📚 GCSE Economics: Oligopoly Revision Notes | GCSE 经济：寡头考点精讲
An oligopoly is one of the most important market structures you will study in GCSE Economics. Unlike perfect competition or monopoly, oligopoly sits somewhere in the middle, with a small number of large firms dominating the market. This creates a unique set of behaviours, from fierce price wars to secret collusion, that affect consumers, businesses and the wider economy. Understanding the key characteristics, the kinked demand curve, game theory and the role of non‑price competition is essential for top marks in your exams.
寡头垄断是 GCSE 经济中最重要的市场结构之一。与完全竞争或垄断不同，寡头介于两者之间，由少数几家大企业支配市场。这创造出独特的企业行为，从激烈的价格战到秘密勾结，影响着消费者、企业和整体经济。掌握关键特征、拗折需求曲线、博弈论以及非价格竞争的作用，是考试取得高分的关键。
1. Definition and Key Features | 定义与核心特征
An oligopoly is a market dominated by a small number of large firms. The term comes from the Greek ‘oligos’ (few) and ‘polein’ (to sell). The most distinctive feature is interdependence: each firm’s decisions on price, output and advertising directly influence the others, so they must anticipate rivals’ reactions. Products may be homogeneous (e.g. steel, cement) or differentiated (e.g. cars, smartphones). The market is characterised by high barriers to entry, which protect the existing oligopolists.
寡头是由少数几家大企业主导的市场。’寡头’一词源自希腊语 ‘oligos’（少）和 ‘polein’（卖）。最显著的特征是相互依赖：每家企业在价格、产量和广告上的决策会直接影响对手，因此它们必须预判竞争对手的反应。产品可以是同质的（如钢铁、水泥），也可以是差异化的（如汽车、智能手机）。市场具有很高的进入壁垒，保护着现有的寡头企业。
2. Characteristics of Oligopoly | 寡头市场的特点
A small number of large firms control the bulk of market supply. The concentration ratio (e.g. the five‑firm ratio) is typically high, often above 50%. Each firm holds significant market power, enabling it to influence prices rather than simply taking the market price as given.
少数几家大企业控制着市场上的绝大部分供给。集中度比率（如五企业集中度）通常很高，常高于50%。每一家企业都拥有显著的市场支配力，能够影响价格，而不仅仅是接受市场既定价格。
Firms are mutually dependent, meaning that any price cut or advertising campaign by one firm will provoke a swift response from rivals. Rivals may match a price reduction but ignore a price increase, creating a strong incentive to avoid price competition.
企业彼此相互依存，这意味着任何一家企业降价或推出广告活动，都会立即引发竞争对手的反应。对手可能跟随降价，但对涨价置之不理，由此产生强烈的避免价格竞争的动机。
High barriers to entry, such as huge capital costs, economies of scale, brand loyalty and legal restrictions, prevent new firms from entering easily. Oligopolists can therefore sustain supernormal profits in the long run.
高昂的进入壁垒，如巨额资本投入、规模经济、品牌忠诚度和法律限制，使新企业难以轻松进入。因此，寡头企业能够在长期维持超额利润。
Non‑price competition is widespread. Firms rely heavily on advertising, product differentiation, packaging, after‑sales service and loyalty programmes to win market share without triggering a price war.
非价格竞争十分普遍。企业大量依赖广告、产品差异化、包装、售后服务和忠诚度计划来赢取市场份额，而不引发价格战。
3. Barriers to Entry in Detail | 进入壁垒详解
Economies of scale are a natural barrier: existing large firms produce at a low average cost, forcing a new entrant to start big or face a cost disadvantage. High sunk costs, such as spending on specialised machinery or R&D, deter entry because they cannot be recovered if the venture fails.
规模经济是一种天然壁垒：现有大企业以低平均成本生产，迫使新进入者要么大规模起步，要么承受成本劣势。高昂的沉没成本，如专用设备或研发支出，也阻碍进入，因为这些成本一旦失败便无法收回。
Brand loyalty and heavy advertising create a psychological barrier. Consumers trust well‑known brands, and a new firm would need enormous marketing budgets to shift buyer behaviour. Legal barriers, including patents, licences and government regulations, can grant exclusive rights to a few firms.
