Monopoly in A-Level Economics | A-Level 经济：垄断 考点精讲

📚 Monopoly in A-Level Economics | A-Level 经济：垄断 考点精讲

Monopoly is a key market structure studied at A-Level Economics, representing the opposite extreme to perfect competition. In a monopoly, a single firm supplies the entire market, raising important questions about efficiency, consumer welfare, and the need for regulation.

垄断是 A-Level 经济学中研究的一种关键市场结构，代表着与完全竞争相反的极端情况。在垄断中，单一企业供应整个市场，这引发了关于效率、消费者福利以及是否需要监管的重要问题。

1. What is Monopoly? | 什么是垄断？

A pure monopoly exists when a single firm is the sole supplier of a good or service that has no close substitutes. The firm therefore represents the entire industry.

当一家企业是某种没有近似替代品的商品或服务的唯一供应者时，就存在纯粹垄断。因此该企业即代表整个行业。

Because the monopolist faces the whole market demand curve, its demand curve is downward sloping. To sell more output, it must lower the price on all units sold.

由于垄断者面对整个市场的需求曲线，其需求曲线是向下倾斜的。为了销售更多产量，它必须降低所有已售单位的价格。

A key implication is that the monopolist is a price-maker, able to choose the profit-maximising combination of price and output, rather than accepting the market price as in perfect competition.

一个关键含义是垄断者是价格制定者，能够选择利润最大化的价格与产量组合，而非像完全竞争那样接受市场价格。

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2. Key Characteristics | 关键特征

A monopoly is characterised by a single seller dominating the market. This solitary producer has significant market power.

垄断的特征是单一卖方主导市场。这一独家企业拥有显著的市场力量。

There are no close substitutes for the product, meaning consumers lack viable alternatives and must buy from the monopolist or go without.

产品没有近似替代品，这意味着消费者缺乏可行的替代选择，必须从垄断者处购买或者放弃消费。

High barriers to entry prevent other firms from entering the market and competing away supernormal profits.

高进入壁垒阻止其他企业进入市场并瓜分超额利润。

The monopolist can influence price by adjusting its output level, making it a price-maker rather than a price-taker.

垄断者可以通过调整产量水平来影响价格，从而成为价格制定者而非价格接受者。

Imperfect information may exist, and the monopolist might not face the same pressure to minimise costs as firms in competitive markets.

可能存在不完全信息，垄断者可能不会面临竞争市场中企业那种最小化成本的压力。

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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 sustaining monopoly power in the long run.

进入壁垒是使新企业难以或无法进入市场的障碍。它们对于长期维持垄断力量至关重要。

Legal barriers include patents that grant exclusive production rights for a set period, and licenses that restrict entry to certain professions or industries.

法律壁垒包括授予一定时期内独家生产权的专利，以及限制进入特定职业或行业的许可证。

Economies of scale can create a natural monopoly, where a single firm can supply the entire market at a lower average cost than two or more firms.

规模经济可能造成自然垄断，即一家企业能够以比两家或更多企业更低的平均成本供应整个市场。

Control over essential raw materials or distribution channels can also block entry, as seen in the diamond industry historically.

对关键原材料或分销渠道的控制也可能阻止进入，历史上钻石行业就是如此。

High sunk costs and aggressive price-cutting (predatory pricing) by incumbent firms can deter potential entrants.

沉没成本高昂以及现有企业的激进降价（掠夺性定价）可以威慑潜在进入者。

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4. Profit Maximisation | 利润最大化

A monopolist maximises profit by equating marginal revenue (MR) to marginal cost (MC). Hence the profit-maximising output is determined where MR = MC.

垄断者通过使边际收入（MR）等于边际成本（MC）来最大化利润。因此，利润最大化产量在 MR = MC 处确定。

Once the output is chosen, the firm charges the highest possible price by reading up to the demand curve. This price exceeds marginal cost, and supernormal profits can be earned if average cost is below the price.

一旦选择好产量，企业通过向上读取需求曲线来设定可能的最高价格。这一价格超过边际成本，如果平均成本低于价格，则可以获得超额利润。

Because high barriers to entry persist, monopolists may maintain supernormal profits in the long run, unlike perfectly competitive firms where profits are competed away.

由于高进入壁垒持续存在，垄断者可能在长期内保持超额利润，这与完全竞争企业利润被竞争侵蚀的情形不同。

The relationship among price, average revenue and marginal revenue is important: for a linear downward-sloping demand, the MR curve lies twice as steep as the demand curve and may become negative.

价格、平均收入和边际收入之间的关系很重要：对于线性向下倾斜的需求曲线，MR 曲线位于需求曲线下方，斜率是需求曲线的两倍，并且可能变为负值。

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5. Comparison with Perfect Competition | 与完全竞争的对比

Under perfect competition, firms are price-takers and produce where P = MC, resulting in allocative efficiency and a higher output at a lower price.

在完全竞争下，企业是价格接受者，在 P = MC 处生产，从而实现分配效率，产量更高、价格更低。

By contrast, a monopolist restricts output to raise price above marginal cost, creating a deadweight loss to society. Consumers lose surplus that is not fully transferred to the producer.

相比之下，垄断者限制产量以将价格提高到边际成本之上，给社会造成无谓损失。消费者损失了一部分并未完全转移给生产者的剩余。

While a perfectly competitive market achieves both allocative and productive efficiency in the long run, monopoly typically fails on both counts, though it may offer dynamic efficiency through higher profits.

完全竞争市场在长期实现分配效率和生产效率，而垄断通常在这两方面均无法达到，尽管其可能通过更高的利润带来动态效率。

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6. Allocative Inefficiency and Deadweight Loss | 分配无效率与无谓损失

Allocative efficiency occurs when price equals marginal cost (P = MC), meaning that resources are allocated in a way that maximises total welfare. The monopoly equilibrium has P > MC, so output is too low and price too high.

当价格等于边际成本（P = MC）时，实现分配效率，即资源配置使总福利最大化。垄断均衡下 P > MC，因此产量过低而价格过高。

The resulting deadweight loss is a triangle between the demand and marginal cost curves, representing the net loss of consumer and producer surplus that no one gains.

由此产生的无谓损失是需求曲线与边际成本曲线之间的一个三角形，代表了消费者和生产者剩余的净损失，无人从中获益。

This inefficiency is a primary rationale for government intervention, such as price regulation or breaking up monopolies, to bring the market closer to the socially optimal output.

这种无效率是政府干预的主要理由之一，如实施价格监管或分拆垄断企业，以使市场更接近社会最优产量。

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7. Productive and X-inefficiency | 生产效率与 X-非效率

Productive efficiency refers to production at the lowest point on the average cost curve. Monopolists may not have an incentive to produce at the minimum average cost because they are shielded from competition.

生产效率是指在平均成本曲线的最低点进行生产。由于缺乏竞争压力，垄断者可能没有动力在最低平均成本处生产。

X-inefficiency arises when a firm’s costs are higher than necessary due to organisational slack, poor management, or lack of competitive pressure. Monopolies are particularly prone to this, leading to wasteful use of resources.

当企业由于组织松散、管理不善或缺乏竞争压力而导致成本高于必要水平时，出现 X-非效率。垄断企业尤其容易出现这种情况，导致资源浪费。

However, some economists argue that monopolies can achieve dynamic

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