📚 Merit Goods, Demerit Goods and Information Failure | 有益品、有害品与信息失灵
In a free market, the price mechanism usually allocates resources efficiently when consumers and producers have perfect information and act rationally. However, many goods and services are consumed at levels that differ from the social optimum because of information problems and external effects. This article explains the concepts of merit goods, demerit goods and information failure, and evaluates possible government responses.
在自由市场中，当消费者和生产者拥有完全信息并理性行动时，价格机制通常能够有效配置资源。然而，许多商品和服务的消费水平因信息问题和外部效应而偏离社会最优水平。本文解释有益品、有害品和信息失灵的概念，并评价政府可能采取的应对措施。
1. Understanding Market Failure | 理解市场失灵
Market failure occurs when the free market, left to its own devices, fails to allocate resources in a way that maximises social welfare. In perfect competition, the equilibrium quantity is where marginal private benefit equals marginal private cost. This outcome is socially efficient only if private benefits and costs reflect all social benefits and costs, and if buyers and sellers have full information. In reality, these conditions rarely hold, especially for goods such as education, healthcare, tobacco and alcohol.
当自由市场自行运行时，如果无法以实现社会福利最大化的方式配置资源，就会发生市场失灵。在完全竞争中，均衡数量位于边际私人收益等于边际私人成本之处。只有当私人收益和成本反映所有社会收益和成本、并且买卖双方拥有完全信息时，这一结果才具有社会效率。现实中，这些条件很少成立，尤其是教育、医疗、烟草和酒精等商品。
2. What Are Merit Goods? | 什么是有益品？
A merit good is a good or service that society believes is beneficial for individuals, but which tends to be under-consumed in a free market. Education, healthcare, vaccinations, public libraries and preventive medical check-ups are common examples. The under-consumption arises because individuals do not fully appreciate the private benefits, or because they ignore the positive externalities that their consumption creates for others.
有益品是指社会认为对个人有益、但在自由市场中往往被消费不足的商品或服务。教育、医疗、疫苗接种、公共图书馆和预防性体检是常见例子。消费不足的原因是个人没有充分认识到私人收益，或者忽视了其消费给他人带来的正外部性。
Merit goods have two key features. First, they generate positive externalities, so the marginal social benefit (MSB) exceeds the marginal private benefit (MPB). Second, consumers suffer from imperfect information: they may underestimate the long-term private benefits. For example, a teenager may not fully value the future income gains from staying in education.
有益品有两个关键特征。第一，它们产生正外部性，因此边际社会收益（MSB）大于边际私人收益（MPB）。第二，消费者面临不完全信息：他们可能低估长期私人收益。例如，青少年可能没有充分认识到继续接受教育带来的未来收入增长。
3. What Are Demerit Goods? | 什么是有害品？
A demerit good is a good or service that society considers harmful to individuals, but which tends to be over-consumed in a free market. Tobacco, alcoholic drinks, recreational drugs, gambling and sugary drinks are typical examples. Over-consumption occurs because consumers overestimate the immediate private benefits, underestimate the long-term private costs, and ignore the negative externalities imposed on third parties.
有害品是指社会认为对个人有害、但在自由市场中往往被过度消费的商品或服务。烟草、酒精饮料、娱乐性药物、赌博和含糖饮料是典型例子。过度消费的原因是消费者高估了即期私人收益，低估了长期私人成本，并忽视了强加给第三方的负外部性。
Demerit goods are associated with negative externalities, so the marginal social cost (MSC) exceeds the marginal private cost (MPC). In addition, consumers often lack accurate information about health risks or addiction probabilities, leading them to make decisions that reduce their own welfare in the long run.
有害品与负外部性相关，因此边际社会成本（MSC）大于边际私人成本（MPC）。此外，消费者往往缺乏关于健康风险或成瘾概率的准确信息，导致他们做出长期降低自身福利的决策。
4. Information Failure as a Root Cause | 信息失灵作为根本原因
Information failure occurs when one or more parties in a transaction do not have full, accurate or timely information needed to make a rational decision. In the case of merit goods, people may not know the true private benefits; in the case of demerit goods, they may not know the true private costs. Advertising, peer pressure, cognitive biases and myopia can all worsen information failure.
