📚 Year 9 Cambridge Economics: Case Study Practical Exercises | Year 9 Cambridge 经济：案例分析实战演练
Case studies are at the heart of Cambridge Economics, bridging theory and real-world decision-making. In Year 9, you begin to sharpen your analytical skills by examining scenarios that mirror everyday economic problems. This practical guide walks you through a step-by-step approach to case study success, complete with a worked example on the mobile phone market. By the end, you will know exactly how to read a case, identify issues, apply concepts, and structure high-scoring answers.
案例分析是剑桥经济学的核心，它将理论与现实决策紧密连接。在九年9，你开始通过研究反映日常经济问题的情景来锻炼分析能力。本实战指南将带你一步步掌握案例分析的成功方法，并配有手机市场的完整示例。学完之后，你将清楚如何阅读案例、识别问题、运用概念，并组织出高分的答案。
1. Understanding the Case Study Approach | 理解案例分析的方法
A case study in economics is not a story to simply retell. It is a puzzle that requires you to apply economic ideas to explain what is happening and to evaluate possible solutions. Examiners want to see you can move from describing events to analysing them using models like demand and supply, opportunity cost, and stakeholder impacts.
经济学中的案例分析不是一个简单复述的故事。它是一个需要你运用经济思想来解释发生了什么并评估解决方案的谜题。考官希望看到你能够从描述事件升级到用供求模型、机会成本和利益相关者影响等工具来分析事件。
Your first job is to read carefully and separate facts from opinions. Highlight numbers, names of groups (consumers, producers, government), and any mention of changes in prices, incomes, technology, or taxes. These are the clues that trigger the relevant economic theory.
你的第一个任务是仔细阅读，分清事实和观点。高亮数字、群体名称（消费者、生产者、政府）以及任何关于价格、收入、技术或税收变化的提及。这些是触发相关经济理论的线索。
2. Essential Economic Concepts to Master | 必须掌握的关键经济概念
Before tackling any case, ensure you have a firm grasp of the foundational concepts most frequently tested in Year 9 Cambridge Economics. The table below lists them; keep it as your mental checklist during the exam.
在处理任何案例之前，确保你牢牢掌握了九年9剑桥经济中最常考的基础概念。下表列出了它们；在考试中把它作为你的心理检查清单。
| English Concept | 中文概念 | Brief Explanation |
|---|---|---|
| Scarcity & Choice | 稀缺性与选择 | Resources are limited, so every choice has an opportunity cost. |
| Opportunity Cost | 机会成本 | The next best alternative foregone when a decision is made. |
| Demand & Supply | 需求与供给 | The relationship between price and quantity from buyers' and sellers' sides. |
| Equilibrium Price | 均衡价格 | The price where quantity demanded equals quantity supplied (Qd = Qs). |
| Price Elasticity of Demand (PED) | 需求的价格弹性 | Responsiveness of Qd to a change in price; formula: PED = %ΔQd / %ΔP. |
| Price Elasticity of Supply (PES) | 供给的价格弹性 | Responsiveness of Qs to a change in price. |
| Externalities | 外部性 | Third-party spillover effects (positive or negative) from production/consumption. |
| Government Intervention | 政府干预 | Taxes, subsidies, regulations, and price controls used to correct market failures. |
You do not need to use every concept in every case. The skill lies in selecting the right tool for the scenario. For example, a case about rising house prices will demand supply and demand analysis; a case about sugar tax will require elasticity and externality thinking.
你不需要在每个案例中都使用所有概念。技巧在于为情景选择合适的工具。例如，关于房价上涨的案例需要用供求分析；关于糖税的案例则需要弹性和外部性的思考。
3. How to Read and Deconstruct a Case Study | 如何阅读与解构案例
Begin by skimming the questions before reading the case text. This tells you what to look for. Then, read the case actively: underline any data (50,000 units, £200), time periods ('recently', 'over the next year'), and key economic changes (technological improvement, rise in income, new tax).
