Monopoly | 垄断

📚 Monopoly | 垄断

In WJEC IGCSE Economics, monopoly refers to a market structure where there is only one seller of a particular good or service, and where entry of new firms into the industry is restricted. The monopolist is therefore the industry, and possesses significant market power to set price and output. Understanding the nature, causes, consequences and possible remedies of monopoly is essential for analysing real‑world markets and government policy.

在 WJEC IGCSE 经济学中，垄断是指某一特定商品或服务只有一个卖家，且新企业进入该行业受到限制的市场结构。垄断企业即代表整个行业，拥有设定价格和产量的重大市场支配力。理解垄断的性质、成因、后果及可能的对策，对于分析现实世界中的市场和政府政策至关重要。

1. Definition and Key Characteristics | 定义与关键特征

A pure monopoly exists when a single firm is the sole supplier of a product without any close substitutes. The firm is a price‑maker, meaning it can influence the market price by adjusting its output. High barriers to entry prevent other firms from entering the market and competing away any abnormal profit.

当一家企业成为某种没有近似替代品的产品的唯一供应商时，就存在纯粹垄断。这家企业是价格制定者，即能够通过调整产量来影响市场价格。较高的进入壁垒阻止了其他企业进入市场并通过竞争消除任何超额利润。

Because the monopolist is the industry, it faces the entire market demand curve, which is downward sloping. This shape tells us that to sell extra units, the monopolist must lower the price on all units sold (in a simple single‑price model). The firm’s average revenue (AR) equals the price, but its marginal revenue (MR) lies below the AR curve; each additional unit sold brings in less revenue than the price at which it is sold because the price reduction applies to all previous units.

由于垄断企业就是整个行业，它面对的是整个市场的需求曲线，该曲线向右下方倾斜。这表明，为了多销售一单位商品，垄断者必须降低所有销售单位的价格（在简单的单一定价模型中）。企业的平均收益 (AR) 等于价格，但其边际收益 (MR) 位于平均收益曲线之下；每多销售一单位带来的收益低于其售价，因为降价同样适用于之前销售的所有单位。

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2. Types of Monopoly | 垄断的类型

In your exam you may be asked to distinguish between different forms of monopoly. A pure monopoly is a theoretical extreme where one firm controls 100% of the market. An actual monopoly is often defined by law when a firm controls at least 25% of the market (the UK legal definition used by the Competition and Markets Authority), though this is technically a dominant position rather than a pure monopoly. A natural monopoly occurs where it is most efficient for a single firm to supply the entire market due to extremely high fixed costs and continuous falling long‑run average cost over the relevant range of output.

考试中可能会要求你区分垄断的不同形式。纯粹垄断是理论上的极端情况，即一家企业掌控 100% 的市场份额。实际垄断通常根据法律定义，当一家企业控制至少 25% 的市场时（英国竞争与市场管理局采用的法律定义），即可视为具有支配地位，尽管这在技术上更接近支配地位而非纯粹垄断。自然垄断发生在由单一企业供应整个市场最为高效的情况下，这是因为极高的固定成本以及在整个相关产出范围内长期平均成本持续下降。

Examples of natural monopolies include water supply networks, railway infrastructure and electricity transmission grids, where duplication of infrastructure would be wasteful and raise average costs sharply.

自然垄断的例子包括供水管网、铁路基础设施和输电网络，重复建设这些基础设施会造成浪费并使平均成本大幅上升。

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3. Barriers to Entry | 进入壁垒

Barriers to entry are obstacles that make it difficult or impossible for new firms to enter a market. They are essential for maintaining a monopoly position. There are several types:

进入壁垒是使新企业难以或无法进入市场的障碍。这些壁垒对于维持垄断地位至关重要。主要分为以下几种类型：

Legal barriers: Patents grant exclusive rights to produce a new invention for a set period. Copyrights and trademarks offer similar protection for creative works and brands. Government licences can limit the number of operators, e.g. in taxi services or broadcasting.

法律壁垒：专利权授予一定时期内独家生产新发明的权利。版权和商标对创作作品和品牌提供类似的保护。政府颁发的许可证可以限制经营者的数量，例如出租车服务或广播业。

Natural barriers: High fixed costs and economies of scale may make it unprofitable for a second firm to enter, creating a natural monopoly. Sunk costs — costs that cannot be recovered if the firm exits — also deter entry.