信息失灵是指交易中的一方或多方没有做出理性决策所需的完整、准确或及时的信息。就有益品而言，人们可能不了解真正的私人收益；就有害品而言，他们可能不了解真正的私人成本。广告、同伴压力、认知偏差和短视都会加剧信息失灵。
There are two main types of information problems: imperfect information and asymmetric information. Imperfect information means a buyer or seller lacks knowledge about a product’s quality, risks or benefits. Asymmetric information means one side knows more than the other, as in the used-car market. For merit and demerit goods, imperfect information is usually more relevant because consumers misjudge long-term consequences.
信息问题主要有两类：不完全信息和不对称信息。不完全信息是指买方或卖方缺乏关于产品质量、风险或收益的知识。不对称信息是指一方比另一方知道得更多，例如二手车市场。对于有益品和有害品，不完全信息通常更为相关，因为消费者误判了长期后果。
5. Positive Externalities and Under-Consumption of Merit Goods | 正外部性与有益品消费不足
The market equilibrium for a merit good is determined by the intersection of the demand curve (based on marginal private benefit) and the supply curve (based on marginal private cost). Because consumers undervalue the good, the marginal private benefit is below the marginal social benefit. As a result, the free-market quantity Qₘ is smaller than the socially optimal quantity Qₛ, creating a deadweight welfare loss.
有益品的市场均衡由需求曲线（基于边际私人收益）和供给曲线（基于边际私人成本）的交点决定。由于消费者低估该商品的价值，边际私人收益低于边际社会收益。因此，自由市场数量 Qₘ 小于社会最优数量 Qₛ，造成无谓福利损失。
For example, when a person is vaccinated, they gain personal protection, but they also reduce the risk of disease transmission to others. If individuals only consider their own protection, they may decide not to be vaccinated, even though society would benefit from higher vaccination coverage. This under-consumption can lead to outbreaks and higher public health costs.
例如，当一个人接种疫苗时，他们获得个人保护，但也降低了疾病传播给他人的风险。如果个人只考虑自身保护，他们可能决定不接种疫苗，尽管社会会从更高的疫苗接种覆盖率中受益。这种消费不足可能导致疫情暴发和更高的公共卫生成本。
6. Negative Externalities and Over-Consumption of Demerit Goods | 负外部性与有害品过度消费
For a demerit good, the market equilibrium is based on private costs and benefits, but the true social cost is higher because of external costs such as second-hand smoke, drink-driving accidents, strain on public healthcare and reduced workplace productivity. The marginal social cost curve lies above the marginal private cost curve, so the market quantity Qₘ exceeds the social optimum Qₛ.
对于有害品，市场均衡基于私人成本和收益，但由于二手烟、酒后驾驶事故、公共医疗压力和劳动生产率下降等外部成本，真实的社会成本更高。边际社会成本曲线位于边际私人成本曲线上方，因此市场数量 Qₘ 超过社会最优数量 Qₛ。
In addition to external costs, consumers of demerit goods often suffer from internal costs they underestimate, such as future illness, addiction and financial hardship. If they had full information, their private demand would be lower. Information failure therefore causes both private and social over-consumption.
除了外部成本，有害品的消费者往往还要承担他们低估的内部成本，例如未来的疾病、成瘾和财务困难。如果他们拥有完全信息，其私人需求会更低。因此，信息失灵导致私人和社会两方面的过度消费。
7. Consequences of Information Failure | 信息失灵的后果
Information failure in the markets for merit and demerit goods has wide-ranging consequences. Resources are misallocated: too few resources flow to education and preventive healthcare, while too many resources flow to tobacco, alcohol and gambling. This reduces overall economic welfare and can widen health and income inequalities.
有益品和有害品市场中的信息失灵会产生广泛后果。资源被错误配置：流向教育和预防性医疗的资源太少，而流向烟草、酒精和赌博的资源太多。这降低了整体经济福利，并可能扩大健康和收入不平等。
There are also long-term fiscal consequences. Under-consumption of merit goods may lead to a less skilled workforce and lower productivity growth. Over-consumption of demerit goods increases public spending on treating preventable diseases, paying disability benefits and dealing with crime. These costs are borne by taxpayers, including those who made more informed choices.
信息失灵还会带来长期财政后果。有益品消费不足可能导致劳动力技能降低和生产率增长放缓。有害品过度消费增加了用于治疗可预防疾病、支付残疾福利和处理犯罪的公共支出。这些成本由纳税人承担，包括那些做出更明智选择的人。
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