在阅读案例文本之前，先略读问题。这会告诉你需要寻找什么。然后，主动阅读案例：划出任何数据（50,000单位、£200）、时间段（“最近”、“明年”）以及关键经济变化（技术进步、收入增加、新税）。
Use the DIAGRAM method: D – Describe the situation briefly; I – Identify the economic concepts; A – Analyse using the appropriate model (shift demand or supply curves, show new equilibrium); G – Graph if asked (even a rough sketch helps); R – Relate to the stakeholders; A – Answer the question directly; M – Mention any assumptions or limitations.
使用图解分析法：D – 简要描述情况；I – 识别经济概念；A – 运用适当的模型进行分析（移动需求或供给曲线，显示新的均衡）；G – 如有要求就画图（哪怕草图也有帮助）；R – 联系利益相关者；A – 直接回答问题；M – 提及任何假设或局限性。
For Year 9, you will often encounter a market scenario with one or two changes happening at the same time. Your task is to untangle which curve shifts, in which direction, and what happens to equilibrium price and quantity.
对于九年9，你经常会遇到一个市场情景，同时发生一两种变化。你的任务是厘清哪条曲线移动、朝哪个方向，以及均衡价格和数量如何变化。
4. Spotting the Economic Problem | 识别经济问题
The economic problem in a case study is rarely stated outright. You must infer it from symptoms like 'prices have risen sharply', 'there are long queues', 'factories are closing', or 'government is losing revenue'. Each symptom points to a core issue: a shortage, a surplus, a negative externality, or market failure.
案例中的经济问题很少被直接说明。你必须从症状中推断，比如“价格急剧上涨”、“排长队”、“工厂在关闭”或“政府正在损失税收”。每个症状都指向一个核心问题：短缺、过剩、负外部性或市场失灵。
A classic Year 9 prompt: 'The local council is concerned about the number of empty shops on the high street.' The economic problem is a surplus of retail space, likely caused by falling demand (online shopping) or changing tastes. Your answer must frame it in terms of demand and supply, not just as a sad story.
九年9的一个典型提示：“地方议会担心高街上空置店铺的数量。”经济问题是零售空间过剩，很可能是由需求下降（网购）或品味变化引起的。你的回答必须用供求来表述，而不仅仅是讲一个悲伤的故事。
5. Applying Demand and Supply Analysis | 应用需求与供给分析
Almost every case study will require you to shift at least one curve. Memorise the key shift factors. Demand shifts right (increases) if there is a rise in income (normal goods), a rise in the price of a substitute, a fall in the price of a complement, a positive change in tastes, or an increase in population. Demand shifts left if the opposite occurs.
几乎每个案例分析都需要你移动至少一条曲线。记住关键的移动因素。如果收入增加（正常商品）、替代品价格上升、互补品价格下降、品味积极变化或人口增加，需求会向右（增加）移动。如果相反情况发生，需求会向左移动。
Supply shifts right (increases) due to better technology, lower input costs, more firms entering the market, or government subsidies. Supply shifts left when there are higher input costs, natural disasters, stricter regulations, or taxes. When both curves shift, you must analyse the combined effect on price and quantity; often one will be indeterminate without knowing the relative size of the shifts.
供给因技术改进、投入成本降低、更多企业进入市场或政府补贴而向右（增加）移动。当投入成本上升、发生自然灾害、监管更严或征税时，供给会向左移动。当两条曲线都移动时，你必须分析对价格和数量的综合影响；若不知道移动的相对幅度，其中一个结果往往不确定。
For instance, if demand increases and supply also increases, equilibrium quantity will definitely rise, but the change in price is ambiguous – it could rise, fall, or stay the same depending on the magnitudes. Always state this ambiguity when relevant to show higher-order thinking.
例如，如果需求增加供给也增加，均衡数量肯定会上升，但价格的变化是模糊的——它可能上升、下降或保持不变，取决于幅度。在相关时始终陈述这种模糊性，以展示高阶思维。
6. Evaluating Market Equilibrium and Changes | 评估市场均衡及其变化
After shifting curves, identify the new equilibrium price (Pₑ) and quantity (Qₑ). Use clear labelling in your diagrams, even if you only describe them in words. State whether the market moves from a situation of shortage to equilibrium or from surplus to equilibrium, and explain why.
