📚 AP Microeconomics Core Vocabulary Explained | AP微观经济核心词汇解析
Mastering AP Microeconomics begins with a clear understanding of its essential terminology. These core terms form the building blocks for analyzing individual decision-making, market structures, and efficiency. This guide defines and explains key microeconomic vocabulary in a bilingual, paired format to help you build a rock-solid conceptual foundation for the exam.
掌握AP微观经济学始于对其基本术语的清晰理解。这些核心词汇是分析个体决策、市场结构和效率的基础。本指南以中英双语、对照解析的形式定义并解释关键微观经济词汇，帮助你为考试构建坚如磐石的概念基础。
1. Scarcity, Choice, and Opportunity Cost | 稀缺性、选择与机会成本
Scarcity is the fundamental economic problem that arises because resources are limited while human wants are unlimited, forcing individuals and societies to make choices.
稀缺性是由于资源有限而人类欲望无限所产生的根本经济问题，迫使个人和社会做出选择。
Opportunity cost is the value of the next best alternative that must be forgone when a decision is made. It includes both explicit and implicit costs.
机会成本是做出决策时必须放弃的次优选择的价值。它包括显性成本和隐性成本。
The production possibilities curve (PPC) illustrates scarcity, trade-offs, and opportunity cost by showing the maximum combinations of two goods an economy can produce given its resources and technology.
生产可能性曲线（PPC）通过展示一个经济体在给定资源和技术下能生产的两种商品的最大组合，来阐明稀缺性、权衡取舍和机会成本。
Marginal analysis involves comparing the additional benefits of an action to its additional costs, which is central to economic decision-making.
边际分析包括比较一项行动的额外收益与额外成本，这是经济决策的核心。
2. Supply and Demand | 供给与需求
The law of demand states that, ceteris paribus, as the price of a good increases, the quantity demanded decreases, resulting in a downward-sloping demand curve.
需求定律指出，在其他条件不变的情况下，商品价格上升，需求量下降，导致需求曲线向下倾斜。
The law of supply states that, ceteris paribus, as the price of a good increases, the quantity supplied increases, resulting in an upward-sloping supply curve.
供给定律指出，在其他条件不变的情况下，商品价格上升，供给量上升，导致供给曲线向上倾斜。
A shift in demand is caused by changes in non-price determinants such as income, tastes, prices of related goods (substitutes and complements), expectations, and the number of buyers.
需求曲线的移动是由非价格决定因素的变化引起的，例如收入、偏好、相关商品（替代品和互补品）的价格、预期以及购买者数量。
A shift in supply is caused by changes in input prices, technology, expectations, the number of sellers, and government policies such as taxes and subsidies.
供给曲线的移动是由投入品价格、技术、预期、销售者数量以及税收和补贴等政府政策的变化引起的。
3. Elasticity | 弹性
Price elasticity of demand (PED) measures the responsiveness of quantity demanded to a change in price. It is calculated as PED = %ΔQd / %ΔP. If |PED| > 1, demand is elastic; if |PED| < 1, demand is inelastic; if |PED| = 1, demand is unit elastic.
需求价格弹性（PED）衡量需求量对价格变化的反应程度。计算公式为 PED = %ΔQd / %ΔP。若 |PED| > 1，需求富有弹性；若 |PED| < 1，需求缺乏弹性；若 |PED| = 1，需求具有单位弹性。
Price elasticity of supply (PES) measures how responsive quantity supplied is to a change in price. PES = %ΔQs / %ΔP. It depends on production flexibility and time horizon.
供给价格弹性（PES）衡量供给量对价格变化的反应程度。PES = %ΔQs / %ΔP。它取决于生产的灵活性和时间长度。
Income elasticity of demand (YED) is %ΔQd / %ΔIncome. Normal goods have positive YED; inferior goods have negative YED. Luxury goods have YED > 1.
需求收入弹性（YED）计算公式为 %ΔQd / %Δ收入。正常品的YED为正；劣等品的YED为负。奢侈品YED > 1。
Cross-price elasticity of demand (XED) is %ΔQd of good A / %ΔP of good B. Positive XED indicates substitutes; negative XED indicates complements.
需求交叉价格弹性（XED）为商品A需求量变化百分比除以商品B价格变化百分比。XED为正表示替代品；XED为负表示互补品。
4. Consumer and Producer Surplus | 消费者剩余与生产者剩余
Consumer surplus is the difference between what consumers are willing to pay (their maximum willingness) and what they actually pay, represented by the area below the demand curve and above the market price.
消费者剩余是消费者愿意支付的最高价格与市场价格之间的差额，在图形中表现为需求曲线以下、市场价格以上的区域。
Producer surplus is the difference between the price producers actually receive and the minimum price they are willing to accept (marginal cost), represented by the area above the supply curve and below the market price.