自然壁垒：高昂的固定成本和规模经济可能使第二家企业进入市场变得无利可图，从而形成自然垄断。沉没成本——企业退出时无法收回的成本——也阻碍进入。

Strategic barriers: An incumbent monopolist may adopt predatory pricing (cutting prices below cost to drive out rivals), build up spare capacity so it can flood the market and lower price if a competitor enters, or create brand loyalty through heavy advertising.

策略壁垒：现有垄断者可能采取掠夺性定价（将价格降至成本以下以排挤对手），建立过剩产能以便在有竞争者进入时充斥市场并压低价格，或通过大量广告建立品牌忠诚度。

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4. Monopolist’s Demand, AR and MR Curves | 垄断者的需求、平均收益和边际收益曲线

In monopoly, the firm’s demand curve is the same as the market demand curve and is downward sloping. Average revenue (AR) at each quantity equals the price. However, marginal revenue (MR) is less than AR for every unit beyond the first, because to sell an extra unit the monopolist must accept a lower price on all units sold. The MR curve is twice as steep as the linear demand (AR) curve. This relationship can be shown as: if demand is given by P = a − bQ, then MR = a − 2bQ.

在垄断市场中，企业的需求曲线与市场需求曲线完全相同，且向右下方倾斜。每个产量上的平均收益 (AR) 等于价格。然而，除首单位外，每一个销售单位的边际收益 (MR) 均低于平均收益，因为为了多销售一单位，垄断者必须接受所有销售单位的价格下降。边际收益曲线比线性需求（平均收益）曲线陡两倍。这种关系可以表示为：若需求为 P = a − bQ，则 MR = a − 2bQ。

Key fact: for a monopolist, AR = Price, but MR < Price

关键事实：对于垄断者，AR = 价格，但 MR < 价格

This has important implications for profit maximisation, because the monopolist will produce where MR = MC, not where price equals MC.

这对利润最大化有重要影响，因为垄断者会在 MR = MC 处进行生产，而非价格等于 MC 处。

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5. Profit Maximisation in Monopoly | 垄断企业的利润最大化

A monopolist will aim to maximise profit by producing the output where marginal cost (MC) equals marginal revenue (MR). The price is then determined by the height of the demand (AR) curve at that quantity. Because the price exceeds MC at this output, the monopolist earns abnormal (supernormal) profit in the short run. Crucially, barriers to entry protect this abnormal profit in the long run too; unlike in perfect competition, the monopolist can continue to earn supernormal profit indefinitely.

垄断企业通过生产边际成本 (MC) 等于边际收益 (MR) 的产量来实现利润最大化。然后，价格由该产量处需求（平均收益）曲线的高度决定。由于在该产量上，价格高于边际成本，垄断者在短期获得超额（超常）利润。关键是，进入壁垒保护了这种超额利润在长期内也得以持续；与完全竞争不同，垄断者可以无限期地继续赚取超常利润。

In a diagram, the area of supernormal profit is shown by the rectangle (AR − AC) × Q at the profit‑maximising output, where AC is average cost.

在图表中，超额利润区域由利润最大化产量下的矩形(AR − AC) × Q 表示，其中 AC 为平均成本。

Monopolists are not guaranteed profit; if average cost lies above demand at all output levels, the firm may make a loss and eventually exit. However, the existence of monopoly power reduces the risk of permanent normal‑profit outcomes.

垄断并不能保证一定能获得利润；如果平均成本在所有产量水平上都高于需求，企业可能会亏损并最终退出。但垄断力量的存在降低了长期只获得正常利润的可能性。

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6. Comparison with Perfect Competition | 与完全竞争的比较

It is a standard WJEC exam requirement to contrast monopoly with perfect competition. Under perfect competition, the equilibrium occurs where P = MC, achieving allocative efficiency. In monopoly, equilibrium occurs at MR = MC, with P > MC, indicating allocative inefficiency — the monopolist produces less and charges a higher price than would occur in a competitive market. Productive efficiency is not guaranteed in either market, but a monopolist has less incentive to minimise costs because of the lack of competitive pressure.