移动曲线后，识别新的均衡价格 (Pₑ) 和数量 (Qₑ)。即使只用文字描述，也要在图表中使用清晰的标注。说明市场是从短缺状态走向均衡，还是从过剩走向均衡，并解释原因。
Consider the speed of adjustment. In many real-world markets, prices are 'sticky' – they do not adjust instantly. You can mention this as a reason why shortages or surpluses might persist in the short run. This adds depth to your analysis.
考虑调整的速度。在现实世界许多市场中，价格是“粘性的”——它们不会立即调整。你可以将此作为短缺或过剩在短期内可能持续的原因加以提及。这为你的分析增添了深度。
Also, think about elasticity of demand and supply in this context. If demand for the product is highly inelastic (steep curve), a supply shock will cause a larger price change and a smaller quantity change. Recognising this can help you explain why some prices are more volatile than others.
此外，还要在此背景下考虑需求与供给的弹性。如果产品需求高度缺乏弹性（陡峭曲线），供给冲击将导致较大的价格变化和较小的数量变化。认识到这一点可以帮助你解释为什么某些价格比其他价格更不稳定。
7. Considering Government Interventions | 考虑政府干预措施
Government action appears in many case studies. The most common interventions are indirect taxes (specific or ad valorem), subsidies, maximum price (price ceiling), and minimum price (price floor). You must explain how the intervention shifts the supply curve or sets a price different from the free-market equilibrium.
政府行为出现在许多案例中。最常见的干预措施是间接税（从量或从价）、补贴、最高限价（价格上限）和最低限价（价格下限）。你必须解释干预如何移动供给曲线，或设定一个与自由市场均衡不同的价格。
For a specific tax, the supply curve shifts vertically upward by the amount of the tax. The new equilibrium price paid by consumers rises, but by less than the full tax if demand is not perfectly inelastic. The price received by producers falls. The difference is the government's tax revenue, and you can identify the consumer and producer burdens.
对于从量税，供给曲线向上垂直移动税额的幅度。消费者支付的新均衡价格上升，但如果需求不是完全无弹性，上升幅度小于全部税额。生产者收到的价格下降。两者之差为政府税收，你可以找出消费者和生产者负担的份额。
Always evaluate the intervention: does it achieve its aims? Are there unintended consequences, such as black markets under price ceilings or surpluses under price floors? This evaluation is what distinguishes a very good answer from an average one.
始终要评估干预措施：它达到了目的吗？是否存在意外后果，比如价格上限下的黑市或价格下限下的过剩？这种评估正是区分优秀答案与普通答案的关键。
8. Structuring Your Answer Effectively | 有效组织你的答案
A well-structured answer follows a logical flow: definition, application, analysis, evaluation. Start by defining the key economic term in the question, even if it feels obvious – this secures easy marks. For example, if the question asks about 'opportunity cost', write: 'Opportunity cost is the value of the next best alternative foregone when a choice is made.'
一个结构良好的答案遵循逻辑流程：定义、应用、分析、评估。首先定义问题中的关键经济术语，即使它看起来很明显——这能确保拿下容易得的分数。例如，如果问题问及“机会成本”，请写道：“机会成本是在做出选择时所放弃的次优替代品的价值。”
Next, apply the concept directly to the case facts. Quote a specific number or name from the text. Then use the appropriate diagram or model to analyse the effects. Finally, evaluate: who gains, who loses, is it efficient, what else could be done, and are there any long-term vs short-term trade-offs?
接下来，将该概念直接应用于案例事实。引用文本中的具体数字或名称。然后使用适当的图表或模型分析影响。最后评估：谁获益、谁受损、是否有效率、还能做什么，以及是否存在长期与短期的权衡？
For a 6-mark question, spend roughly 2 minutes: 1 minute on definition and application, 3 minutes on analysis with diagram, and 2 minutes on evaluation. Practice this timing so it becomes second nature.
对于一道6分题，大约花2分钟：1分钟用于定义和应用，3分钟用于图表分析，2分钟用于评估。练习这个时间安排，让它成为习惯。
9. Practice Case Study: The Market for Mobile Phones | 实战案例：手机市场
Read the following case carefully and then attempt the questions that follow. You may sketch supply and demand diagrams to help your thinking.
