📚 Contestable Markets | 可竞争市场
In traditional market structure analysis, the number of firms and the height of barriers to entry determine the degree of competition. However, the theory of contestable markets shifts the focus from actual competition to potential competition. A market is said to be perfectly contestable when entry and exit are completely free and costless, meaning that incumbent firms are constantly disciplined by the threat of new entrants. Even a monopoly could be forced to behave as if it were in a perfectly competitive market if it faces the credible threat of hit-and-run entry. This topic is central to A-Level Economics and offers a powerful framework for evaluating deregulation and competition policy.
在传统的市场结构分析中，企业的数量和进入壁垒的高度决定了竞争程度。然而，可竞争市场理论将焦点从实际竞争转向了潜在竞争。当一个市场的进入和退出完全自由且无成本时，我们说它是完全可竞争的，这意味着现有企业会时刻受到新进入者威胁的约束。即便是垄断者，如果面临可信的‘打了就跑’式进入威胁，也可能被迫像在完全竞争市场中一样行事。这个主题是A-Level经济学的核心内容，为评估放松管制和竞争政策提供了一个强有力的框架。
1. What is a Contestable Market? | 什么是可竞争市场？
The concept of contestable markets was developed by William Baumol, John Panzar and Robert Willig in the 1980s. A contestable market is one where the number of incumbent firms does not determine behaviour; rather, the ease with which new firms can enter and exit the industry decides prices and output. In a perfectly contestable market, there are no barriers to entry or exit, and all firms, both existing and potential, have access to the same technology. The crucial result is that the market will deliver competitive outcomes regardless of its concentration, as long as the threat of entry is genuine.
可竞争市场这一概念由威廉·鲍莫尔、约翰·潘泽和罗伯特·威利格在20世纪80年代提出。在一个可竞争市场中，现有企业的数量并不决定其行为方式；相反，新企业进入和退出的难易程度决定了价格和产量。在一个完全可竞争的市场中，不存在进入或退出壁垒，并且所有企业，无论是现有的还是潜在的，都可以获得相同的技术。其关键结论是，只要进入威胁是真实的，无论市场集中度如何，它都能产生竞争性结果。
It is essential to understand that contestability is a matter of degree. Few real-world markets are perfectly contestable, but many display a high degree of contestability. The theory is especially useful for analysing industries with few firms, such as airlines on a particular route, or digital platforms, where the absence of sunk costs makes it easy for new competitors to challenge incumbents.
必须理解，可竞争性是一个程度问题。现实世界中很少有市场是完全可竞争的，但许多市场都表现出了高度的可竞争性。这一理论对于分析只有少数企业的行业尤为有用，例如特定航线的航空业或数字平台，在这些领域，由于几乎没有沉没成本，新竞争者很容易挑战现有企业。
2. Key Characteristics of Contestable Markets | 可竞争市场的关键特征
A perfectly contestable market rests on several strict assumptions. First, there must be no barriers to entry or exit — no legal restrictions, no brand loyalty that cannot be overcome, and no exclusive control over essential inputs. Second, all firms, incumbents and potential entrants alike, must have access to identical production techniques. Third, there must be no sunk costs: any capital investment must be fully recoverable if a firm decides to leave the market. Fourth, there is a sufficient number of potential entrants willing to spring into action whenever profitable opportunities arise. Finally, incumbents cannot instantly reduce prices in response to entry; otherwise the threat would not be credible.
一个完全可竞争市场建立在几个严格的假设之上。第一，必须不存在进入或退出壁垒——没有法律限制，没有无法克服的品牌忠诚，没有对关键投入品的排他性控制。第二，所有企业，无论是现有企业还是潜在进入者，都必须能够获得相同的生产技术。第三，必须没有沉没成本：任何资本投资在企业决定退出市场时都必须能够完全收回。第四，必须有足够多的潜在进入者，愿意在有利可图的机会出现时立刻采取行动。最后，现有企业不能在新进入者出现时立即降价；否则威胁就不具有可信性。
The absence of sunk costs is arguably the most important condition. If a newcomer can enter the industry, hire the necessary equipment, and leave without losing any unrecoverable outlays, then the market offers a level playing field. In such an environment, an incumbent earning supernormal profits would immediately attract entry; after the new firm captures some of the profit, it can exit costlessly, and the process repeats until only normal profit remains.