将垄断与完全竞争进行比较是 WJEC 考试的常规要求。在完全竞争下，均衡发生在 P = MC 处，实现了分配效率。在垄断中，均衡发生在 MR = MC 处，且 P > MC，表明存在分配无效率——与竞争性市场相比，垄断者生产更少的产量并收取更高的价格。这两种市场均无法保证生产效率，但由于缺乏竞争压力，垄断者减少成本的动力较弱。

Table comparing key outcomes:

Feature	Perfect Competition	Monopoly
Number of firms	Many	One
Price	Lower	Higher
Output	Higher	Lower
Profit in long run	Normal only	Supernormal possible
Efficiency	Allocatively efficient (P=MC)	Allocatively inefficient (P>MC)

特征对比表：

特征	完全竞争	垄断
企业数量	许多	一家
价格	较低	较高
产量	较高	较低
长期利润	仅正常利润	可能获取超常利润
效率	分配有效率 (P=MC)	分配无效率 (P>MC)

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7. Disadvantages of Monopoly | 垄断的缺点

WJEC candidates must be able to evaluate the costs of monopoly power. The main disadvantages are:

WJEC 考生必须能够评价垄断力量的代价。主要缺点包括：

Higher prices for consumers: The monopolist restricts output to raise price, reducing consumer surplus and transferring some of it to producers as producer surplus. This creates a deadweight loss of welfare to society — the net loss of consumer and producer surplus that is not transferred to anyone.

消费者支付更高价格：垄断者限制产量以提高价格，从而减少了消费者剩余，并将其中一部分转化为生产者剩余。这造成了社会的无谓福利损失——未被转移给任何一方的消费者剩余和生产者剩余的净损失。

Allocative inefficiency: Price exceeds MC, meaning consumers value the good more than the cost of producing an additional unit. Too little is produced from society’s point of view.

分配无效率：价格高于边际成本，意味着消费者对商品的评价高于生产额外一单位的成本。从社会的角度看，产量过少。

Productive inefficiency (X‑inefficiency): Without competitive pressure, monopolists may suffer from organisational slack and higher costs than necessary. Managers may not strive to cut costs or innovate.

生产无效率（X‑非效率）：缺乏竞争压力时，垄断者可能出现组织松懈，成本高于必要水平。管理者可能不会努力降低成本或创新。

Reduced consumer choice and potential for lower quality.

消费者选择减少，并可能导致质量下降。

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8. Possible Advantages of Monopoly | 垄断的可能优点

Despite the textbook critique, monopolies can bring benefits that are often tested in long‑answer questions.

尽管教科书上有所批评，但垄断可以带来一些好处，这些常在长答题中被考查。

Economies of scale: A large monopolist can achieve lower long‑run average costs through technical, purchasing, financial and managerial economies, which may lead to lower prices for consumers than could be offered by smaller fragmented competitors — especially in natural monopoly industries.

规模经济：大型垄断企业可以通过技术、采购、财务和管理上的规模经济降低长期平均成本，从而可能为消费者提供比小型分散竞争者更低的价格——尤其是在自然垄断行业。

Finance for research and development (R&D): Supernormal profits provide internal funds for innovation and technological progress. In industries like pharmaceuticals, the promise of monopoly profits (via patents) encourages firms to spend heavily on R&D, ultimately benefiting consumers with new and better products.

研发资金：超额利润为创新和技术进步提供了内部资金。在制药等行业，垄断利润的预期（通过专利）鼓励企业大量投入研发，最终以新的、更好的产品使消费者受益。

International competitiveness: A domestic monopoly might be large enough to compete effectively in global markets, achieving export success that many small firms could not.

国际竞争力：国内垄断企业可能规模足够大，能够在全球市场上有效竞争，取得众多小企业无法实现的出口成就。

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9. Natural Monopoly and Regulation | 自然垄断与规制

A natural monopoly arises when long‑run average cost (LRAC) falls continuously over the relevant range of output. Splitting the industry into two or more firms would raise total costs and prices. Common examples include water supply, rail infrastructure and electricity transmission. In these cases, direct competition would be inefficient, so government intervention is needed to protect consumers.

当长期平均成本 (LRAC) 在相关产量范围内持续下降时，便产生自然垄断。将行业分割成两家或多家企业将提高总成本和价格。供水、铁路基础设施和输电就是常见的例子。在这些情况下，直接竞争将是低效率的，因此需要政府干预以保护消费者。

Regulation methods include:

规制方法包括：

• Price controls (RPI−X or rate‑of‑return regulation) that limit the price a monopolist can charge to something closer to average cost, while allowing a fair return.
• Quality standards to prevent cost‑cutting that harms service.
• Nationalisation, where the state owns the monopoly and can set prices at marginal cost, although state‑run monopolies may also suffer from inefficiency.

