📚 GCSE AQA Economics: Oligopoly | GCSE AQA 经济：寡头 考点精讲
In GCSE Economics, understanding different market structures is crucial. Oligopoly is one of the most common market structures in the real world, where a few powerful firms dominate the market. This revision note covers the key characteristics of oligopoly, how firms behave, and the impact on consumers and efficiency.
在GCSE经济学中，理解不同的市场结构至关重要。寡头是现实世界中最常见的市场结构之一，少数几家强大的企业主导市场。本复习笔记涵盖寡头的关键特征、企业行为方式以及对消费者和效率的影响。
1. What is an Oligopoly? | 什么是寡头市场？
An oligopoly is a type of market structure where a small number of large firms control the majority of the market share. These firms are price makers rather than price takers, and their decisions are highly interdependent. Typical examples include the UK supermarket sector (Tesco, Sainsbury’s, Asda, Morrisons), the mobile phone network providers, and the banking industry.
寡头是一种市场结构，少数几家大企业控制着绝大部分市场份额。这些企业是价格制定者而非价格接受者，它们的决策高度相互依赖。典型例子包括英国超市业（Tesco、Sainsbury’s、Asda、Morrisons）、移动通信网络提供商和银行业。
Economists measure market concentration using concentration ratios, such as the five-firm concentration ratio. A high concentration ratio (e.g., above 60%) indicates an oligopolistic market. In the UK, the Competition and Markets Authority (CMA) monitors markets to prevent anti-competitive practices.
经济学家使用集中度比率（如五企业集中度比率）来衡量市场集中程度。高集中度比率（例如高于60%）表明市场是寡头垄断的。在英国，竞争与市场管理局（CMA）监控市场以防止反竞争行为。
2. Key Features of Oligopoly Markets | 寡头市场的关键特征
Oligopoly markets share several defining features: a few dominant firms, high barriers to entry, differentiated or homogeneous products, and mutual interdependence. Firms are aware of their rivals’ actions and may engage in strategic behaviour to protect their market position.
寡头市场具有几个典型特征：少数主导企业、高进入壁垒、差异化或同质化产品以及相互依赖。企业意识到竞争对手的行动，并可能采取策略性行为来保护自己的市场地位。
Products in an oligopoly can be virtually identical, like steel or petrol, or differentiated through branding, as in the car and smartphone industries. This differentiation allows firms to build brand loyalty and reduce direct price competition.
寡头中的产品可以几乎完全相同，如钢铁或汽油，也可以通过品牌实现差异化，就像汽车和智能手机行业那样。差异化使企业能够建立品牌忠诚度并减少直接的价格竞争。
3. Barriers to Entry | 进入壁垒
High barriers to entry are a fundamental reason why oligopolies persist. Barriers can include large start-up costs, economies of scale, control over essential resources, brand loyalty, and legal barriers such as patents or licences. These obstacles prevent new competitors from entering the market easily and competing away abnormal profits.
高进入壁垒是寡头持续存在的根本原因。壁垒可包括庞大的启动成本、规模经济、对关键资源的控制、品牌忠诚度以及专利或许可证等法律壁垒。这些障碍阻止新竞争者轻松进入市场并消除超额利润。
For instance, entering the commercial aircraft industry requires billions of pounds in investment and advanced technology, giving Boeing and Airbus significant market power. Similarly, supermarket chains benefit from bulk-buying discounts that new entrants cannot match.
例如，进入商用飞机行业需要数十亿英镑的投资和先进技术，这使得波音和空客拥有巨大的市场力量。同样，连锁超市从大批量采购折扣中获益，这是新进入者无法匹敌的。
4. Interdependence and Strategic Behaviour | 相互依赖与策略行为
A unique feature of oligopoly is that each firm’s decisions affect, and are affected by, the decisions of its rivals. This mutual interdependence means a firm cannot set prices or output without considering the likely reactions of competitors. This often leads to strategic behaviour where firms try to anticipate and react to rivals’ moves.
寡头的一个独特特征是每家企业的决策都会影响竞争对手并被竞争对手的决策影响。这种相互依赖意味着企业在制定价格或产量时不能不考虑竞争对手可能的反应。这通常导致策略性行为，即企业试图预测并应对对手的行动。
For example, if Tesco reduces the price of its basic food range, Sainsbury’s and Asda may quickly follow to avoid losing market share. Such tit-for-tat behaviour can lead to price wars or, alternatively, a stable pricing environment where all firms avoid aggressive price cuts.