沉没成本的缺乏可以说是最重要的条件。如果新进入者可以进入行业，租用必要的设备，并在不损失任何不可收回支出的情况下退出，那么这个市场就提供了一个公平的竞争环境。在这样的环境中，赚取超额利润的现有企业会立即吸引进入者；当新企业获取部分利润后，它可以无成本地退出，这个过程会不断重复，直到只剩下正常利润为止。
3. The Role of Sunk Costs | 沉没成本的作用
Sunk costs are costs that have already been incurred and cannot be recovered. In the context of contestable markets, they act as the main barrier to exit — and therefore to entry. If a firm must invest heavily in specialised machinery that has no resale value, it cannot leave the market without making a loss. Knowing this, a potential entrant will be reluctant to enter in the first place, even if the incumbent is currently charging a high price.
沉没成本是指已经发生且无法收回的成本。在可竞争市场的语境下，它们构成了主要的退出壁垒——因而也是进入壁垒。如果一家企业必须大量投资于没有转售价值的专用机器，那么它就无法在不蒙受损失的情况下退出市场。认识到这一点后，潜在进入者一开始就不愿意进入，即使现有企业目前正在收取高价。
Consequently, high sunk costs insulate incumbents from potential competition and allow them to sustain supernormal profits. Conversely, when sunk costs are low — for example, in an industry where office space can be rented on short-term leases and software is cloud-based — the market becomes more contestable. The threat of hit-and-run entry disciplines the behaviour of existing firms, forcing them to keep prices close to average costs.
因此，高昂的沉没成本使现有企业免受潜在竞争的威胁，使它们得以维持超额利润。相反，当沉没成本很低时——例如，在一个可以短期租赁办公空间且软件部署在云端的行业里——市场的可竞争性就会变强。‘打了就跑’式进入的威胁会约束现有企业的行为，迫使它们将价格保持在接近平均成本的水平。
For A-Level analysis, it is helpful to list some industries with low sunk costs: online retail, food delivery platforms, intercity coach services, and certain financial services. In each case, a new competitor can enter with a modest upfront investment and exit without substantial losses, making these markets highly contestable in practice.
对于A-Level分析，列举一些沉没成本较低的行业会很有帮助：在线零售、食品配送平台、城际长途大巴服务和某些金融服务。在每种情况下，新竞争者都可以以适度的前期投资进入市场，并能在不遭受重大损失的情况下退出，这使得这些市场在实践中具有很强的可竞争性。
4. Hit-and-Run Competition | ‘打了就跑’式竞争
The most distinctive prediction of contestable market theory is hit-and-run entry. Suppose an incumbent firm is charging a price above average cost, earning supernormal profit. A potential entrant can quickly set up production, undercut the incumbent’s price by a small margin, grab a share of the market, make a temporary profit, and then exit before the incumbent retaliates. Because exit is costless, the entrant risks only the opportunity cost of its time.
可竞争市场理论最独特的预测就是‘打了就跑’式进入。假设一家现有企业的定价高于平均成本，正在赚取超额利润。潜在进入者可以迅速建立生产设施，以比现有企业略低的价格切入，抢占一部分市场份额，获得临时利润，然后在现有企业反击之前退出。由于退出是无成本的，进入者所冒的风险仅仅是其时间的机会成本。
In reality, hit-and-run competition is rare in its pure form because few markets have zero sunk costs and zero response time from incumbents. However, the concept remains powerful as a thought experiment: it shows that even a monopoly cannot exploit consumers if it is constantly vulnerable to lightning-fast entry. The mere threat of such competition can produce an efficient outcome.
在现实中，纯粹的‘打了就跑’式竞争很少见，因为很少市场的沉没成本为零且现有企业的反应时间为零。然而，作为一个思想实验，这一概念仍然很有力量：它表明，即便是垄断者，如果始终容易受到闪电般快速的进入的冲击，也无法剥削消费者。仅仅这种竞争的威胁就能产生有效率的结果。
5. Behaviour of Firms in Contestable Markets | 可竞争市场中企业的行为
In a perfectly contestable market, the equilibrium must satisfy two conditions. First, the price cannot exceed average cost; otherwise entry would occur. Second, the price cannot fall below average cost for long, because firms would exit. Therefore, in long-run equilibrium, price equals average cost P = AC. Furthermore, because there is no waste, firms must operate at the minimum efficient scale to avoid being undercut by leaner entrants. This implies that production is both productively efficient and allocatively efficient, even if the industry is dominated by only one or two firms.
在一个完全可竞争的市场中，均衡必须满足两个条件。第一，价格不能超过平均成本；否则就会发生进入。第二，价格长期内不能低于平均成本，因为企业会退出。因此，在长期均衡中，价格等于平均成本 P = AC。此外，由于不存在浪费，企业必须在最小有效规模上运营，以免被更精简的进入者抢走生意。这意味着生产既具有生产效率，又具有配置效率，即使该行业仅由一两家企业主导。
P = AC = MC
The above equation captures the ideal: market price simultaneously equals average cost and marginal cost. This is the same outcome that would emerge under perfect competition, but it arises here solely from the threat of entry rather than from the presence of a large number of small firms. The crucial policy insight is that regulating the number of firms is less important than ensuring that entry and exit remain open.
