Oligopoly in IGCSE Economics | IGCSE 经济：寡头考点精讲

📚 Oligopoly in IGCSE Economics | IGCSE 经济：寡头考点精讲

Oligopoly is one of the most fascinating market structures in IGCSE Economics. It is a market dominated by a few large firms, where each firm’s decisions directly affect its rivals. Understanding oligopoly is crucial because many real-world industries, from smartphone manufacturing to petrol retailing, operate under this structure. The interdependence of firms leads to strategic behaviour, making oligopoly distinct from perfect competition or monopoly. This article unpacks all the key concepts, diagrams and evaluation points you need to master for your IGCSE examination.

寡头垄断是IGCSE经济学中最引人入胜的市场结构之一。这是一个由少数几家大企业主导的市场，每家企业的决策都会直接影响其竞争对手。理解寡头之所以重要，是因为许多现实世界的行业，从智能手机制造到汽油零售，都在这种结构下运作。企业间的相互依存导致了策略性行为，使得寡头不同于完全竞争或垄断。本文将为你逐一剖析掌握IGCSE考试所需的所有关键概念、图表和评估点。

1. Definition and Characteristics of Oligopoly | 寡头的定义与特征

An oligopoly is a market structure where a few large firms have the majority of market share. The most distinctive feature is interdependence: the actions of one firm will directly affect the others. Products can be homogeneous (like steel or oil) or differentiated (like cars or soft drinks). There are high barriers to entry, such as huge capital costs, brand loyalty, and economies of scale. Firms are price makers but must consider rivals’ reactions before changing prices.

寡头是一种少数几家大企业占有大部分市场份额的市场结构。最突出的特征是相互依存：一家企业的行为会直接影响其他企业。产品可以是同质的（如钢铁或石油），也可以是差异化的（如汽车或软饮料）。存在高进入壁垒，例如巨大的资本成本、品牌忠诚度和规模经济。企业是价格制定者，但在改变价格前必须考虑竞争对手的反应。

2. Concentration Ratios | 集中度比率

Economists measure the degree of market power in an oligopoly using concentration ratios. The most common is the five-firm concentration ratio (CR5), which adds up the market share of the five largest firms. A CR5 above 60% typically indicates a tight oligopoly. The Herfindahl-Hirschman Index (HHI) is another tool, calculated by squaring the market share of each firm and summing them. A higher HHI suggests less competition.

经济学家使用集中度比率来衡量寡头垄断的市场力量程度。最常用的是五企业集中度比率（CR5），即前五大企业的市场份额总和。CR5超过60%通常表明是紧密的寡头垄断。赫芬达尔-赫希曼指数（HHI）是另一个工具，通过将每家企业的市场份额平方后求和计算得到。HHI越高说明竞争越少。

Firm	Market Share (%)
A	35
B	25
C	10
D	8
E	7
Others	15

For this industry, CR5 = 35 + 25 + 10 + 8 + 7 = 85%, indicating a highly concentrated market. The HHI would be 35² + 25² + 10² + 8² + 7² + (sum of squares of others) = 1225 + 625 + 100 + 64 + 49 + … , which exceeds 2000, signifying high concentration.

对于这个行业，CR5 = 35 + 25 + 10 + 8 + 7 = 85%，表明市场高度集中。HHI会是35² + 25² + 10² + 8² + 7² + (其他企业平方和) = 1225 + 625 + 100 + 64 + 49 + …，超过2000，同样意味着高集中度。

3. Non-price Competition | 非价格竞争

Because price wars can be mutually destructive, oligopolists often compete through non-price methods. This includes advertising, branding, loyalty schemes, product quality improvements, packaging, and after-sales service. Non-price competition aims to increase brand loyalty and make demand more price inelastic. It can also create barriers to entry by raising the cost of entry for potential rivals. However, excessive advertising can be wasteful and raise average costs.

由于价格战可能相互破坏，寡头企业通常通过非价格方法竞争。这包括广告、品牌建设、忠诚计划、产品质量提升、包装和售后服务。非价格竞争旨在增强品牌忠诚度，使需求更加缺乏价格弹性。它还可以通过提高潜在对手的进入成本来创造进入壁垒。然而，过度广告可能是浪费并抬高平均成本。

4. Collusion and Cartels | 勾结与卡特尔

Firms in an oligopoly may decide to collude rather than compete. Collusion can be formal (a cartel) or tacit (informal, unspoken agreement). A cartel involves firms agreeing on prices, output quotas, or market sharing to maximise joint profits as if they were a monopoly. The most famous example is OPEC. Collusion aims to reduce uncertainty and increase profits. However, cartels are often unstable because members have an incentive to cheat by secretly lowering prices or increasing output, especially when the good is homogeneous and monitoring is difficult.

