Oligopoly | 寡头 - aleveler.com

📚 Oligopoly | 寡头

Oligopoly is a market structure dominated by a small number of large firms, where each firm’s decisions are strategically interdependent. It lies between perfect competition and monopoly, characterised by high barriers to entry, product differentiation, and the potential for collusive or non-collusive behaviour. Understanding oligopoly is essential for analysing real-world markets such as supermarkets, car manufacturing, and energy suppliers.

寡头是由少数大型企业主导的市场结构，每个企业的决策在战略上相互依赖。它介于完全竞争和垄断之间，具有高进入壁垒、产品差异化以及存在合谋或非合谋行为的可能性。理解寡头市场对于分析现实世界中的市场至关重要，例如超市、汽车制造和能源供应。

1. Defining Oligopoly | 寡头市场的定义

Oligopoly refers to a market where a few firms account for a large share of total output. The concentration ratio, usually the five-firm or three-firm ratio, measures the combined market share of the largest firms. A high concentration ratio indicates an oligopolistic market structure.

寡头指的是少数几家企业在总产出中占据很大份额的市场。集中度比率，通常为五企业或三企业集中度比率，用于衡量最大几家企业的市场份额之和。高集中度比率表明市场结构为寡头垄断。

In the UK, an oligopoly is often identified when the five-firm concentration ratio exceeds 60%. However, concentration ratios can be misleading if the market is narrowly defined or if there is significant import penetration.

在英国，当五企业集中度比率超过60%时，通常可识别为寡头市场。然而，如果市场定义过窄或存在大量进口渗透，集中度比率可能会产生误导。

2. Characteristics of Oligopoly | 寡头市场的特征

Few dominant firms: The market is controlled by a small number of large firms, each with significant market power but not a monopoly.

少数主导企业：市场由少数几家大企业控制，每家企业都有显著的市场力量但不构成垄断。

High barriers to entry and exit: These include economies of scale, brand loyalty, patents, and high capital requirements, which prevent new firms from easily entering the market.

高进入与退出壁垒：包括规模经济、品牌忠诚度、专利和高资本要求，这些都阻止了新企业轻易进入市场。

Interdependence: The decisions of one firm directly affect the profits and strategy of rivals. This leads to strategic behaviour, making game theory a useful tool for analysis.

相互依赖：一家企业的决策直接影响到竞争对手的利润和战略。这导致了策略性行为，使得博弈论成为分析的有力工具。

Product differentiation: Products may be homogeneous (e.g., steel) or differentiated (e.g., cars, smartphones), often through branding and advertising.

产品差异化：产品可能是同质的（如钢铁）或差异化的（如汽车、手机），通常通过品牌和广告实现差异。

Non-price competition: Firms compete heavily on advertising, quality, loyalty schemes, and after-sales service rather than price, to avoid price wars.

非价格竞争：企业主要在广告、质量、忠诚度计划和售后服务方面展开激烈竞争，而非价格竞争，以避免价格战。

3. The Kinked Demand Curve | 拗折的需求曲线

The kinked demand curve model explains price rigidity in non-collusive oligopoly. It assumes that if a firm raises its price, rivals will not follow, causing a large loss of market share (elastic demand above the kink). If a firm lowers its price, rivals will match the cut to protect their market share, so the firm gains little extra demand (inelastic demand below the kink).

拗折的需求曲线模型解释了非合谋寡头市场中的价格刚性。该模型假设，如果一家企业提高价格，竞争对手不会跟随，导致其市场份额大幅损失（拗点以上的需求弹性较大）。如果一家企业降低价格，竞争对手会跟随降价以保护自己的市场份额，因此降价企业几乎不会增加需求（拗点以下的需求缺乏弹性）。

This results in a discontinuity in the marginal revenue curve. At the kink, marginal revenue is vertical, meaning marginal cost can change within a range without the profit-maximising price and output changing. Thus, prices remain stable.

