📚 Case Study Practice for OCR Economics | OCR 经济学案例分析实战演练
Case studies are a vital part of OCR GCSE Economics, testing your ability to apply theoretical concepts to real-world scenarios. This article takes you through a detailed practice case on the global coffee market, covering demand and supply, elasticity, taxation, subsidies, externalities and government intervention. By working step by step, you will sharpen the analytical and evaluative skills needed to achieve a top grade.
案例分析是 OCR 经济学考试的重要组成部分，考察你将理论知识应用于现实场景的能力。本文以全球咖啡市场为详细练习案例，涵盖供求关系、弹性、税收、补贴、外部性与政府干预等主题。通过逐步演练，你将提升获得高分所必需的分析与评价能力。
1. Understanding Case Studies in OCR Economics | 理解 OCR 经济学中的案例分析
In the OCR exam, a case study typically provides data and a short narrative about an economic issue. Your job is to select the right economic concepts, extract relevant information from tables or graphs, and then analyse the problem. You must also evaluate policies, considering their pros and cons and short- and long-run effects. Practice with diverse contexts helps you answer data-response questions confidently under time pressure.
在 OCR 考试中，案例分析通常会提供数据和关于某个经济问题的简短描述。你的任务是选择合适的经学概念，从表格或图表中提取相关信息，然后分析问题。你还必须评价政策，考虑其利弊及短期与长期影响。通过在不同背景下的练习，你能在时间压力下自信地回答数据分析题。
Always start by reading the scenario carefully and highlighting key figures. Identify the main market (product, labour, financial) and note any changes in determinants of demand or supply before drawing diagrams. This structured approach is the foundation of case-study success.
始终要仔细阅读情景并标出关键数字。确定主要市场（产品、劳动力、金融市场），并注意需求和供给决定因素的任何变化，然后再画出图表。这种结构化的方法是案例分析成功的基础。
2. The Case: Coffee Market Dynamics | 案例：咖啡市场动态
Imagine a global market for Arabica coffee beans. Initially, the equilibrium price is $3.00 per kg and the equilibrium quantity is 100 million 60 kg bags per year. A rise in health awareness leads consumers to prefer coffee over sugary drinks, increasing demand. At the same time, unusual frosts in Brazil destroy a significant portion of the harvest, reducing supply.
假设一个全球阿拉比卡咖啡豆市场。初始均衡价格为每公斤 3.00 美元，均衡数量为每年 1 亿袋（每袋 60 公斤）。健康意识的提升使消费者更喜欢咖啡而非含糖饮料，因而增加了需求。同时，巴西异常霜冻摧毁了大部分收成，减少了供给。
The new demand curve shifts to the right: at every price, 20 million more bags are demanded. The supply curve shifts to the left: at every price, 15 million fewer bags are supplied. Use this information to investigate the new equilibrium and market adjustments.
新的需求曲线向右移动：在每个价格上，需求量增加 2000 万袋。供给曲线向左移动：在每个价格上，供给量减少 1500 万袋。利用这一信息研究新的均衡和市场调整。
3. Analysing Demand and Supply Shifts | 分析需求与供给的变动
nd where Qd = Qs, giving P = 3 and Q = 100. With the demand increase of 20 at all prices, new Qd = 270 - 50P. With the supply decrease of 15, new Qs = -65 + 50P.
我们可以用简单的线性假设来模拟市场。假设初始需求：Qd = 250 - 50P；初始供给：Qs = -50 + 50P。均衡由 Qd = Qs 求得，得出 P = 3，Q = 100。需求在每种价格上均增加20，新的需求：Qd = 270 - 50P。供给减少15，新的供给：Qs = -65 + 50P。
ubstituting back: Q = 270 - 50(3.35) = 270 - 167.5 = 102.5. The equilibrium price rises to $ change is modest because both curves shifted in opposite directions relative to quantity.