品牌忠诚度和大量广告形成了心理壁垒。消费者信赖知名品牌，新公司需要巨额营销预算才能改变购买习惯。法律壁垒，如专利、许可证和政府法规，可以授予少数企业独家经营权。
Threat of retaliation by existing oligopolists can be a powerful deterrent. Predatory pricing – deliberately lowering prices below cost to eliminate a newcomer – is a risky but possible strategy that makes entry unattractive.
现有寡头企业的报复威胁是一种强大的威慑。掠夺性定价——故意将价格降至成本以下以挤走新进入者——是一种有风险但可能的策略，使进入市场变得没有吸引力。
4. Interdependence and Price Rigidity | 相互依赖与价格刚性
Because firms are interdependent, they are acutely aware that changing price could start a price war. If Firm A cuts its price, rivals will follow to protect their sales, so Firm A only gains a small increase in quantity sold and its revenue may fall. If Firm A raises its price, rivals may not follow, so Firm A loses a large number of customers. This asymmetry discourages price changes, leading to price rigidity or stickiness.
由于企业相互依赖，它们十分清楚改变价格可能引发价格战。如果 A 公司降价，对手会跟随降价以保住销量，A 公司只能获得少量销量增长，收入还可能下降。如果 A 公司抬高价格，对手可能不跟随，A 公司就会失去大量客户。这种不对称性抑制了价格变动，导致价格刚性。
Firms have a strong incentive to keep price stable and instead compete through advertising, product improvement and other non‑price methods. Prices tend to remain constant for relatively long periods, even when costs change.
企业有强烈动机保持价格稳定，转而通过广告、产品改进等非价格手段竞争。价格往往在较长时期内保持不变，即便成本发生变化。
5. The Kinked Demand Curve | 拗折需求曲线
The kinked demand curve model explains price rigidity in oligopoly. It assumes that if a firm raises its price, rivals will not follow, so demand is elastic above the current price. If it lowers its price, rivals will match the cut, so demand is inelastic below the current price. The demand curve therefore has a ‘kink’ at the prevailing price.
拗折需求曲线模型解释了寡头市场中的价格刚性。它假设：如果一家企业提高价格，对手不会跟随，因此在当前价格之上需求富有弹性；如果它降低价格，对手会跟着降价，因此在当前价格之下需求缺乏弹性。于是需求曲线在当前价格处出现’拗折’。
Above P*: Elastic demand → price rise leads to large loss of customers
Below P*: Inelastic demand → price cut brings small gain in sales matched by rivals
P* 之上：需求有弹性 → 提价导致大量客户流失
P* 之下：需求缺乏弹性 → 降价只获得少量销量增加，且被对手模仿
The marginal revenue curve becomes discontinuous, with a vertical gap. Even if marginal cost shifts within that gap, the profit‑maximising price (where MR = MC) remains unchanged. This reinforces price stability.
边际收益曲线出现不连续，形成一个垂直缺口。即便边际成本在这个缺口范围内变动，利润最大化价格（MR = MC 处）仍然不变，这进一步强化了价格稳定。
6. Non‑price Competition | 非价格竞争
Instead of competing on price, oligopolists invest heavily in non‑price competition. Heavy brand advertising creates an emotional connection with consumers and builds brand loyalty, making demand less price elastic. Frequent launches of new models or features distinguish products from rivals.
寡头企业不在价格上竞争，而是大力投入非价格竞争。大量的品牌广告与消费者建立情感联系，建立品牌忠诚度，使需求的价格弹性降低。频繁推出新型号或新功能，使产品区别于对手。
Customer service, extended warranties, loyalty cards and exclusive after‑sales support are also widely used. Such strategies increase costs but can strengthen market power and justify a premium price without triggering a direct price war.
客户服务、延长保修、积分卡和专属售后支持也被广泛使用。这些策略会增加成本，但能够增强市场支配力，支撑更高的溢价，同时避免直接价格战。
Product quality and innovation become critical. For example, smartphone manufacturers compete by offering better cameras, longer battery life or unique software features rather than slashing prices.
