📚 AP Microeconomics Core Vocabulary Review | AP微观经济核心词汇梳理
Mastering AP Microeconomics begins with a solid understanding of its core vocabulary. These terms are not just definitions to memorise; they are the analytical tools needed to interpret economic models, solve problems, and excel on the exam. This article provides a comprehensive bilingual review of the most essential microeconomic concepts, pairing English explanations with their Chinese equivalents to deepen comprehension.
掌握 AP 微观经济学始于对其核心词汇的扎实理解。这些术语不单是要死记硬背的定义，更是解释经济模型、解决问题和考取高分所需的分析工具。本文提供最核心微观概念的中英双语梳理，将英文解释与中文对照配对，以加深理解。
1. Scarcity and Choice | 稀缺与选择
Scarcity is the fundamental economic problem that arises because resources are limited while human wants are unlimited. It forces individuals, firms, and governments to make choices about how to allocate resources efficiently. Every decision involves a trade-off, meaning that to obtain more of one thing, society must give up some of another.
稀缺性是经济学的基本问题，源于资源有限而人类欲望无限。它迫使个人、企业和政府就如何有效配置资源做出选择。每个决定都涉及权衡，意味着为了获得更多某种东西，社会必须放弃一些其他东西。
Choice is the act of selecting among alternatives. Because of scarcity, economic agents cannot have everything they desire and must prioritise their needs. The production possibilities curve (PPC) illustrates these choices by showing the maximum combinations of two goods an economy can produce with its existing resources and technology.
选择是在不同选项之间进行挑选的行为。由于稀缺性，经济主体不可能拥有想要的一切，必须对需求进行排序。生产可能性曲线（PPC）通过展示一个经济体在现有资源和技术下所能生产的两种商品的最大组合，来说明这些选择。
2. Opportunity Cost | 机会成本
Opportunity cost is the value of the next best alternative foregone when a decision is made. It is not simply the monetary expense but includes all benefits you could have received by taking the next best action. For example, if a student spends an hour studying economics instead of working a part-time job, the opportunity cost is the wage they would have earned.
机会成本是做出某个决定时所放弃的次优选择的价值。它不仅仅是金钱支出，还包括采取次优行动本可获得的全部收益。例如，若一名学生花一小时学习经济学而不是做兼职，机会成本就是他们本可赚到的工资。
Both explicit costs (direct out-of-pocket payments) and implicit costs (foregone benefits like time or owned resources) make up total opportunity cost. Rational decision-making requires comparing the incremental benefits of a choice to its full opportunity cost.
显性成本（直接的自付支出）和隐性成本（放弃的收益，如时间或自有资源）共同构成总机会成本。理性决策要求将选择的增量收益与其全部机会成本进行比较。
3. Marginal Analysis | 边际分析
Marginal analysis involves comparing the additional benefits of an activity to the additional costs. The key rule is to continue an activity as long as the marginal benefit (MB) exceeds the marginal cost (MC). Optimal decisions occur where MB = MC, maximising net total benefit.
边际分析法是比较一项活动的额外收益与额外成本。关键规则是只要边际收益（MB）大于边际成本（MC），就继续该活动。最优决策发生在 MB = MC 时，此时净总收益最大化。
For a firm, marginal revenue (MR) is the change in total revenue from selling one more unit, while marginal cost is the change in total cost from producing one more unit. Profit maximisation requires producing where MR = MC, as long as price covers average variable cost.
对企业而言，边际收益（MR）是多销售一单位产品带来的总收益变化，而边际成本是多生产一单位带来的总成本变化。利润最大化要求在 MR = MC 处生产，只要价格能覆盖平均可变成本。
4. Law of Demand and Supply | 需求与供给定律
The law of demand states that, ceteris paribus, as the price of a good falls, the quantity demanded rises, and vice versa. This inverse relationship is captured by a downward-sloping demand curve. The law of supply states that as price rises, quantity supplied increases, resulting in an upward-sloping supply curve.
需求定律指出，在其他条件不变的情况下，商品价格下降时，需求量上升，反之亦然。这种反向关系表现为向下倾斜的需求曲线。供给定律指出，价格上升时，供给量增加，形成向上倾斜的供给曲线。
Market equilibrium occurs at the price where quantity demanded equals quantity supplied. At this intersection, there is no tendency for change. If price is above equilibrium, a surplus occurs; if below, a shortage arises, and market forces push price back toward equilibrium.