令新 Qd = 新 Qs：270 - 50P = -65 + 50P → 335 = 100P → P = 3.35。代回得 Q = 270 - 50(3.35) = 270 - 167.5 = 102.5。均衡价格上升至每公斤 3.35 美元，数量小幅上升至 1.025 亿袋。注意价格上升显著而数量变化不大，因为两条曲线相对于数量的移动方向相反。
In exam answers, draw a supply-demand diagram labelling the initial and new curves, showing the price increase and the ambiguous quantity effect. Explain that the demand shift alone would raise both P and Q, but the supply shift pushes P up and Q down, resulting in a smaller net quantity change.
在考试作答时，画出一个供求图，标明初始曲线和新曲线，展示价格上升和数量变化的不确定效果。解释需求变动单独会导致 P 和 Q 均上升，但供给变动会推高价格拉低数量，最终净数量变化较小。
4. Calculating Price Elasticity of Demand | 计算需求价格弹性
Observe a local coffee shop chain. When the price of a regular latte rises from $3.00 to $3.60, the daily quantity demanded falls from 500 cups to 400 cups. Let's calculate the price elasticity of demand (PED).
观察一家本地咖啡连锁店。当普通拿铁的价格从 3.00 美元升至 3.60 美元时，日需求量从 500 杯降至 400 杯。我们来计算需求价格弹性（PED）。
PED = (%ΔQd) ÷ (%ΔP)
PED = ( %ΔQd ) ÷ ( %ΔP )
First, %ΔQd = (400 - 500)/500 × 100 = -20%. %ΔP = (3.60 - 3.00)/3.00 × 100 = 20%. Therefore, PED = -20% ÷ 20% = -1.0. The absolute value is 1, meaning demand is unit elastic at this point.
首先，%ΔQd = (400 - 500)/500 × 100 = -20%。%ΔP = (3.60 - 3.00)/3.00 × 100 = 20%。因此，PED = -20% ÷ 20% = -1.0。绝对值是 1，意味着此时需求具有单位弹性。
ange in quantity demanded, so total revenue remains unchanged. If the original revenue was $3 × 500 = $1500, the new revenue is $3.60 × 400 = $ exact midpoint. More precise calculations confirm constant revenue when PED is exactly -1.
当 PED = -1 时，价格的变动会导致需求量同比例变动，因此总收益不变。如果原始收益为 3 × 500 = 1500 美元，新收益为 3.60 × 400 = 1440 美元，由于取整而略有降低。更精确的计算确认当 PED 恰好为 -1 时收益不变。
In a case study, you might be asked to interpret PED values. If |PED| < 1, the good is inelastic and total revenue moves with price. If |PED| > 1, it is elastic and revenue moves opposite to price. This concept is crucial when analysing tax incidence or pricing strategies.
在案例分析中，你可能需要解释 PED 值。如果 |PED| < 1，商品缺乏弹性，总收益与价格同向变动。如果 |PED| > 1，商品富有弹性，收益与价格反向变动。在分析税收归宿或定价策略时，这一概念至关重要。
5. Impact of a Specific Tax | 从量税的影响
The government decides to impose a specific tax of $ consumption. With the initial supply (S) and demand (D) from our earlier equilibrium (P = $ hifts the supply curve vertically upwards by the tax amount, effectively becoming S + tax.
政府决定对咖啡供应商征收每公斤 0.50 美元的从量税，以增加财政收入并抑制咖啡因消费。基于之前均衡（P = 3.00 美元，Q = 1 亿）的初始供给（S）和需求（D），税收将使供给曲线垂直向上移动税额幅度，实际上变为 S + tax。
new supply: Qs = -20 + 40(P - 0.5) because suppliers receive P - 0.5. So Qs = -20 + 40P - 20 = -40 + 40P. Set equal to demand: 220 - 40P = -40 + 40P → 260 = 80P → P = 3.25. Buyers pay $3.25, sellers receive $3.25 - $0.50 = $2.75. Quantity falls to Q = 220 - 40(3.25) = 90 million bags.