• 价格管控（RPI−X 或回报率管制），将垄断者所能收取的价格限制在接近平均成本的水平，同时允许获得合理回报。
• 质量标准，防止降低服务质量的成本削减。
• 国有化，国家拥有垄断企业，可以将价格定在边际成本水平，尽管国有垄断也可能存在低效率问题。

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10. Government Policy Towards Monopoly | 政府针对垄断的政策

Governments use a range of policies to deal with monopoly power. Competition policy (e.g. the UK Competition and Markets Authority) investigates and prevents anti‑competitive practices such as collusion, abuse of a dominant position, and mergers that would substantially reduce competition. Fines can be imposed, and in extreme cases companies may be broken up.

政府采用一系列政策应对垄断力量。竞争政策（如英国竞争与市场管理局）调查并阻止反竞争行为，如合谋、滥用支配地位以及会大幅减少竞争的合并。可以处以罚款，在极端情况下甚至可以拆分企业。

Direct regulation of natural monopolies, as described above, controls price and quality. Governments may also introduce performance targets and encourage competitive tendering for the right to run a service (franchising), which introduces competition ‘for the market’ rather than ‘in the market’.

对自然垄断的直接规制，如上所述，用于控制价格和质量。政府还可以引入绩效目标，并鼓励通过竞争性招标获得某项服务的运营权（特许经营），这引入了“为市场”而非“在市场中”的竞争。

Trade liberalisation can reduce monopoly power by exposing domestic firms to foreign competition.

贸易自由化可以让国内企业面对外国竞争，从而削弱垄断力量。

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11. Evaluation: Is Monopoly Always Bad? | 评估：垄断总是坏的吗？

When discussing monopoly in a WJEC exam, it is vital to show balance. The harm of monopoly depends on the degree of market power, the height of barriers to entry, the existence of potential competition (contestability), and whether the market is dynamic. A temporary monopoly protected by a patent may be beneficial if it speeds up innovation. A monopoly that faces fierce international competition may behave as if it were in a competitive market. Government regulation can mitigate many of the negative effects, but regulation itself brings costs and may fail (government failure).

在 WJEC 考试中讨论垄断时，表现出平衡的视角至关重要。垄断的危害取决于市场力量的程度、进入壁垒的高低、潜在竞争（可竞争性）的存在与否，以及市场是否具有动态性。受专利保护的暂时性垄断如果能加速创新，则可能是有益的。面临激烈国际竞争的垄断企业的行为可能如同处在竞争市场中一样。政府规制可以减轻许多负面影响，但规制本身也会带来成本，并可能失灵（政府失灵）。

Therefore, a blanket condemnation of monopoly is unjustified; careful case‑by‑case analysis is needed.

因此，一味谴责垄断是不合理的；需要进行具体情况具体分析。

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12. Key Exam Tips for Monopoly | 垄断考点解题技巧

In data response and essay questions, always define monopoly precisely and stress the importance of barriers to entry. Use diagrams to show the profit‑maximising output (MR=MC) and the resulting welfare loss. Compare monopoly with perfect competition to highlight efficiency differences. Bring in real‑world examples, such as local water companies (natural monopoly), tech giants, or patent‑protected pharmaceuticals. Be ready to discuss both costs and benefits, and to evaluate government measures. Use accurate terminology: abnormal profit, allocative efficiency, deadweight loss, X‑inefficiency, and contestability.

在数据回答和论文题中，始终精确地定义垄断，并强调进入壁垒的重要性。使用图表展示利润最大化产量 (MR=MC) 以及由此产生的福利损失。将垄断与完全竞争进行比较，以突出效率差异。引入现实世界中的例子，如地方水务公司（自然垄断）、科技巨头或受专利保护的药企。准备好讨论成本与收益两方面，并评价政府措施。使用准确的术语：超额利润、分配效率、无谓损失、X‑非效率以及可竞争性。

Remember that in WJEC, you may be asked to evaluate the view that monopoly leads to a misallocation of resources, or to discuss whether a monopoly is ever desirable. Support your arguments with clear economic reasoning.

请记住，在 WJEC 考试中，你可能会被要求评价“垄断导致资源错误配置”的观点，或者讨论垄断是否可能有可取之处。请用清晰的经济推理来支持你的论点。

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