳税人将从中受益。最后，如果产出大幅下降，软饮料行业的工人也可能受到影响。
3. Using Demand and Supply Diagrams | 运用供需图表
Draw a standard demand and supply diagram. Label the initial equilibrium at P₁ = £1.20 and Q₁ = 800m. The tax shifts the supply curve vertically upwards by exactly £0.24, because the tax is a specific amount per unit. The new supply curve is S + tax.
画一个标准的供需图。标出初始均衡点 P₁ = £1.20，Q₁ = 8 亿。由于是每单位定额税，供给曲线垂直上移 £0.24。新的供给曲线为 S + tax。
The new equilibrium occurs at a higher price for consumers (Pc) and a lower quantity (Q₂). The price received by producers (Pp) is Pc minus the tax. Because demand is inelastic, the quantity demanded falls by a relatively small percentage.
新的均衡点对应更高的消费者价格（Pc）和更低的产量（Q₂）。生产者得到的价格（Pp）是 Pc 减去税额。由于需求缺乏弹性，需求量下降的百分比相对较小。
Pc ≈ £1.38, Pp ≈ £1.14, Q₂ ≈ 760 million litres
The diagram confirms that the tax reduces the quantity of sugary drinks consumed, which is the government’s health objective.
图表证实，税收减少了含糖饮料的消费量，这符合政府的健康目标。
4. Analysing Price Elasticity of Demand | 分析需求价格弹性
With a PED of –0.4, demand is price inelastic. This means the percentage change in quantity demanded is smaller than the percentage change in price. As a result, the tax is more effective at raising revenue than at cutting consumption. The total expenditure by consumers will increase because the price rise outweighs the fall in quantity.
由于 PED = –0.4，需求缺乏价格弹性。这意味着需求量变动的百分比小于价格变动的百分比。因此，该税在增加财政收入方面比减少消费量更有效。消费者的总支出将会增加，因为价格上涨幅度超过了数量下降幅度。
If demand were more elastic (e.g. PED = –1.5), the same tax would cause a much larger drop in quantity, greatly reducing externality problems but generating less tax revenue for the government.
如果需求更富弹性（如 PED = –1.5），同样的税收将导致消费量更大幅度下降，从而大大缓解外部性问题，但给政府带来的税收收入会减少。
5. Incidence of the Tax: Who Pays? | 税收归宿：谁承担？
The burden of the tax is shared between consumers and producers depending on the relative elasticities. The formula for the consumer share is PES ÷ (|PED| + PES). Using our numbers: 1.2 ÷ (0.4 + 1.2) = 1.2 ÷ 1.6 = 0.75. This shows consumers bear 75% of the tax.
税收负担由消费者和生产者共同承担，分担比例取决于相对弹性。消费者负担份额的公式为：PES ÷ (|PED| + PES)。代入数值：1.2 ÷（0.4 + 1.2）= 0.75。这说明消费者承担了税负的 75%。
In money terms, the consumer pays £0.18 of the £0.24 tax per litre, while producers bear £0.06. The price kept by producers falls from £1.20 to £1.14, reducing their incentive to supply. This is why some small producers might leave the market.
以货币计算，每升 £0.24 的税收中，消费者支付 £0.18，生产者承担 £0.06。生产者保留的价格从 £1.20 降至 £1.14，这削弱了供给激励。这就是部分小型生产商可能退出市场的原因。
Consumer burden = £0.18, Producer burden = £0.06 per litre
6. Externalities and Market Failure | 外部性与市场失灵
Sugary drinks create negative externalities in consumption. A consumer buying a can of cola only considers their private benefit and cost, ignoring the additional healthcare costs imposed on society. This leads to overconsumption: the free market quantity is greater than the socially optimum quantity.
含糖饮料在消费中产生负外部性。消费者购买一罐可乐时只考虑个人收益和成本，而忽视强加给社会的额外医疗成本。这导致了过度消费：自由市场数量大于社会最优数量。
The £0.24 tax aims to internalise the externality. Ideally, a tax should equal the marginal external cost at the socially efficient output. Here the external cost is estimated at £0.15 per litre, so the £0.24 tax actually over-corrects slightly. This may be justified on health grounds, but it creates a deadweight loss.
£0.24 的税收旨在将外部性内部化。理想情况下，税额应等于社会有效产出水平下的边际外部成本。此处外部成本估计为每升 £0.15，因此 £0.24 的税收实际上略有过度纠正。这可能出于健康理由而获得支持，但也会造成无谓损失。
7. Government Objectives and Effectiveness | 政府目标与有效性
The government has multiple objectives: reducing obesity, raising revenue, and lowering long-term NHS spending. The inelastic demand means the tax is an excellent revenue raiser, but only moderately successful in cutting consumption (quantity falls by only 5% in our example).