市场均衡发生在需求量与供给量相等的价格处。在这个交点，没有变化的趋势。如果价格高于均衡，就会出现过剩；如果低于均衡，则出现短缺，市场力量会推动价格回归均衡。
5. Price Elasticity of Demand | 需求价格弹性
Price elasticity of demand (PED) measures how responsive quantity demanded is to a change in price. It is calculated using the midpoint formula:
需求价格弹性（PED）衡量需求量对价格变化的反应程度。用中点公式计算：
E = | [(Q₂ − Q₁) / ((Q₂ + Q₁)/2) ] / [ (P₂ − P₁) / ((P₂ + P₁)/2) ] |
If |E| > 1, demand is elastic — consumers are highly responsive. If |E| < 1, demand is inelastic. Unit elastic demand (|E| = 1) means percentage change in quantity equals percentage change in price. Total revenue moves in the direction of the price change when demand is inelastic, and opposite when elastic.
若 |E| > 1，需求富有弹性——消费者反应强烈。若 |E| < 1，需求缺乏弹性。单位弹性（|E| = 1）意味着需求量变动的百分比等于价格变动的百分比。当需求缺乏弹性时，总收益与价格同向变动；富有弹性时则反向变动。
6. Consumer Surplus and Producer Surplus | 消费者剩余与生产者剩余
Consumer surplus is the difference between the maximum price a buyer is willing to pay and the actual market price paid. It is the area below the demand curve and above the price line, representing the net benefit to consumers.
消费者剩余是买家愿意支付的最高价格与实际支付市场价格之间的差额。它是需求曲线下方、价格线上方的面积，代表消费者的净收益。
Producer surplus is the difference between the minimum price a seller is willing to accept and the market price received. It is the area above the supply curve and below the price line. Total surplus (consumer + producer) is maximised at competitive equilibrium, signalling allocative efficiency.
生产者剩余是卖家愿意接受的最低价格与实际收到的市场价格之间的差额。它是供给曲线上方、价格线下方的面积。总剩余（消费者剩余 + 生产者剩余）在竞争均衡处最大化，标志着配置效率。
7. Price Ceilings and Floors | 价格上限与下限
A price ceiling is a legal maximum price set below the equilibrium price, typically to protect consumers. It creates a persistent shortage, as quantity demanded exceeds quantity supplied at the capped price. Common examples include rent control.
价格上限是设定在均衡价格之下的法定最高价格，通常旨在保护消费者。它会造成持续性短缺，因为在该限价下需求量超过供给量。常见的例子包括租金管制。
A price floor is a legal minimum price set above equilibrium, often used to support producers. It leads to a surplus, with quantity supplied exceeding quantity demanded. Minimum wage laws are a classic case, potentially causing unemployment if set too high.
价格下限是设定在均衡价格之上的法定最低价格，常用于支持生产者。它会导致过剩，供给量超过需求量。最低工资法是一个典型案例，若设定过高可能引起失业。
Both price controls generate deadweight loss, reducing total surplus and creating inefficiency in the market.
价格上下限都会产生无谓损失，减少总剩余并造成市场效率低下。
8. Taxes and Deadweight Loss | 税收与无谓损失
When a per-unit tax is imposed, it drives a wedge between the price buyers pay and the price sellers receive. The tax burden is shared between consumers and producers, with the more inelastic side bearing a greater share.
当征收从量税时，会在买家支付的价格与卖家收到的价格之间造成楔子。税负由消费者和生产者分担，弹性较小的一方承担更多份额。
Taxes reduce the quantity traded below the efficient level, creating a deadweight loss (DWL). DWL represents the lost gains from trade that neither the government nor market participants capture. The larger the elasticities of demand and supply, the greater the deadweight loss.
税收使交易量降至有效水平以下，产生无谓损失（DWL）。无谓损失代表政府或市场参与者都没有获得的贸易利益损失。需求与供给弹性越大，无谓损失就越大。
9. Externalities | 外部性
Externalities are costs or benefits that affect third parties not directly involved in a transaction. A negative externality, like pollution, imposes an external cost on society, leading to overproduction. A positive externality, such as education, generates external benefits, causing underproduction.