寡头中的企业可能决定勾结而不是竞争。勾结可以是正式的（卡特尔）或默契的（非正式、心照不宣的协议）。卡特尔涉及企业就价格、产量配额或市场分享达成协议，以最大化联合利润，仿佛它们是一个垄断者。最著名的例子是石油输出国组织（OPEC）。勾结旨在减少不确定性并增加利润。然而，卡特尔通常不稳定，因为成员有动机通过秘密降价或增加产量来欺骗，尤其是在产品同质且监督困难的情况下。

In many countries, formal collusion is illegal due to its negative effect on consumer welfare. Competition authorities such as the CMA in the UK can impose heavy fines on firms found to be operating a cartel.

在许多国家，由于对消费者福利的负面影响，正式勾结是违法的。竞争监管机构，如英国的CMA，可以对被发现运作卡特尔的企业处以巨额罚款。

5. Game Theory and the Prisoner’s Dilemma | 博弈论与囚徒困境

Game theory analyses strategic interactions between firms. The prisoner’s dilemma is a classic example. Two firms (A and B) must decide whether to set a high price (cooperate) or a low price (cheat). If both charge a high price, they share high profits. If one cheats while the other charges high, the cheater gains market share and its profit rises, while the high-price firm loses. If both cheat, they both suffer low profits. The dominant strategy for each firm is to cheat, leading to a worse collective outcome—an equilibrium known as the Nash equilibrium.

博弈论分析企业之间的策略互动。囚徒困境是一个经典例子。两家企业（A和B）必须决定是设定高价（合作）还是低价（欺骗）。如果都定高价，它们分享高利润。如果一方欺骗而另一方定高价，欺骗者获得市场份额，利润上升，而高价企业受损。如果双方都欺骗，则都只能获得低利润。每家企业的主导策略是欺骗，导致更糟糕的集体结果——这种均衡称为纳什均衡。

	B: High Price	B: Low Price
A: High Price	(10, 10)	(2, 15)
A: Low Price	(15, 2)	(5, 5)

Payoffs are in millions of dollars. If A thinks B will charge high, A’s best response is low (15 > 10). If A thinks B will charge low, A’s best response is still low (5 > 2). The same logic applies to B. Thus (Low, Low) is the Nash equilibrium, even though both would be better off with (High, High). This explains why price wars can break out despite the benefit of collusion.

收益以百万美元计。如果A认为B会定高价，A的最佳回应是低价（15 > 10）。如果A认为B会定低价，A的最佳回应仍是低价（5 > 2）。同样的逻辑适用于B。因此（低价，低价）是纳什均衡，尽管（高价，高价）对双方都更好。这就解释了为什么尽管合谋有利，价格战仍可能爆发。

6. The Kinked Demand Curve and Price Rigidity | 弯折的需求曲线与价格刚性

The kinked demand curve model attempts to explain why prices are often stable in oligopolistic markets without explicit collusion. The firm faces a demand curve that is relatively elastic above the current price and relatively inelastic below it. This is because rivals will not match a price increase (they hope to gain customers) but will match a price cut (to avoid losing market share). As a result, the marginal revenue curve has a vertical discontinuity. Cost changes within that gap will not lead to a price change, implying price rigidity.

弯折的需求曲线模型试图解释为何在寡头市场中，价格常常在没有明确勾结的情况下保持稳定。企业面临的需求曲线在当前价格以上相对富有弹性，在当前价格以下相对缺乏弹性。这是因为竞争对手不会跟随提价（他们希望获得顾客），但会跟随降价（以避免失去市场份额）。因此，边际收益曲线出现垂直间断。在这个间断范围内的成本变化不会导致价格变化，从而表现出价格刚性。

Demand: Above P₀, PED > 1; Below P₀, PED < 1. MR curve is discontinuous. MC shifts within the gap → P and Q unchanged.

需求：P₀之上，PED > 1；P₀之下，PED < 1。MR曲线间断。MC在间断内移动 → 价格和产量不变。

Critics argue the model does not explain how the initial price is set. Nonetheless, it is a useful starting point for understanding non-collusive oligopoly behaviour in IGCSE.

批评者认为该模型未能解释初始价格是如何确定的。尽管如此，它仍是理解IGCSE中非合谋寡头行为的有用起点。

7. Oligopoly and Economic Efficiency | 寡头与经济效率

Compared to perfect competition, oligopoly tends to be less efficient. Allocative efficiency (P = MC) is unlikely because firms have market power and set prices above marginal cost. Productive efficiency (minimum AC) is not guaranteed, as firms may have spare capacity due to non-price competition or lack of competitive pressure. However, oligopolists can achieve dynamic efficiency through supernormal profits reinvested into research and development (R&D). This can lead to innovation and lower costs in the long run, benefitting consumers.

与完全竞争相比，寡头往往效率较低。配置效率（P = MC）不太可能实现，因为企业拥有市场力量，将价格设定在边际成本之上。生产效率（最低AC）没有保证，因为非价格竞争或缺乏竞争压力可能导致产能过剩。然而，寡头可以通过将超额利润再投资于研发（R&D）来实现动态效率。长期来看，这可能带来创新和更低的成本，使消费者受益。

In an IGCSE exam, you should be able to compare efficiencies across different market structures and evaluate whether oligopoly outcomes are necessarily bad for society.