仔细阅读以下案例，然后尝试回答后面的问题。你可以画出供求图来辅助思考。
The case: 'In the country of Techland, the smartphone market has been growing rapidly. Over the last three years, average household income has risen by 15%. At the same time, advances in robotics have reduced the cost of manufacturing handsets. The government, concerned about electronic waste, has decided to impose a specific tax of £20 on every new smartphone sold. Market data before the tax showed an equilibrium price of £400 and 2 million units sold per year. A recent study estimated the price elasticity of demand (PED) for smartphones in Techland as -0.6, and the price elasticity of supply (PES) as +1.2.'
案例：“在Techland国，智能手机市场一直在快速增长。过去三年，家庭平均收入上升了15%。同时，机器人技术的进步降低了手机制造的成本。政府关注电子废弃物问题，决定对每台售出的新智能手机征收£20的从量税。税收前的市场数据显示均衡价格为£400，年销量为200万台。最近一项研究估算出Techland智能手机的需求价格弹性为-0.6，供给价格弹性为+1.2。”
Questions:
- 1. Explain how the rise in income and the fall in production costs affect the equilibrium price and quantity of smartphones. Use a supply and demand diagram to support your answer. [6 marks]
- 2. Analyse the impact of the £20 tax on the smartphone market. Clearly state the new price paid by consumers, the price received by producers, and the quantity sold. [6 marks]
- 3. Discuss whether the government's tax is an effective policy to reduce the environmental damage from electronic waste. Consider the PED and PES values in your answer. [6 marks]
问题：
- 1. 解释收入上升和生产成本下降如何影响智能手机的均衡价格和数量。用供求图来支持你的答案。[6分]
- 2. 分析£20从量税对智能手机市场的影响。清楚说明消费者支付的新价格、生产者收到的价格以及销售量。[6分]
- 3. 讨论政府的税收政策是否有效地减少了电子废弃物带来的环境损害。在答案中考虑PED和PES的数值。[6分]
10. Model Answer and Examiner Insights | 参考答案与考官见解
Question 1 Model Answer: Income is a determinant of demand. As household income rises by 15%, demand for smartphones – a normal good – increases, shifting the demand curve to the right from D₀ to D₁. Advances in robotics lower production costs, which increases supply, shifting the supply curve to the right from S₀ to S₁. When both demand and supply increase, the equilibrium quantity definitely rises. The change in equilibrium price is ambiguous: it could rise, fall, or remain the same, depending on the relative size of the shifts. In a typical diagram, if the supply increase is larger, price may fall slightly; if the demand increase is larger, price rises. The question does not provide the magnitudes, so we cannot determine the exact price change.
问题1参考答案：收入是需求的一个决定因素。随着家庭收入上升15%，对智能手机——一种正常商品——的需求增加，需求曲线从D₀向右移动到D₁。机器人技术的进步降低了生产成本，这增加了供给，供给曲线从S₀向右移动到S₁。当需求和供给都增加时，均衡数量肯定上升。均衡价格的变化是模糊的：它可能上升、下降或保持不变，取决于移动的相对幅度。在一个典型的图表中，如果供给增加更大，价格可能小幅下降；如果需求增加更大，价格上升。题目没有提供幅度，因此我们不能确定确切的价格变化。
Examiner insight: Many students forget to mention the ambiguity in price when both curves shift. Stating 'the equilibrium quantity increases unambiguously, but the price effect depends on the magnitude of the shifts' earns full analysis marks. Always label initial and new curves D₀, D₁, S₀, S₁, and show Pₑ, Qₑ before and after.
考官见解：许多学生忘记在两条曲线都移动时提及价格的模糊性。陈述“均衡数量明确增加，但价格效应取决于移动幅度”能拿下全部分析分。始终将初始曲线和新曲线标注为D₀, D₁, S₀, S₁，并显示前后的Pₑ, Qₑ。
Question 2 Model Answer: A specific tax of £20 shifts the supply curve vertically upward by £ elasticity values, we can calculate the tax incidence. The consumer burden = (PES / (PES + |PED|)) × tax = (1.2 / (1.2 + 0.6)) × £20 = (1.2/1.8) × £20 = 0.6667 × £20 = £13.33. The producer burden = (|PED| / (PES + |PED|)) × tax = (0.6/1.8) × £20 = £6.67. Therefore, consumers pay £413.33 and producers receive £400 - £6.67 = £ er the consumer burden; here demand is inelastic (-0.6), so consumers bear a larger share.