生产者剩余是生产者实际获得的价格与其愿意接受的最低价格（边际成本）之间的差额，表现为供给曲线以上、市场价格以下的区域。
Total surplus is the sum of consumer and producer surplus and serves as a measure of economic welfare. At competitive equilibrium, total surplus is maximized.
总剩余是消费者剩余与生产者剩余之和，是衡量经济福利的指标。在竞争均衡时，总剩余最大化。
Deadweight loss is the loss in total surplus that occurs when the market is not at the allocatively efficient equilibrium, often due to taxes, price controls, or externalities.
无谓损失是指市场未处于配置效率均衡时总剩余的减少，通常由税收、价格控制或外部性引起。
5. Market Equilibrium and Government Intervention | 市场均衡与政府干预
Market equilibrium occurs where quantity demanded equals quantity supplied, determining the equilibrium price and quantity. At this point, there is no shortage or surplus.
市场均衡发生在需求量等于供给量之处，由此决定均衡价格和数量。在该点，不存在短缺或过剩。
A price ceiling is a legal maximum price set below equilibrium, causing a persistent shortage. An example is rent control.
价格上限是设定在均衡价格以下的法定最高价格，会导致持续性短缺。例如租金管制。
A price floor is a legal minimum price set above equilibrium, causing a persistent surplus. An example is minimum wage in the labor market.
价格下限是设定在均衡价格以上的法定最低价格，会导致持续性过剩。例如劳动力市场的最低工资。
An excise tax shifts the supply curve upward by the amount of the tax, raising the price for buyers, lowering the price for sellers, and creating deadweight loss. The tax incidence depends on relative elasticities.
从量税使供给曲线向上移动税额的大小，提高买方价格，降低卖方价格，并产生无谓损失。税收负担取决于相对弹性。
A subsidy shifts the supply curve downward, lowering the price for buyers and raising the effective price for sellers, which increases quantity but also creates deadweight loss.
补贴使供给曲线向下移动，降低买方价格并提高卖方实际价格，增加数量但也产生无谓损失。
6. Production and Costs | 生产与成本
The short run is a period in which at least one factor of production is fixed, while the long run is a period in which all factors are variable.
短期是至少一种生产要素固定的时期，而长期是所有要素都可变的时期。
Total product (TP) is the total output produced. Marginal product (MP) is the additional output from one more unit of input. Diminishing marginal returns occur when MP begins to decline as more of a variable input is added to a fixed input.
总产量（TP）是生产的总产出。边际产量（MP）是增加一单位投入所带来的额外产出。当增加更多可变投入到固定投入上时，边际产量开始下降，即出现边际收益递减。
Total cost (TC) = total fixed cost (TFC) + total variable cost (TVC). Marginal cost (MC) is the change in TC from producing one more unit. Average total cost (ATC) = TC/Q.
总成本（TC）= 总固定成本（TFC）+ 总可变成本（TVC）。边际成本（MC）是多生产一单位产量带来的总成本变化。平均总成本（ATC）= TC/Q。
Economies of scale refer to falling long-run average total cost as output increases, while diseconomies of scale refer to rising ATC. Constant returns to scale occur when ATC is unchanged.
规模经济指随着产量增加长期平均总成本下降；规模不经济指平均总成本上升。规模收益不变时平均总成本保持不变。
7. Perfect Competition | 完全竞争
A perfectly competitive market has many small firms, identical products, no barriers to entry or exit, and perfect information. Firms are price takers, meaning they cannot influence the market price.
完全竞争市场拥有众多小型企业、同质产品、无进入或退出壁垒以及完全信息。企业是价格接受者，即无法影响市场价格。
In perfect competition, the demand curve facing the individual firm is perfectly elastic (horizontal) at the market price. The firm maximizes profit where MR = MC.
在完全竞争中，单个企业面临的需求曲线在市场价格处为完全弹性（水平）。企业在 MR = MC 处实现利润最大化。
In the long run, economic profits attract new entrants, shifting the supply curve right and lowering the price until firms earn zero economic profit (normal profit). This results in productive and allocative efficiency.
长期中，经济利润吸引新企业进入，使供给曲线右移并压低价格，直至企业仅获得零经济利润（正常利润）。此时实现了生产效率和配置效率。
8. Monopoly | 垄断
A monopoly exists when a single firm is the sole seller of a product with no close substitutes, and there are high barriers to entry. The firm is a price maker and faces the downward-sloping market demand curve.
当一家企业是一个无相近替代品的产品的唯一销售者，且存在高进入壁垒时，就形成了垄断。垄断企业是价格制定者，面临整个向下倾斜的市场需求曲线。
A monopolist maximizes profit where MR = MC, but since P < MR, the price charged is higher than marginal cost, which leads to allocative inefficiency and deadweight loss.
垄断者在 MR = MC 处实现利润最大化，但由于对于垄断者来说 P < MR，其要价高于边际成本，导致配置无效率和无谓损失。
A natural monopoly occurs when economies of scale are so large that a single firm can supply the entire market at a lower average total cost than two or more firms. Governments often regulate natural monopolies with price caps like average-cost pricing or marginal-cost pricing.