上述方程式概括了理想状态：市场价格同时等于平均成本和边际成本。这与完全竞争下的结果相同，但在这里，这一结果的产生完全源于进入威胁，而不是因为存在大量小型企业。关键的政策洞见是，监管企业数量不如确保进入和退出渠道保持畅通来得重要。
6. Comparison with Perfect Competition | 与完全竞争的比较
Superficially, contestable market theory seems very similar to perfect competition: both predict zero supernormal profit in the long run, and both lead to productive and allocative efficiency. However, the mechanisms are completely different. Perfect competition relies on a large number of price-taking firms, homogeneous products, and perfect information among consumers. Contestability, by contrast, can deliver the same outcome with only one firm, provided that entry is entirely free and costless.
从表面上看，可竞争市场理论与完全竞争似乎非常相似：两者都预测长期中的超额利润为零，并且都导致生产效率和配置效率。然而，其机制完全不同。完全竞争依赖于大量的价格接受企业、同质产品和消费者信息完全。而可竞争性理论则可以在只有一家企业的情况下实现相同的结果，只要进入是完全自由和无成本的。
The table below summarises the key distinctions.
下表概括了主要区别。
| Feature | Perfect Competition | Contestable Market |
|---|---|---|
| Number of firms | Very many small firms | Can be one or a few |
| Barriers to entry | None | None (especially no sunk costs) |
| Degree of rivalry | Actual competition among many | Potential competition = discipline |
| Long-run profit | Normal profit only | Normal profit only (by threat) |
| Efficiency outcome | P = MC = min AC | P = AC = MC (when perfectly contestable) |
For an exam answer, the examiner will look for the ability to explain that while the predictions may look similar, contestability does not require a fragmented market structure. This nuance helps explain why industries with a few large players, such as low-cost airlines, can still deliver low fares and constant cost-cutting.
在考试作答中，考官希望看到考生能够解释，虽然预测可能看起来很相似，但可竞争性并不要求市场结构碎片化。这种细微差别有助于解释为什么像低成本航空公司这样只有少数大企业参与的行业，仍然能够提供低价机票并持续削减成本。
7. Efficiency in Contestable Markets | 可竞争市场的效率
A perfectly contestable market achieves both productive efficiency and allocative efficiency. Productive efficiency means that goods are produced at the lowest possible average cost; in contestable markets, any firm that fails to minimise costs would be undercut by a more efficient entrant. Allocative efficiency requires that price equals marginal cost (P = MC), ensuring that resources flow to their most valued uses. The threat of entry pushes price down to the level of marginal cost, so consumer surplus is maximised.
一个完全可竞争的市场同时实现了生产效率和配置效率。生产效率意味着商品以尽可能最低的平均成本生产；在可竞争市场中，任何未能将成本最小化的企业都会被效率更高的进入者抢走生意。配置效率则要求价格等于边际成本（P = MC），从而确保资源流向其最有价值的用途。进入威胁将价格压低至边际成本水平，因此消费者剩余得以最大化。
However, dynamic efficiency — innovation and technological progress — may be weaker in a perfectly contestable market than in a monopoly protected by patents. If every innovation can be instantly imitated by a hit-and-run entrant, the incumbent has little incentive to invest in R&D. Thus a trade-off may exist between static efficiency (lower prices today) and dynamic efficiency (better products tomorrow). This is a key evaluation point for high-band essays.
然而，在完全可竞争的市场中，动态效率——即创新和技术进步——可能弱于受专利保护的垄断市场。如果每一项创新都能被‘打了就跑’的进入者立刻模仿，那么现有企业就几乎没有动力投资研发。因此，在静态效率（即今天的低价格）和动态效率（即明天更好的产品）之间可能存在一个权衡。这是高分论文的一个关键评估点。
8. Real-World Examples of Contestable Markets | 可竞争市场的现实例子
Few markets are perfectly contestable, but several come close. The low-cost airline industry is a classic example. An airline can enter a new route by leasing aircraft and hiring staff on short-term contracts. If the route proves unprofitable, it can redeploy assets elsewhere with little loss. The constant threat of a new budget airline entering a route keeps incumbents’ fares low, even on routes with only one or two carriers.