这导致边际收益曲线出现一个断裂。在拗点处，边际收益垂直，意味着在某个区间内边际成本发生变化时，利润最大化的价格和产量却保持不变。因此，价格保持稳定。

The model helps explain why oligopoly prices are often sticky, but it has limitations: it does not explain how the initial price is set, and it assumes firms cannot learn through repeated interactions.

该模型有助于解释为什么寡头价格经常具有粘性，但它也有局限性：它无法解释最初的价格是如何设定的，并且假设企业无法通过反复互动中学习。

4. Collusive Oligopoly | 合谋寡头

Collusion occurs when firms in an oligopoly cooperate to reduce uncertainty and increase joint profits. Collusion can be formal (a cartel) or informal (tacit collusion). A cartel involves an explicit agreement to fix prices, limit output, or divide markets, which is illegal in many countries.

合谋发生在寡头企业为了减少不确定性和增加共同利润而合作时。合谋可以是正式的（卡特尔）或非正式的（默示合谋）。卡特尔涉及固定价格、限制产量或划分市场的明确协议，这在许多国家是非法的。

The Organisation of Petroleum Exporting Countries (OPEC) is a well-known example of a cartel. By restricting oil supply, OPEC members aim to raise the world price above the competitive level, earning supernormal profits.

石油输出国组织（欧佩克）是著名的卡特尔例子。通过限制石油供应，欧佩克成员力图将世界价格提高到竞争水平之上，从而赚取超额利润。

Tacit collusion involves firms following a recognised price leader or using complex signalling without explicit agreement. This helps maintain stable prices and avoid price wars.

默示合谋涉及企业跟随公认的价格领导者或利用复杂的信号传递，而无需明确协议。这有助于维持价格稳定并避免价格战。

Collusion is more likely when there are few firms, high barriers to entry, similar costs, homogenous products, and a stable market demand. Collusion can break down due to cheating incentives, antitrust intervention, or external shocks.

当企业数量少、进入壁垒高、成本结构相似、产品同质且市场需求稳定时，合谋更有可能发生。合谋可能因作弊激励、反垄断干预或外部冲击而瓦解。

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

Game theory analyses strategic interactions between firms where the outcome for each depends on the actions of all. In an oligopoly, firms are players, each choosing a strategy (e.g., high price or low price) to maximise profit.

博弈论分析企业之间的战略互动，其中一个企业的结果取决于所有企业的行动。在寡头市场中，企业是参与者，每家都选择一种策略（如高价或低价）以实现利润最大化。

The prisoner’s dilemma illustrates why collusion can be hard to sustain. Two firms have a dominant strategy to cheat (set a low price) even though mutual cooperation (high price) yields higher joint profits. The Nash equilibrium is where both firms set a low price, earning lower profits than if they cooperated.

囚徒困境说明了为什么合谋难以维持。两家企业都有占优策略进行作弊（设定低价），尽管相互合作（高价）能带来更高的共同利润。纳什均衡是两家都设定低价，获得比合作时更低的利润。

This helps explain non-collusive behaviour: the temptation to undercut rivals prevents stable collusion in many markets. However, under repeated games with the threat of retaliation (tit-for-tat), cooperation may emerge.

这有助于解释非合谋行为：降价抢走对手生意的诱惑，使许多市场中无法实现稳定的合谋。但在重复博弈中，由于报复的威胁（以牙还牙策略），合作可能会出现。

6. Price Leadership | 价格领导

Price leadership is a form of tacit collusion where one dominant firm (the price leader) sets a price, and other firms in the industry follow. This reduces uncertainty and avoids destructive price wars. There are two main types: dominant firm price leadership and barometric price leadership.

价格领导是默示合谋的一种形式，由一家主导企业（价格领导者）设定价格，行业内的其他企业跟随。这降低了不确定性并避免了破坏性的价格战。主要有两种类型：主导企业价格领导和晴雨表式价格领导。

Dominant firm price leadership occurs when the largest firm, often with the lowest costs, sets the profit-maximising price. Smaller firms act as price takers at that price, supplying the rest of the market demand.