政府有多个目标：减少肥胖、增加收入、降低长期 NHS 支出。需求缺乏弹性意味着该税可以很好地增加收入，但在减少消费方面效果一般（在我们的例子中消费量仅下降 5%）。
Evidence from countries that introduced similar taxes shows that a portion of consumers switch to diet drinks or bottled water. However, low-income households spend a larger share of their income on sugary drinks, so the tax is regressive. This raises an equity concern: is it fair to tax a product that takes a bigger proportion of poor households’ budgets?
引入类似税的国家的经验表明，一部分消费者会转向无糖饮料或瓶装水。然而，低收入家庭在含糖饮料上的支出占其收入的比重更大，因此该税具有累退性。这就引出了一个公平性问题：对在贫困家庭预算中占比较大比例的产品征税是否公平？
8. Evaluating Alternative Policies | 评价替代政策
Instead of a tax, the government could use a minimum price per litre, ban advertising aimed at children, or subsidise healthy alternatives like fruit-infused water. A subsidy on healthy drinks would shift the demand curve for those products rightwards, potentially reducing demand for sugary drinks through the substitution effect.
除了税收，政府还可以设定每升最低价格，禁止针对儿童的广告，或对健康替代品（如果味水）提供补贴。对健康饮品的补贴会使这些产品的需求曲线右移，并可能通过替代效应减少对含糖饮料的需求。
A tax might be easier to implement and provides immediate revenue, but it does not directly educate consumers about healthy choices. Information campaigns could address the root cause — lack of awareness — but take longer to work. The best approach is often a combination of policies.
征税可能更易实施并能立即获得收入，但它并不能直接教育消费者做出健康的选择。宣传活动可以解决根本原因——缺乏认知——但见效较慢。最好的方法通常是政策组合。
9. Drawing Conclusions | 得出结论
In your exam, a strong conclusion weighs up the evidence and makes a supported judgement. For the sugar tax, I would conclude that it is partially effective: it reduces consumption slightly, raises significant revenue, and signals the government’s commitment to public health. However, its regressive nature and limited impact on deeply rooted consumption habits mean it cannot be the only solution.
在考试中，有力的结论需要权衡证据并做出有依据的判断。对于糖税，我会得出结论：它在一定程度上是有效的：它略微减少了消费，带来了可观的收入，并表明了政府对公共健康的承诺。然而，它具有累退性，并且对根深蒂固的消费习惯影响有限，这意味着它不能是唯一的解决方案。
Longer term, a package including taxation, subsidies for healthy foods, and education would be more sustainable and equitable. Always link your conclusion back to the specific case context rather than making general statements.
从长远来看，一个包括征税、健康食品补贴和教育在内的政策组合将更具可持续性也更公平。始终要让你的结论回到具体的案例背景上，而不是泛泛而谈。
10. Practice Exercise: Try It Yourself | 自己试试：配套练习
Now apply the same logical steps to a fresh case. The government is considering a maximum rent control on privately rented flats in a major city, setting a ceiling of £800 per month. The current market rent is £950 per month, and 120,000 flats are rented. The supply of rental housing is price inelastic (PES = 0.6), and demand is price elastic (PED = –1.2).
现在用相同的逻辑步骤分析一个新案例。政府正在考虑对某大城市的私人出租公寓实行最高租金管制，设定租金上限为每月 £800。当前市场租金为每月 £950，出租公寓数量为 12 万套。出租住房的供给价格弹性为缺乏弹性（PES = 0.6），需求价格弹性为富有弹性（PED = –1.2）。
Follow these steps: (1) Draw a diagram showing the initial equilibrium and the price ceiling. (2) Explain whether the ceiling is binding and calculate the likely shortage. (3) Identify the winners and losers — tenants who find a flat, tenants who cannot find one, landlords, and the government. (4) Evaluate the policy using concepts of informal markets, waiting lists, and the effect on quality. (5) Write a two-paragraph conclusion suggesting an alternative or complementary policy.
请遵循以下步骤：（1）画出显示初始均衡和价格上限的图表。（2）解释该上限是否具有约束力，并估算可能出现的短缺。（3）识别赢家和输家——找到房子的租户、找不到房子的租户、房东以及政府。（4）运用黑市、排队名单及对房屋质量影响等概念来评价该政策。（5）写一个两段式的结论，并提出替代性政策或配套政策。
This structured drill will sharpen your evaluation skills and help you tackle any WJEC case study with confidence.
这种结构化的演练将磨炼你的评价能力，帮助你自信地应对任何 WJEC 案例研究。
Published by TutorHao | Economics Revision Series | aleveler.com
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