几乎没有市场是完全可竞争的，但有几个市场很接近。低成本航空业就是一个经典例子。一家航空公司可以通过租赁飞机和签订短期合同雇佣员工来进入一条新航线。如果这条航线最终无利可图，它可以将资产重新部署到其他地方，损失很小。新的廉价航空公司随时可能进入某条航线的持续威胁，使得现有企业的票价保持低位，即使这条航线上只有一两家承运人。
The online retail sector is another example. With a small investment in a website, inventory can be sourced through dropshipping, and exit involves little more than switching off the platform. Similarly, food delivery apps face constant potential entry from rivals that can quickly roll out a similar interface and contract with freelance drivers. In each case, the low level of sunk costs keeps the incumbents alert.
在线零售业是另一个例子。只需对网站进行少量投资，就可以通过代发货模式获取库存，而退出时只需关闭平台即可。类似地，食品配送应用也持续面临来自对手的潜在进入，这些对手可以迅速推出类似的界面并与自由职业司机签约。在每种情况下，低水平的沉没成本都使现有企业保持警觉。
The banking sector, particularly in digital-only banking, demonstrates how regulatory changes can increase contestability. The UK’s ‘open banking’ initiative lowered switching costs for consumers and reduced sunk costs for new fintech entrants, making the market more contestable and prompting established banks to improve their digital services and fee structures.
银行业，尤其是纯数字银行业，展示了监管变革如何提高可竞争性。英国的‘开放银行’计划降低了消费者的转换成本，并减少了新金融科技进入者的沉没成本，从而使市场更具可竞争性，并促使老牌银行改善其数字服务和收费结构。
9. Policy Implications: Deregulation and Competition | 政策含义：放松管制与竞争
The contestable market framework has profoundly influenced competition policy and deregulation. Governments once believed that natural monopolies, such as utilities and railways, had to be operated by state-owned or heavily regulated private firms, because a single set of infrastructure was so expensive to duplicate. Contestability theory suggested an alternative: if the government can ensure that the infrastructure is accessible to all potential users on equal terms — through an open-access regime — then the market for services running over that infrastructure can become contestable.
可竞争市场框架深刻地影响了竞争政策和放松管制。政府曾一度认为，像公用事业和铁路这样的自然垄断行业必须由国有企业或受到严格监管的私营企业经营，因为复制一整套基础设施的成本过于高昂。可竞争性理论提供了一种替代方案：如果政府能够确保所有潜在用户以平等的条件使用该基础设施——通过开放接入制度——那么运行在该基础设施之上的服务市场就可以变得具有可竞争性。
For example, in the UK, the electricity generation market was opened to new entrants while the transmission grid remained a regulated monopoly. As a result, consumers could choose their electricity supplier even though the physical wires were still owned by a single entity. Similar logic applies to rail services: different train operators can compete on the same track, provided the track authority charges fair access fees. In these cases, it is not the number of infrastructure owners that matters, but the openness of the network.
例如，在英国，发电市场放开了新进入者，而输电网络仍然保持着受监管的垄断地位。结果，消费者可以选择自己的电力供应商，尽管实体电线仍然由单一实体拥有。类似的逻辑也适用于铁路服务：只要轨道管理机构收取公平的接入费，不同的火车营运商就可以在同一条轨道上竞争。在这些案例中，重要的不是基础设施所有者的数量，而是网络的开放性。
Regulators such as the Competition and Markets Authority (CMA) now pay close attention to the height of barriers to entry and the level of sunk costs when assessing mergers. Even if a merger reduces the number of firms, it may not substantially lessen competition if the market remains highly contestable. This represents a significant shift from earlier thinking that focused narrowly on market concentration ratios.
在评估并购时，英国竞争与市场管理局（CMA）等监管机构现在高度关注进入壁垒的高度和沉没成本的水平。即使一起并购减少了企业数量，如果市场仍然保持高度的可竞争性，它也可能不会显著削弱竞争。这标志着与早期狭隘地关注市场集中度比率的思维方式相比，已经发生了重大转变。
10. Criticisms and Limitations of Contestability Theory | 对可竞争性理论的批评与局限
Despite its elegance, contestability theory has been criticised for being unrealistic. In most industries, some sunk costs are inevitable: advertising to establish brand recognition, training specialised staff, and acquiring licences all involve costs that cannot be fully recovered. Furthermore, incumbents can often adjust prices quickly, destroying the opportunity for hit-and-run entrants to earn a temporary profit. Loyalty programmes, long-term contracts, and aggressive price matching guarantees can also deter potential competitors.