主导企业价格领导发生在最大的企业（通常是成本最低的企业）设定利润最大化价格时。小企业在该价格下充当价格接受者，供应剩余的市场需求。

Barometric price leadership occurs when a firm is recognised as having good market insight and initiates price changes that others follow, without any single firm having dominant market share.

晴雨表式价格领导发生在某家企业被认为具有良好的市场洞察力并引导价格变动，其他企业跟随，而没有任何单一企业拥有主导市场份额。

7. Non-price Competition | 非价格竞争

Instead of competing on price, oligopolistic firms often engage in non-price competition to increase market share and build brand loyalty. This includes advertising, product innovation, packaging, quality improvement, and customer service.

寡头企业通常不通过价格竞争，而是进行非价格竞争，以增加市场份额和建立品牌忠诚度。这包括广告、产品创新、包装、质量改进和客户服务。

Heavy advertising can act as a barrier to entry by increasing the sunk costs needed for a new firm to establish a brand. It also shifts the firm’s demand curve to the right and makes it more inelastic, allowing higher prices.

大量广告可以通过增加新企业建立品牌所需的沉没成本而成为进入壁垒。它还将企业的需求曲线向右移动并使其更缺乏弹性，从而允许更高的定价。

Loyalty schemes, extended warranties, and free delivery are common in industries like supermarkets, airlines, and car manufacturing. These strategies can lead to allocative inefficiency because resources are used to differentiate products rather than lower prices.

在超市、航空公司和汽车制造等行业，忠诚度计划、延长保修和免费送货是常见做法。这些策略可能导致配置效率低下，因为资源被用于产品差异化而非降低价格。

8. Efficiency in Oligopoly | 寡头市场的效率

Oligopolies can result in both static and dynamic efficiencies or inefficiencies. Because firms have market power, they often produce where price exceeds marginal cost (P > MC), leading to allocative inefficiency. Productive efficiency (P = minimum ATC) may also be missed if firms have spare capacity or engage in extensive non-price competition.

寡头市场可能产生静态和动态的效率或不效率。由于企业拥有市场力量，它们通常在价格大于边际成本（P > MC）处生产，导致配置无效率。如果企业存在闲置产能或进行广泛的非价格竞争，也可能无法实现生产效率（P = 最低平均总成本）。

However, oligopolists may achieve dynamic efficiency by using supernormal profits to invest in research and development (R&D). This can lead to product innovation, better quality, and lower costs in the long run, benefiting consumers.

但寡头企业可能通过利用超额利润投资于研发（R&D）而实现动态效率。这可以带来产品创新、更好的质量以及更低的长期成本，从而惠及消费者。

X-inefficiency can arise when lack of competitive pressure allows costs to rise above minimum levels due to organisational slack. The net welfare effect of oligopoly depends on the balance between market power abuse and the benefits of innovation.

当缺乏竞争压力导致因组织松弛而使得成本高于最低水平时，就会出现X无效率。寡头对福利的净影响取决于滥用市场力量与创新收益之间的平衡。

9. Evaluation of Oligopoly | 寡头市场的评估

Evaluating oligopoly requires considering its effects on consumers, producers, and society. Key arguments in favour include:

Supernormal profits fund R&D, leading to technological progress.
Economies of scale can result in lower average costs than in more competitive markets.
Product variety and quality may increase consumer choice and welfare.

评估寡头市场需要考虑其对消费者、生产者和社会的影響。支持寡头的主要论点包括：

超额利润资助研发，带来技术进步。
规模经济可能导致平均成本低于更竞争性市场。
产品多样性和质量提高可能增加消费者选择与福利。

Arguments against oligopoly include:

Higher prices and restricted output reduce consumer surplus.
Allocative and productive inefficiency persist.
Barriers to entry reduce contestability and protect inefficient firms.
Massive advertising spending may be wasteful and mislead consumers.