在IGCSE考试中，你应该能够比较不同市场结构的效率，并评估寡头结果是否一定对社会不利。

8. Advantages of Oligopoly | 寡头的优点

Oligopolies can benefit society in several ways. Supernormal profits finance R&D, leading to technological progress and better products. Large-scale production allows economies of scale, potentially lowering average costs over time. Non-price competition may improve product quality and variety. Moreover, oligopolies can afford to undertake large, risky projects, such as new pharmaceutical drugs or renewable energy technology, which smaller firms cannot. In some cases, price stability can help consumers and firms plan ahead.

寡头可以在多个方面造福社会。超额利润为研发提供资金，带来技术进步和更好的产品。大规模生产实现规模经济，有可能随时间降低平均成本。非价格竞争可以改善产品质量和多样性。此外，寡头有能力承担大型、有风险的项目，例如新药或可再生能源技术，而小企业无法做到。在某些情况下，价格稳定有助于消费者和企业提前规划。

9. Disadvantages of Oligopoly | 寡头的缺点

On the other hand, oligopolies can exploit consumers by charging higher prices and restricting output compared to competitive markets. They may engage in wasteful non-price competition, such as excessive packaging or advertising, which raises costs without adding real value. Collusion reduces consumer choice and creates deadweight welfare loss. High barriers to entry stifle entrepreneurship and allow inefficiency to persist. If firms focus too much on takeovers rather than innovation, dynamic efficiency may be limited.

另一方面，与竞争市场相比，寡头可能通过收取更高价格和限制产量来剥削消费者。他们可能进行浪费性的非价格竞争，如过度包装或广告，这增加了成本却没有增加实际价值。勾结减少了消费者选择，造成无谓福利损失。高进入壁垒抑制了创业，使低效率持续存在。如果企业过于关注收购而非创新，动态效率可能受限。

10. Real-world Examples | 现实中的例子

Common examples include the supermarket industry (Tesco, Sainsbury’s, Asda, Morrisons in the UK), mobile phone services (Vodafone, EE, O2), banking, airline manufacturing (Boeing and Airbus), and petrol companies. In the soft drink market, Coca-Cola and PepsiCo form a duopoly—a special case of oligopoly with two dominant firms. These examples help illustrate concentration ratios, non-price competition, and interdependence. Students should learn to apply theory to specific cases in exam questions.

常见的例子包括超市行业（英国的Tesco、Sainsbury’s、Asda、Morrisons）、移动电话服务（Vodafone、EE、O2）、银行业、飞机制造（波音和空客）以及石油公司。在软饮料市场，可口可乐和百事可乐形成双头垄断——一种只有两家主导企业的特殊寡头。这些例子有助于说明集中度比率、非价格竞争和相互依存。学生应学会在考题中将理论应用于具体案例。

11. Exam Tips for Oligopoly | 考试技巧

For IGCSE, you must be able to define oligopoly, explain key characteristics, interpret concentration ratios, draw and explain the kinked demand curve, and discuss the prisoner’s dilemma. Evaluation is essential: always consider both costs and benefits of oligopoly, and distinguish between collusive and non-collusive behaviour. Use diagrams such as the kinked demand curve and the prisoner’s dilemma payoff matrix. Answer questions with structured paragraphs and real-world references to show application.

IGCSE考试要求你能够定义寡头，解释关键特征，解读集中度比率，绘制并解释弯折的需求曲线，并讨论囚徒困境。评估至关重要：始终考虑寡头的成本和收益，区分勾结性与非勾结性行为。使用图表，如弯折的需求曲线和囚徒困境收益矩阵。用结构化的段落和现实世界的参考来回答问题，以展示应用能力。

Define key terms precisely.

精确定义关键术语。
Use the kinked demand curve to explain price stability.

运用弯折的需求曲线解释价格稳定性。
Link game theory to the risk of price wars.

将博弈论与价格战的风险联系起来。
Evaluate dynamic efficiency versus allocative inefficiency.

评估动态效率与配置无效。

12. Summary | 总结

Oligopoly is a realistic and complex market structure. It sits between perfect competition and monopoly, with features such as interdependence, non-price competition, potential collusion, and the possibility of both efficiency gains and losses. A deep understanding of these concepts and their application to real markets will enable you to score high marks on the IGCSE Economics paper. Always remember to balance your arguments and use economic terminology accurately.

寡头是一种现实而复杂的市场结构。它介于完全竞争和垄断之间，具有相互依存、非价格竞争、潜在勾结以及效率得失并存等特点。对这些概念及其在真实市场中的应用有深刻理解，将使你在IGCSE经济学试卷中获得高分。始终记住平衡你的论点，并准确使用经济术语。

Published by TutorHao | Economics Revision Series | aleveler.com

更多咨询请联系16621398022（同微信）

Oligopoly in IGCSE Economics | IGCSE 经济：寡头考点精讲