产品质量和创新变得至关重要。例如，智能手机制造商通过提供更好的摄像头、更长的电池寿命或独特的软件功能来竞争，而不是大幅降价。
7. Game Theory and the Prisoner’s Dilemma | 博弈论与囚徒困境
Oligopoly behaviour can be analysed using game theory. The most famous example is the prisoner’s dilemma, where two suspects would both be better off cooperating (staying silent) but each rationally chooses to confess because they fear the other will confess first. Applied to firms, both would earn higher profits if they kept prices high (cooperate), but each is tempted to lower price to steal market share, fearing the rival may do the same.
寡头行为可以用博弈论分析。最著名的例子是囚徒困境：两个嫌犯如果合作（保持沉默）对双方更有利，但每个人都会理性地选择坦白，因为害怕对方先坦白。套用到企业，双方若都维持高价（合作）可获得更高利润，但每家都受到降价抢占份额的诱惑，并担心对手会这么做。
Payoff matrix (profits in £ million): Firm A and Firm B choose High or Low price
收益矩阵（利润，百万英镑）：A 公司与 B 公司选择高价或低价
| B: High Price | B: Low Price | |
|---|---|---|
| A: High Price | A: 10, B: 10 | A: 3, B: 15 |
| A: Low Price | A: 15, B: 3 | A: 5, B: 5 |
Each firm’s dominant strategy is to choose a low price, leading to a Nash equilibrium where both earn only 5, even though they could have earned 10 by both choosing high price. This shows how interdependence can lead to sub‑optimal outcomes, but also explains why price wars sometimes break out in oligopoly.
每家企业的占优策略是选择低价，导致纳什均衡下双方只赚 5，而如果双方都选高价本可赚 10。这表明相互依赖会导致次优结果，也解释了为何寡头市场有时会爆发价格战。
8. Collusion and Cartels | 勾结与卡特尔
To avoid the damaging effects of price competition, oligopolists may collude – secretly agree on prices, output or market shares. When collusion is formal and open, it forms a cartel. The most famous example is OPEC, where oil‑producing nations agree on production quotas to influence global oil prices.
为避免价格竞争的不利影响，寡头企业可能勾结——秘密商定价格、产量或市场份额。当勾结正式且公开时，就形成了卡特尔。最著名的例子是欧佩克（OPEC），产油国通过商定产量配额来影响全球油价。
Collusion allows firms to act like a monopoly, pushing prices up and output down, earning higher joint profits. In most countries, however, explicit collusion is illegal because it harms consumers and reduces allocative efficiency. Competition authorities, such as the UK’s CMA, can impose heavy fines.
勾结使企业可以像垄断方一样行动，抬高价格、压低产量，获取更高的联合利润。但在大多数国家，公开勾结是非法的，因为它损害消费者利益并降低配置效率。英国竞争与市场管理局（CMA）等监管机构可处以高额罚款。
Tacit collusion is trickier to regulate: firms do not communicate directly but follow an unwritten understanding, such as following the pricing lead of a dominant firm (price leadership) without any formal agreement.
默契勾结更难监管：企业并不直接沟通，而是遵循不成为文的默契，如在没有任何正式协议的情况下，跟随主导企业的定价（价格领导制）。
9. Oligopoly and Efficiency | 寡头与效率
Allocative efficiency (price equals marginal cost) is unlikely in oligopoly. Prices tend to be above marginal cost, indicating under‑production and a welfare loss. Productive efficiency (producing at minimum average cost) may also not be achieved because of excess capacity from non‑price competition or deliberate under‑utilisation to create scarcity.
寡头市场中配置效率（价格等于边际成本）不太可能实现。价格往往高于边际成本，表明生产不足和社会福利损失。生产效率（以最低平均成本生产）也可能无法达到，因为非价格竞争导致产能过剩，或者企业故意低负荷运转以制造稀缺。
However, oligopolists often benefit from significant economies of scale, pushing average costs lower than would be possible in more fragmented markets. Dynamic efficiency may be high: supernormal profits provide the funds and incentive for investment in R&D and innovation, benefiting consumers in the long run.