反对寡头市场的论点包括：

更高的价格和受限的产量减少了消费者剩余。
配置和生产无效率持续存在。
进入壁垒降低了可竞争性，保护了效率低下的企业。
大量的广告支出可能是浪费且误导消费者。

10. Oligopoly and Contestable Markets | 寡头与可竞争市场

A market is contestable when entry and exit are costless, allowing potential competition to discipline incumbent firms even in an oligopoly. The threat of hit-and-run entry forces oligopolists to set prices close to average cost, reducing supernormal profits.

当进入和退出没有成本时，市场就是可竞争的，这使得潜在竞争即使在寡头市场也能约束在位企业。掠夺性进入的威胁迫使寡头企业将价格定在接近平均成本的水平，从而减少超额利润。

Sunk costs, which are irrecoverable if a firm leaves the market, are the main barrier to contestability. Low sunk costs make an oligopolistic market behave more competitively, improving allocative and productive efficiency.

沉没成本，即企业离开市场时无法收回的成本，是可竞争性的主要壁垒。低沉的沉没成本使寡头市场行为更具竞争性，改善了配置和生产效率。

Regulators may try to increase contestability by reducing sunk costs, improving information flows, and preventing anti-competitive practices. However, many real-world oligopolies remain far from perfectly contestable due to brand loyalty and scale economies.

监管者可能通过降低沉没成本、改善信息流通和防止反竞争行为来提高可竞争性。然而，由于品牌忠诚度和规模经济，许多现实世界中的寡头市场远非完全可竞争。

11. Game Theory Application: Advertising Decisions | 博弈论应用：广告决策

Consider two oligopolists, Firm A and Firm B, deciding whether to advertise heavily. If both advertise, they offset each other’s efforts and earn lower profits. If neither advertises, they save costs and earn moderate profits. If one advertises and the other does not, the advertiser gains market share at the rival’s expense.

考虑两家寡头企业 A 和 B，它们决定是否进行大量广告。若两者都做广告，彼此抵消，获得较低利润。若都不做广告，节省成本并获得中等利润。若一家做广告而另一家不做，做广告者以竞争对手的损失获得市场份额。

The payoff matrix often resembles the prisoner’s dilemma: the dominant strategy for each is to advertise, leading to a Nash equilibrium where both advertise, even though mutual non-advertising would be jointly better. This demonstrates how interdependence can lead to suboptimal outcomes.

支付矩阵通常类似于囚徒困境：每家的占优策略都是做广告，导致纳什均衡为两家都做广告，尽管都不做广告对双方会更好。这表明相互依赖如何导致次优结果。

In reality, repeated interactions and the threat of advertising wars may sustain tacit agreements to limit advertising expenditure, improving industry profitability.

在现实中，重复互动和广告战的威胁可能维持限制广告支出的默契协议，从而提高行业盈利能力。

12. Exam Tips for Oligopoly | 寡头考点的应试技巧

When answering exam questions on oligopoly, always define key terms and use a diagram where appropriate, such as the kinked demand curve. Evaluate by discussing collusive vs non-collusive outcomes, static vs dynamic efficiency, and the role of contestability.

在回答关于寡头的考试题目时，务必定义关键术语，并在适当时候使用图示，例如拗折的需求曲线。通过讨论合谋与非合谋结果、静态与动态效率以及可竞争性的作用进行评析。

Apply real-world examples: UK supermarkets (non-collusive oligopoly, price wars vs loyalty schemes), the US car industry, and the global smartphone market. Be ready to explain why prices are stable in some oligopolies but volatile in others.

应用现实世界的例子：英国超市（非合谋寡头，价格战与忠诚度计划）、美国汽车行业以及全球智能手机市场。准备解释为什么有些寡头市场价格稳定而另一些则波动。

Link to broader economic concepts: interdependence, the role of information, barriers to entry, and government competition policy. Use structured analysis with points for and against, followed by a justified conclusion.

联系更广泛的经济概念：相互依赖、信息的作用、进入壁垒以及政府竞争政策。采用结构化的分析，列出支持和反对的观点，然后得出有依据的结论。

Published by TutorHao | Economics Revision Series | aleveler.com

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Oligopoly | 寡头