使用更实际的曲线，设需求：Qd = 220 - 40P；供给：Qs = -20 + 40P。无税均衡：220 - 40P = -20 + 40P → P = 3，Q = 100。征税后，新供给: Qs = -20 + 40(P - 0.5) 因为供应商只得到 P - 0.5。故 Qs = -20 + 40P - 20 = -40 + 40P。令其等于需求：220 - 40P = -40 + 40P → 260 = 80P → P = 3.25。买方支付 3.25 美元，卖方获得 3.25 - 0.50 = 2.75 美元。数量降至 Q = 220 - 40(3.25) = 9000 万袋。
Tax incidence: consumers bear $0.25 of the tax per unit, producers bear $0.25. Total tax revenue = tax × new quantity = $0.50 × 90 million = $45 million. The deadweight loss (welfare loss) arises from the reduced trades—the 10 million bags that were previously mutually beneficial are no longer produced.
税收归宿：消费者每单位承担 0.25 美元，生产者承担 0.25 美元。总税收收入 = 税额 × 新数量 = 0.50 × 9000 万 = 4500 万美元。无谓损失（福利损失）源于交易减少——原先互利的 1000 万袋不再生产。
The exact split depends on relative elasticities. Here, demand and supply have identical price sensitivities, so the burden is shared equally. If demand were more inelastic, consumers would pay a larger share.
具体的分担比例取决于相对弹性。这里，需求和供给的价格敏感度相同，因此负担平均分配。若需求更缺乏弹性，消费者将承担更大份额。
6. Subsidies for Sustainable Production | 对可持续生产的补贴
encourage environmentally friendly coffee farming, the government introduces a subsidy of $ per kg paid to farmers who adopt organic practices. Assume initially the market is at P = $3.00, Q = 100 million. The subsidy effectively lowers farmers' costs, shifting the supply curve downwards by the subsidy amount for eligible producers.
为鼓励环保型咖啡种植，政府向采用有机种植方式的农民提供每公斤 0.30 美元的补贴。假设最初市场在 P = 3.00 美元，Q = 1 亿。补贴实际上降低了农民的成本，使符合条件生产者的供给曲线向下移动补贴金额。
changed: Qd = 220 - 40P. Equating: 220 - 40P = -8 + 40P → 228 = 80P → P = 2.85. Buyers pay $2.85, sellers receive $2.85 + $0.30 = $3.15. Quantity rises to Q = 220 - 40(2.85) = 106 million bags.
使用供给：Qs = -20 + 40P。有了补贴，供应商获得 P + 0.30，故 Qs = -20 + 40(P + 0.30) = -20 + 40P + 12 = -8 + 40P。需求不变：Qd = 220 - 40P。等式：220 - 40P = -8 + 40P → 228 = 80P → P = 2.85。买方支付 2.85 美元，卖方获得 2.85 + 0.30 = 3.15 美元。数量上升至 Q = 220 - 40(2.85) = 1.06 亿袋。
The government expenditure on the subsidy is $0.30 × 106 million = $ ty cost. Moreover, it may encourage inefficiency if farmers rely on subsidies rather than improving productivity.
政府补贴总支出为 0.30 × 1.06 亿 = 3180 万美元。尽管消费者享受了更低价格和更多数量，补贴必须由一般税收资助，产生机会成本。此外，如果农民依赖补贴而非提高生产率，可能会鼓励低效率。
In evaluation, consider whether the environmental benefits justify the cost. A cost-benefit analysis might quantify reduced soil erosion and biodiversity gains against fiscal costs and any distortion to global trade.
在评价中，要考虑环境效益是否值得付出该成本。成本效益分析可能会量化减少的土壤流失和生物多样性的增益，并与财政成本和全球贸易的任何扭曲进行权衡。
7. Externalities and Market Failure | 外部性与市场失灵
Coffee production and transportation generate negative externalities. For example, fertiliser runoff contaminates water sources, and shipping coffee across oceans emits CO₂. These costs are not reflected in the market price, leading to over-production and over-consumption from society's viewpoint.