尽管可竞争性理论很精巧，但因不切实际而受到批评。在大多数行业中，一些沉没成本是不可避免的：为建立品牌知名度而投放广告、培训专业化员工以及获取许可证，都涉及无法完全收回的成本。此外，现有企业往往可以迅速调整价格，从而摧毁‘打了就跑’式进入者赚取临时利润的机会。忠诚度计划、长期合同和激进的‘保证价格匹配’策略也能威慑潜在竞争者。
Another criticism is that the theory places too much weight on static efficiency and ignores the benefits of scale and scope. A single large firm may be able to achieve such low average costs that it can offer lower prices than a host of smaller competitors, while still earning a normal profit. In such a natural monopoly situation, the threat of entry may well be empty because no entrant could match the incumbent’s cost advantage. Contestability thus offers no guarantee of efficiency when economies of scale are significant.
另一个批评是，该理论过于重视静态效率，而忽视了规模经济和范围经济带来的好处。一家大型企业可能能够实现极低的平均成本，从而在仍赚取正常利润的同时，提供比众多小型竞争者更低的价格。在这种自然垄断的情况下，进入威胁很可能是空洞的，因为没有进入者能匹敌现有企业的成本优势。因此，当规模经济显著时，可竞争性并不能保证效率。
Finally, asymmetric information between incumbents and potential entrants can undermine contestability. Incumbents often possess proprietary data on customer behaviour that allows them to spot trends and react more quickly than an outsider. This informational barrier acts as a sunk cost that deters entry even when physical capital costs are negligible.
最后，现有企业与潜在进入者之间的信息不对称会削弱可竞争性。现有企业通常拥有关于客户行为的专有数据，这使它们能够发现趋势并比局外人更快做出反应。这种信息壁垒构成了一种沉没成本，即使实物资本成本可忽略不计，它也会阻止新企业的进入。
11. Contestability and Market Outcomes: A Summary Diagram | 可竞争性与市场结果：总结图示
To consolidate learning, consider the following simplified causal chain.
为巩固所学，请看下面的简化因果链。
Low sunk costs → Easy entry and exit → Credible threat of hit-and-run entry → Incumbents set P = AC to deter entry → Allocative and productive efficiency → Consumer welfare maximised
低沉没成本 → 容易进入和退出 → 可信的‘打了就跑’式进入威胁 → 现有企业设定P = AC以阻止进入 → 配置效率与生产效率 → 消费者福利最大化
This diagrammatic sequence underlines why policymakers focus on removing sunk costs rather than simply breaking up large firms. A concentrated market that is highly contestable may deliver better outcomes than a fragmented market with high entry barriers. Students should use this insight to critically evaluate statements such as ‘a monopoly always harms consumers’.
这一图示序列强调了为什么政策制定者专注于消除沉没成本，而不是简单地拆分大企业。一个高度可竞争且集中的市场，可能比一个存在高进入壁垒的碎片化市场产生更好的结果。学生应运用这一见解来批判性地评估诸如‘垄断总是损害消费者’之类的论断。
12. Exam Tips for Contestable Markets | 关于可竞争市场的考试技巧
When writing an A-Level essay on contestable markets, always define the concept precisely and distinguish it from perfect competition. Use at least one real-world example to illustrate low sunk costs, such as low-cost airlines or online retail. In the evaluation, acknowledge the limitations: real-world sunk costs, strategic barriers, and the possible trade-off with dynamic efficiency. A high-level answer might argue that while perfect contestability is a theoretical benchmark, the threat of entry remains a powerful force that governments can strengthen through pro-competition regulation.
在撰写关于可竞争市场的A-Level论文时，始终要精准定义这一概念，并将其与完全竞争区分开来。至少要使用一个现实世界的例子来说明低沉没成本，例如低成本航空公司或在线零售。在评估部分，要承认其局限性：现实中的沉没成本、策略性壁垒以及与动态效率之间可能存在的权衡。一份高水平的答案可能会指出，尽管完全可竞争性是一个理论基准，但进入威胁仍然是一种强大的力量，政府可以通过有利于竞争的监管来加强它。
Diagrams are not mandatory in all exam boards for this topic, but a simple cost-revenue diagram showing a single firm earning zero supernormal profit at P = AC can support the analysis. Remember to label the axes — price/cost and quantity — and indicate the break-even point clearly. Whenever you mention efficiency, specify whether you are referring to productive, allocative or dynamic efficiency.
并非所有考试局都要求为这一主题画图，但一幅简单的成本-收益图，显示单一企业在 P = AC 处赚取零超额利润，可以为分析提供支持。记得标注坐标轴——价格/成本和数量——并清晰地标出盈亏平衡点。每当提到效率时，要明确你指的是生产效率、配置效率还是动态效率。
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