Market Failure: WJEC A-Level Economics Key Points | 市场失灵：WJEC A-Level 经济考点精讲

📚 Market Failure: WJEC A-Level Economics Key Points | 市场失灵：WJEC A-Level 经济考点精讲

Market failure is a central topic in WJEC A-Level Economics that examines situations where the free market fails to allocate resources efficiently, leading to a net social welfare loss. This revision guide covers the causes, consequences and policy responses with clear explanations and examples relevant to the WJEC specification.

市场失灵是 WJEC A-Level 经济的核心主题，探讨自由市场无法有效配置资源从而导致社会净福利损失的情况。本复习指南涵盖其原因、后果和政策应对，配以针对 WJEC 大纲的清晰解释和实例。

1. What is Market Failure? | 什么是市场失灵？

Market failure occurs when the price mechanism fails to account for all costs and benefits when providing a good, resulting in a misallocation of resources. In WJEC exams, you need to define it precisely and explain that it leads to allocative inefficiency, where the community’s welfare is not maximised.

市场失灵发生在价格机制无法将提供某种商品时的全部成本与收益纳入考虑，从而导致资源配置不当。在 WJEC 考试中，你需要准确定义它，并解释它会导致配置无效率，即社会福利未能最大化。

In a perfectly competitive market with no externalities, full information and private property rights, the market produces an allocatively efficient outcome. However, whenever one of those conditions is missing, market failure arises. The WJEC specification focuses on specific types: externalities, public goods, information asymmetries, monopoly power, and inequality in income distribution.

在一个没有外部性、信息充分且产权清晰的完全竞争市场中，市场会产生配置有效的结果。然而，一旦这些条件有一项缺失，市场失灵就会出现。WJEC 大纲重点关注的具体类型包括：外部性、公共物品、信息不对称、垄断力量以及收入分配不平等。

The consequence of market failure is a deadweight loss (DWL) – a loss of social surplus that is not gained by anyone. This concept underpins the justification for government intervention throughout the course.

市场失灵的后果是无谓损失 (DWL)——即社会剩余的损失，且无人从中获益。这一概念为整个课程中政府干预的合理性奠定了基础。

2. Negative Externalities in Detail | 负外部性详解

A negative externality is a cost imposed on a third party not involved in the economic transaction. For instance, a factory emitting pollution harms local residents who are not compensated. The market overproduces such goods because producers ignore the external cost, leading to a divergence between private and social costs.

负外部性是强加于未参与经济交易的第三方的成本。例如，工厂排放污染损害了当地居民的健康，却未给予补偿。市场过度生产此类商品，因为生产者忽视了外部成本，导致私人成本与社会成本发生背离。

MSC = MPC + MEC

边际社会成本 (MSC) = 边际私人成本 (MPC) + 边际外部成本 (MEC)

In a free market diagram, the private optimum occurs where MPB = MPC (point A), producing quantity Q_market. But the social optimum is at a lower quantity Q_opt where MSB = MSC (point B). The distance Q_market to Q_opt represents overproduction, and the triangle between the MSC and MSB curves from Q_opt to Q_market is the welfare loss.

在自由市场图中，私人最优出现在 MPB = MPC 处（点 A），产量为 Q_market。但社会最优位于更低产量 Q_opt，满足 MSB = MSC（点 B）。从 Q_market 到 Q_opt 的距离代表过度生产，而在 Q_opt 到 Q_market 之间 MSC 与 MSB 曲线围成的三角形即为福利损失。

Common exam examples include carbon emissions from electricity generation, noise pollution near airports, passive smoking, and overuse of plastic packaging. Remember to label the vertical distance between MSC and MPC as the marginal external cost.

常见考题例子包括发电产生的碳排放、机场附近的噪音污染、被动吸烟以及塑料包装的过度使用。记得在图上将 MSC 与 MPC 的垂直距离标注为边际外部成本。

To correct this,

Published by TutorHao | A-Level Economics Revision Series | aleveler.com

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