咖啡生产和运输会产生负外部性。例如，肥料径流污染水源，跨洋运输排放二氧化碳。这些成本未反映在市场价格中，从社会的角度看导致过度生产与过度消费。
rginal private cost (MPC) be the supply curve, and suppose marginal external cost (MEC) is $ ilibrium ignores the external cost, so the true socially optimal quantity is lower and the price should be higher to include the full cost.
假设边际私人成本（MPC）为供给曲线，并设边际外部成本（MEC）为每公斤 0.40 美元。边际社会成本（MSC）= MPC + MEC。自由市场均衡忽视外部成本，因此真正社会最优数量更低，价格应更高以反映全部成本。
Conversely, organic coffee farming can create positive externalities, such as enhanced biodiversity and carbon sequestration. The marginal social benefit (MSB) exceeds the marginal private benefit (MPB), causing under-production from society's view. Without intervention, the market fails to achieve allocative efficiency.
相反，有机咖啡种植可产生正外部性，如增加生物多样性和碳固存。边际社会收益（MSB）超过边际私人收益（MPB），从社会角度看导致生产不足。若无干预，市场无法实现配置效率。
Examiners expect you to use diagrams showing MSC > MPC for negative externalities and MSB > MPB for positive externalities, highlighting the welfare loss triangles. To address the market failure, governments can use taxes equal to MEC (Pigouvian taxes) or subsidies equal to external benefit, alongside regulation like emission limits.
考官期望你用示意图展示负外部性时 MSC > MPC 和正外部性时 MSB > MPB，标出福利损失三角。为解决市场失灵，政府可以使用等于 MEC 的税收（庇古税）或等于外部收益的补贴，以及排放限制等监管手段。
8. Government Intervention Evaluation | 政府干预的评价
While taxes and subsidies can correct market failure, they are not perfect. Taxes on coffee might be regressive, taking a larger share of income from low-income households. Moreover, administration costs and tax evasion can reduce effectiveness. A subsidy for organic farming may simply displace conventional farming rather than expanding total green output.
虽然税收和补贴可以纠正市场失灵，但也并非完美。对咖啡征税可能是累退的，将更大比例的收入从低收入家庭处拿走。此外，行政成本和逃税会降低效果。有机农业补贴可能仅仅替代了常规农业，而非扩大绿色总产出。
Global coffee markets are interconnected; a domestic tax may incentivise imports from countries with weaker environmental standards, leading to carbon leakage. This calls for international coordination. Evaluation in your exam must weigh the pros and cons, and you should demonstrate awareness of unintended consequences.
全球咖啡市场相互关联；国内税收可能会刺激从环保标准较低的国家进口，导致碳泄漏。这需要国际协调。考试中的评价必须权衡利弊，并展示对意外后果的意识。
Alternative policies include information campaigns to shift consumer preferences, cap-and-trade schemes for CO₂ emissions, and direct regulation of farming practices. Each has different cost-effectiveness and feasibility. In a 9-mark evaluation question, structure your answer to discuss one or two alternatives, using real-world examples where possible.
替代政策包括改变消费者偏好的信息宣传活动、二氧化碳排放的总量控制与交易制度，以及对种植过程的直接监管。每种政策有不同的成本效益与可行性。在回答 9 分评价题时，组织你的答案，讨论一两个替代方案，尽可能结合现实例子。
9. Connecting to Macroeconomic Objectives | 联系宏观经济目标
Coffee is a major export for developing countries like Ethiopia and Vietnam. Changes in the global coffee price affect their macroeconomic indicators. A price hike improves the current account balance through higher export revenue, potentially leading to economic growth and lower unemployment on coffee plantations. However, it may also create inflationary pressure if the economy approaches full capacity.
咖啡是埃塞俄比亚和越南等发展中国家的主要出口产品。全球咖啡价格的变动会影响其宏观经济指标。价格上涨通过增加出口收入改善经常账户平衡，可能促进经济增长并降低种植园失业。然而，如果经济接近充分产能，也可能带来通胀压力。
Conversely, when the price falls, export earnings shrink, worsening the trade balance. Governments may devalue their currency to restore competitiveness, but that can raise imported input costs. A diversified economy is less vulnerable; thus, many coffee-dependent nations aim to add value through processing before export.