问题2参考答案：£20的从量税使供给曲线垂直向上移动£20，从S₀到S₁（或从技术进步后的新供给曲线开始）。利用弹性数值，我们可以计算税收负担。消费者负担 = (PES / (PES + |PED|)) × 税额 = (1.2 / (1.2 + 0.6)) × £20 = (1.2/1.8) × £20 = 0.6667 × £20 = £13.33。生产者负担 = (|PED| / (PES + |PED|)) × 税额 = (0.6/1.8) × £20 = £6.67。因此，消费者支付£413.33，生产者每台收到£400 - £6.67 = £393.33。新均衡数量下降。相对于供给，需求越缺乏弹性，消费者负担越大；这里需求缺乏弹性(-0.6)，因此消费者承担了较大份额。
Examiner insight: Always show the formula and the calculation steps. Even if your final arithmetic is slightly off, the method earns marks. Remember to express the new consumer price as '£400 + consumer burden' and the producer price as '£400 - producer burden' (assuming the original price is the starting point before tax). If you work from the post-technological change equilibrium, you must adjust the base price accordingly. In this case, we used the given equilibrium of £400 for clarity.
考官见解：始终展示公式和计算步骤。即使最终算数稍有偏差，方法也能得分。记住将新的消费者价格表示为“£400 + 消费者负担”，生产者价格为“£400 - 生产者负担”（假设初始价格是税收前的起点）。如果你从技术进步后的均衡出发，必须相应调整基准价格。为清晰起见，这里我们使用了给定的£400均衡。
Question 3 Model Answer: e quantity demanded and therefore waste. However, the effectiveness depends on PED. With PED = -0.6, demand is inelastic; a price increase of £ eover, the inelastic demand suggests consumers view smartphones as essential, so they may simply pay more rather than buy fewer. The tax also raises revenue, which the government could hypothetically use to fund recycling programmes, but this is not guaranteed. On the positive side, the tax internalises some of the external cost, making the market outcome closer to the social optimum. Nevertheless, a tax on new phones might encourage a black market or push consumers to buy cheaper, perhaps more polluting, alternatives. Overall, the tax is a partial solution; it is more effective as a revenue-raiser than as a quantity-reducer in this case, due to low PED. To be truly effective, the government could combine the tax with public awareness campaigns and subsidies for e-waste recycling.
问题3参考答案：政府旨在减少电子废弃物，这是一种负消费外部性。税收提高了手机价格，应该会减少需求量，从而减少废弃物。然而，有效性取决于PED。PED = -0.6，需求缺乏弹性；消费者价格上升£13.33导致需求量百分比的减少相对较小。这意味着该税可能不会显著减少废弃物。此外，缺乏弹性的需求表明消费者将智能手机视为必需品，因此他们可能只会多付钱而不是少买。该税还带来了税收收入，政府理论上可以用这些收入资助回收项目，但这并没有保证。从积极方面看，该税将部分外部成本内部化，使市场结果更接近社会最优。然而，对新手机征税可能催生黑市，或促使消费者购买更便宜、可能污染更严重的替代品。总体而言，该税是一个部分解决方案；在本案例中，由于低PED，它作为增收手段的作用比作为数量减少手段更有效。为了真正有效，政府可以将税收与公众意识宣传和电子废弃物回收补贴结合起来。
Examiner insight: High marks go to answers that evaluate from multiple angles – consumer behaviour, environmental impact, government revenue, and unintended consequences. Use elasticity to gauge effectiveness. Mention 'internalising the externality' as a theoretical advantage. A clear conclusion that does not sit on the fence but acknowledges limitations demonstrates strong evaluation skills.
考官见解：从多个角度进行评估的答案能拿高分——消费者行为、环境影响、政府税收以及意外后果。用弹性来评估有效性。提及“将外部性内部化”作为理论优势。一个不持骑墙态度但承认局限性的明确结论，能展示出强大的评估能力。
Published by TutorHao | Economics Revision Series | aleveler.com
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