外部性是指影响未直接参与交易的第三方的成本或收益。负外部性（如污染）给社会带来外部成本，导致生产过剩。正外部性（如教育）产生外部收益，导致生产不足。
Government can correct negative externalities with a Pigouvian tax equal to the marginal external cost, shifting the supply curve leftward. Positive externalities can be addressed with subsidies equal to the marginal external benefit, increasing quantity consumed to the socially optimal level.
政府可通过征收等于边际外部成本的庇古税来纠正负外部性，使供给曲线左移。正外部性可通过对等于边际外部效益的补贴来应对，将消费量提升至社会最优水平。
10. Public Goods and Common Resources | 公共物品与公共资源
Public goods are non-rival (one person’s consumption does not reduce availability to others) and non-excludable (people cannot be prevented from using them). National defence and street lighting are examples. The free-rider problem occurs because individuals have no incentive to pay, leading to underprovision by private markets.
公共物品具有非竞争性（一人消费不减少他人可用量）和非排他性（无法阻止人们使用）。国防和路灯就是例子。搭便车问题出现的原因是个人没有付款的动力，导致私人市场供给不足。
Common resources are rival but non-excludable, such as fisheries or clean air. They are subject to the tragedy of the commons, where individuals overuse and deplete the resource. Solutions include regulation, tradable permits, or assigning property rights.
公共资源具有竞争性但非排他性，如渔业或清洁空气。它们面临公地悲剧，即个人过度使用并耗尽资源。解决办法包括监管、可交易许可证或确立产权。
11. Costs of Production | 生产成本
In the short run, firms face fixed costs (FC) that do not vary with output, and variable costs (VC) that change with output. Total cost (TC) = FC + VC. Marginal cost (MC) = ΔTC / ΔQ. Average fixed cost (AFC) declines as output rises, while average variable cost (AVC) and average total cost (ATC) are typically U-shaped.
在短期，企业面临不随产量变动的固定成本（FC）和随产量变动的可变成本（VC）。总成本（TC）= FC + VC。边际成本（MC）= ΔTC / ΔQ。平均固定成本（AFC）随产量上升而下降，而平均可变成本（AVC）和平均总成本（ATC）通常呈 U 形。
The MC curve intersects both AVC and ATC at their minimum points. When MC is below average cost, average cost falls; when MC is above, average cost rises. The downward-sloping portion of ATC reflects spreading fixed costs over more units.
MC 曲线在 AVC 和 ATC 的最低点与其相交。当 MC 低于平均成本时，平均成本下降；当 MC 高于平均成本时，平均成本上升。ATC 下降段反映了固定成本分摊到更多单位上。
12. Market Structures | 市场结构
Perfect competition features many small firms, identical products, no barriers to entry, and price-taking behaviour. Individual firms face a perfectly elastic demand curve at the market price. In the long run, economic profit is zero (P = ATC), and productive efficiency (P = min ATC) as well as allocative efficiency (P = MC) are achieved.
完全竞争具有众多小企业、同质产品、无进入壁垒和价格接受者行为等特征。单个企业面临一条在市场价格上的完全弹性需求曲线。长期中，经济利润为零（P = ATC），并实现生产效率（P = 最低 ATC）和配置效率（P = MC）。
Monopoly exists when a single firm dominates the market with high barriers to entry. The monopolist is a price maker and faces a downward-sloping market demand curve. Profit maximisation occurs where MR = MC, but price is set above MC, creating deadweight loss and allocative inefficiency.
垄断指单一企业主导市场且进入壁垒较高。垄断者是价格制定者，面临向下倾斜的市场需求曲线。利润最大化于 MR = MC 处，但价格设定在 MC 之上，产生无谓损失和配置无效率。
Other structures include monopolistic competition (differentiated products, some market power, zero long-run economic profit) and oligopoly (few interdependent firms, strategic behaviour). Understanding these structures helps analyse real-world pricing and output decisions.
其他结构包括垄断竞争（产品差异化、一定的市场势力、长期经济利润为零）和寡头垄断（少数相互依存的企业、策略行为）。理解这些结构有助于分析现实中的定价与产量决策。
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