相反，价格下跌时，出口收入萎缩，贸易差额恶化。政府可能贬值本币以恢复竞争力，但这会提高进口投入品的成本。经济多元化可降低脆弱性；因此，许多依赖咖啡的国家力求通过加工环节在出口前提升附加值。
In a case study linking micro and macro, you could discuss how a subsidy to organic coffee may affect GDP growth positively in the short run, but its impact on fiscal deficit might crowd out private investment. Always connect the dots between micro policy tools and macroeconomic outcomes.
在联系微观与宏观的案例中，你可以讨论有机咖啡补贴在短期内如何正向促进 GDP 增长，但其对财政赤字的影响可能会挤出私人投资。始终要把微观政策工具与宏观经济结果联系起来。
10. Exam-Style Questions and Techniques | 考试题型与技巧
Let’s practise with typical OCR case-study questions:
让我们用典型的 OCR 案例分析题来练习：
- Explain, using a demand and supply diagram, why the price of coffee beans rose after the frost. (5 marks)
- 使用需求与供给图，解释霜冻后咖啡豆价格为何上涨。（5分）
Approach: Draw a clear diagram showing leftward supply shift. Annotate P1,Q1 and P2,Q2. Explain that the frost reduced supply, creating a shortage at the original price, so price is bid up until the new equilibrium is reached. Use the case-study data to support the chain of reasoning.
答题方法：画一个清晰的图示显示供给曲线左移。标注 P1、Q1 和 P2、Q2。解释霜冻减少了供给，在原价格上形成短缺，因此价格被推高直至到达新均衡。运用案例数据支撑推理链条。
- Calculate the PED for coffee when the price rises from $3.00 to $3.60 and quantity demanded falls from 100 to 80 million bags. Comment on its significance for total revenue. (5 marks)
- 计算当价格从 3.00 美元升至 3.60 美元、需求量从 1 亿袋降至 8000 万袋时咖啡的需求价格弹性。评论其对总收益的意义。（5分）
Step-by-step: %ΔQd = (80-100)/100 × 100 = -20%; %ΔP = (3.60-3.00)/3.00 × 100 = 20% stays constant (or nearly so given rounding). Relate this to the firm’s pricing strategy.
逐步解答：%ΔQd = (80-100)/100 × 100 = -20%; %ΔP = (3.60-3.00)/3.00 × 100 = 20%; PED = -1。因为单位弹性，总收益保持恒定（或由于取整近似恒定）。将其与企业的定价策略相关联。
- Evaluate the government’s decision to impose a specific tax on coffee. Include diagrams and consider different stakeholders. (9 marks)
- 评价政府对咖啡征收从量税的决策。包含图示并考虑不同利益相关者。（9分）
Structure: Define specific tax; show rightward supply shift in diagram; explain tax incidence; calculate tax revenue and deadweight loss. Then evaluate: regressive impact on poor, possible health benefits, effect on farmers’ incomes, substitution effect to tea, and cross-border shopping. Conclude whether the tax is justified overall.
结构：定义从量税；在图中展示供给曲线向上移动；解释税收归宿；计算税收收入与无谓损失。然后评价：对穷人的累退影响、可能的健康益处、对农民收入的影响、转向茶的替代效应以及跨境购物。最后判断总体是否合理。
Always use connectives like ‘this means that’, ‘as a result’, and ‘however’ to build coherent explanations. Time management is crucial—spend about 1.5 minutes per mark. Practise under timed conditions with fresh articles to simulate the real exam.
始终使用“这意味着”、“因此”和“然而”等连接词构建连贯的解释。时间管理至关重要——大约每分值 1.5 分钟。使用新文章在限时条件下练习，以模拟真实考试。
Published by TutorHao | Economics Revision Series | aleveler.com
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