然而，寡头企业往往享有显著的规模经济，使平均成本低于更分散的市场。动态效率可能较高：超额利润为研发和创新提供了资金与激励，长期使消费者受益。
Thus the efficiency picture is mixed. While static efficiency suffers, dynamic gains can offset some of the deadweight loss.
因此效率状况是混合的。虽然静态效率受损，但动态收益可以抵消部分无谓损失。
10. Evaluating Oligopoly Markets | 评估寡头市场
Oligopoly has both costs and benefits. On the negative side, higher prices and restricted output harm consumers, especially lower‑income households. Reduced choice in some markets and the danger of collusion raise equity and welfare concerns. On the positive side, intense non‑price competition can result in rapid innovation, better quality and a wide range of products.
寡头垄断有利有弊。负面来看，较高的价格和受限的产量损害消费者，特别是低收入家庭。某些市场选择减少和勾结风险引发公平与福利担忧。正面来看，激烈的非价格竞争可以带来快速创新、更高的质量和丰富的产品种类。
Employment effects can be mixed: large oligopolistic firms often provide stable, well‑paid jobs, but predatory actions against smaller rivals may reduce employment in some sectors. Government intervention, such as fines, breaking up cartels or promoting competition, tries to curb the worst abuses while retaining the benefits of scale and innovation.
就业效应也可能混合：大型寡头企业常常提供稳定、薪酬较好的工作，但针对小型竞争对手的掠夺性行为可能减少某些行业的就业。政府干预，如罚款、拆分卡特尔或促进竞争，力求遏制最恶劣的弊端，同时保留规模与创新的益处。
In an exam, you should be able to discuss both sides and reach a reasoned conclusion based on evidence. Use real‑world examples like supermarkets, mobile phone networks, banking or energy providers.
考试中，你需要能够讨论正反两面，并依据证据得出合理的结论。使用现实例子，如超市、移动通信网络、银行或能源供应商。
11. Exam Tips and Common Questions | 考试技巧与常见题型
You may be asked to ‘explain two features of oligopoly’ or ‘analyse why prices are stable in an oligopolistic market’. Always link your answer to interdependence and the kinked demand curve. For evaluation questions, discuss collusion, game theory and the difference between short‑run and long‑run outcomes.
你可能会被要求 ‘解释寡头的两个特征’ 或 ‘分析为何寡头市场中价格稳定’。回答时务必联系相互依赖和拗折需求曲线。评估类问题要讨论勾结、博弈论，以及短期与长期结果的区别。
Diagrams can earn high marks: sketch a kinked demand curve with a vertical gap in the MR curve, correctly labelled. A payoff matrix for prisoner’s dilemma is also powerful. Avoid vague statements – use precise terms like ‘interdependence’, ‘concentration ratio’ and ‘non‑price competition’.
图表能赢得高分：画一条拗折需求曲线，标注 MR 曲线的垂直缺口，并正确标明。囚徒困境的收益矩阵也同样有说服力。避免含混表述——使用精确术语，如 ‘相互依赖’、’集中度比率’、’非价格竞争’。
When using examples, be specific. Instead of just ‘supermarkets’, name a scenario: ‘If Tesco cut the price of bread, Sainsbury’s and Asda would likely match the cut to protect market share.’ This demonstrates real understanding.
使用例子时要具体。不要只说 ‘超市’，而是描述情景：’如果乐购降低面包价格，森宝利和阿斯达很可能跟进降价以保护市场份额。’ 这体现真正的理解。
12. Summary | 总结
Oligopoly is a market of few interdependent firms, high barriers and non‑price rivalry. Price rigidity is explained by the kinked demand curve, while game theory shows why collusion can break down into price wars. Although oligopoly can lead to higher prices and allocative inefficiency, it also drives innovation and economies of scale. Master these concepts, link them to real‑world examples, and you will excel in your GCSE Economics exam.
寡头是由少数相互依赖的企业、高壁垒和非价格竞争构成的市场。价格刚性可以通过拗折需求曲线解释，博弈论则展示了为何勾结会破裂并演变成价格战。尽管寡头可能导致高价和配置低效率，但它也推动创新和规模经济。掌握这些概念，并与现实例子相联系，你将在 GCSE 经济考试中表现出色。
Published by TutorHao | Economics Revision Series | aleveler.com
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