例如，如果Tesco降低其基本食品系列的价格，Sainsbury’s和Asda可能会迅速跟进以避免市场份额损失。这种以牙还牙的行为可能导致价格战，或者形成一种稳定的定价环境，所有企业都避免激进降价。
5. The Kinked Demand Curve and Price Rigidity | 弯折的需求曲线与价格刚性
The kinked demand curve theory helps explain why prices in oligopolistic markets tend to be stable or ‘sticky’. It assumes that if a firm raises its price, rivals will not follow, so the firm loses many customers; demand is elastic above the current price. If a firm lowers its price, rivals will match the cut to protect their market share, so the firm gains few extra customers; demand is inelastic below the current price. The demand curve therefore has a ‘kink’ at the prevailing price, and the firm has little incentive to change price.
弯折的需求曲线理论有助于解释为什么寡头市场中的价格往往稳定或’粘性’。该理论假设如果一家企业提价，对手不会跟随，因此该企业会失去大量顾客；在当前价格之上，需求富有弹性。如果一家企业降价，竞争对手也会跟着降价以保护市场份额，因此这家企业只能获得极少的额外顾客；在当前价格之下，需求缺乏弹性。因此需求曲线在现行价格处出现’弯折’，企业几乎没有改变价格的动机。
This price rigidity means that non-price competition becomes vital, as firms cannot compete effectively on price alone. Even if costs rise or fall moderately, firms may keep prices unchanged to avoid triggering a price war or an unfavourable reaction from rivals.
这种价格刚性意味着非价格竞争变得至关重要，因为企业无法仅靠价格进行有效竞争。即使成本温和上升或下降，企业也可能保持价格不变，以避免引发价格战或竞争对手的不利反应。
6. Non-Price Competition | 非价格竞争
Because price competition is often risky in an oligopoly, firms invest heavily in non-price competition. This includes advertising, branding, product quality improvements, loyalty schemes, exclusive deals, customer service, and packaging. The goal is to differentiate the product and build a loyal customer base without altering the price.
由于在寡头中价格竞争往往具有风险，企业大量投资于非价格竞争。这包括广告、品牌建设、产品质量改进、忠诚度计划、独家交易、客户服务和包装。目标是在不改变价格的情况下实现产品差异化并建立忠实的客户基础。
Examples are everywhere: supermarkets offer clubcard points and home delivery services; mobile networks provide free data upgrades and handset bundles; car manufacturers distinguish their models through design, safety features and after-sales care. Non-price competition can increase choice and quality for consumers, but may also lead to wasteful duplication of marketing expenditure.
例子随处可见：超市提供会员积分和送货服务；移动网络提供免费流量升级和手机套装；汽车制造商通过设计、安全功能和售后服务来区分车型。非价格竞争可以增加消费者的选择和质量，但也可能导致营销支出上的浪费性重复。
7. Collusion and Cartels | 共谋与卡特尔
Oligopolistic firms may collaborate rather than compete, engaging in collusion. Collusion occurs when firms make secret or open agreements to fix prices, limit output, or divide markets, essentially acting like a monopoly to maximise joint profits. A formal agreement is known as a cartel. OPEC, the oil producers’ group, is a well-known example, although its effectiveness varies.
寡头企业可能合作而非竞争，即进行共谋。共谋发生在企业达成秘密或公开协议以固定价格、限制产量或瓜分市场，本质上像垄断者一样行动以最大化联合利润。正式协议被称为卡特尔。石油输出国组织(OPEC)是一个著名的例子，尽管其有效性有所不同。
In the UK and most developed economies, such practices are illegal under competition law. The CMA can impose heavy fines on firms found guilty of collusion, including criminal sanctions. Tacit collusion is more subtle where firms implicitly understand not to compete aggressively, without a formal agreement, which is harder to prove.
在英国和大多数发达经济体，此类操作根据竞争法是非法的。CMA可以对被发现犯有共谋的公司处以巨额罚款，包括刑事制裁。默契共谋则更为微妙，企业默示地理解不要激烈竞争，没有正式协议，这更难证明。
8. Game Theory: The Prisoner’s Dilemma | 博弈论：囚徒困境
Game theory provides a useful framework for analysing interdependence in oligopoly. The most famous example is the prisoner’s dilemma. Imagine two firms (A and B) considering whether to launch a price war. If both keep prices high (co-operate), they each earn high profits, say £10m. If one undercuts the price while the other keeps price high, the undercutter earns £15m and the other gets only £2m. If both cut prices (compete), profits fall to £4m each. This can be summarised in a payoff table:
博弈论为分析寡头中的相互依赖提供了有用的框架。最著名的例子是囚徒困境。假设两家企业（A和B）在考虑是否发动价格战。如果双方都保持高价（合作），各赚取高额利润，比如1000万英镑。如果一方降价而另一方保持高价，降价者赚取1500万英镑，另一方仅赚200万英镑。如果双方都降价（竞争），利润各降至400万英镑。这可以总结在收益表中：
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