自然垄断出现在规模经济如此之大，以至于由一家企业供应整个市场的平均总成本低于两家或更多企业时。政府通常通过平均成本定价或边际成本定价等价格上限来监管自然垄断。
Price discrimination occurs when a monopolist charges different prices to different consumers for the same product, based on willingness to pay, to capture consumer surplus and increase profits.
价格歧视指垄断者根据支付意愿，就同一产品向不同消费者收取不同价格，以攫取消费者剩余并增加利润。
9. Monopolistic Competition and Oligopoly | 垄断竞争与寡头
Monopolistic competition features many firms, differentiated products, and low barriers to entry. Firms have some downward-sloping demand but face competition, earning zero economic profit in the long run.
垄断竞争具有众多企业、产品差异化和低进入壁垒的特征。企业面临一定程度的向下倾斜的需求曲线，但存在竞争，长期中经济利润为零。
In monopolistic competition, firms produce where MC = MR but operate with excess capacity and do not achieve productive efficiency, yet product variety may increase consumer welfare.
垄断竞争企业在 MC = MR 处生产，但存在产能过剩，未能实现生产效率，不过产品多样化可能增进消费者福利。
An oligopoly is a market dominated by a few large firms with high barriers to entry. Firms are interdependent; their pricing and output decisions depend on rivals’ expected reactions.
寡头市场由少数大企业主导，进入壁垒高。企业相互依赖，其定价和产量决策取决于对竞争对手反应的预期。
Game theory models strategic interdependence. The prisoner’s dilemma illustrates why oligopolists might collude or cheat. Collusion leads to joint profit maximization like a monopoly, but it is unstable due to incentives to cheat.
博弈论用于模拟策略性相互依赖。囚徒困境说明了寡头为何会合谋或欺骗。合谋可达到如同垄断的联合利润最大化，但由于存在欺骗动机，合谋往往不稳定。
10. Factor Markets | 要素市场
Factor markets are where factors of production (labor, capital, land) are bought and sold. The demand for a factor is derived from the demand for the goods and services it helps produce.
要素市场是买卖生产要素（劳动、资本、土地）的场所。对要素的需求是从对其所生产的商品和服务的需求中衍生出来的。
The marginal revenue product (MRP) of labor equals marginal product of labor times marginal revenue. A profit-maximizing firm hires workers up to the point where MRP = wage (MFC).
劳动的边际收益产品（MRP）等于劳动的边际产量乘以边际收益。利润最大化的企业会雇佣工人直到 MRP = 工资（MFC）为止。
In a perfectly competitive labor market, the firm is a wage taker. In a monopsony, a single buyer of labor faces an upward-sloping labor supply curve and pays a wage lower than MRP, causing inefficiency.
在完全竞争的劳动力市场中，企业是工资接受者。在买方垄断中，唯一的劳动力购买者面临向上倾斜的劳动供给曲线，支付的工资低于MRP，造成无效率。
11. Market Failure and Externalities | 市场失灵与外部性
Market failure occurs when the free market fails to allocate resources efficiently. Key causes include externalities, public goods, market power, and information asymmetry.
市场失灵是指自由市场无法有效配置资源的情况。主要原因包括外部性、公共品、市场势力和信息不对称。
A negative externality arises when a third party is harmed by a market activity (e.g., pollution). This leads to overproduction because the marginal social cost (MSC) exceeds the marginal private cost (MPC).
负外部性发生在第三方因市场活动而受损时（如污染）。由于边际社会成本（MSC）大于边际私人成本（MPC），这会导致过度生产。
A positive externality arises when a third party benefits from a market activity (e.g., education). This leads to underproduction because the marginal social benefit (MSB) exceeds the marginal private benefit (MPB).
正外部性发生在第三方从市场活动中受益时（如教育）。由于边际社会收益（MSB）大于边际私人收益（MPB），这会导致生产不足。
Pigouvian taxes (on negative externalities) and subsidies (on positive externalities) can internalize the externality, aligning private incentives with social efficiency.
庇古税（针对负外部性）和庇古补贴（针对正外部性）可以将外部性内部化，使私人激励与社会效率保持一致。
12. Public Goods and Common Resources | 公共品与公共资源
Public goods are non-rival (one person’s consumption does not reduce availability for others) and non-excludable (people cannot be prevented from using them). The free-rider problem leads to underprovision by private markets. National defense is a classic example.
公共品具有非竞争性（一人的消费不减少他人可用量）和非排他性（无法阻止人们使用）。搭便车问题导致私人市场供给不足。国防是典型例子。
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 a shared resource acting in their own self-interest.
公共资源具有竞争性但非排他性，如渔场或清洁空气。它们容易发生公地悲剧，即个人基于自身利益过度使用并耗竭共享资源。
Government solutions for common resources include quotas, tradable permits, or assignment of property rights to prevent overuse and align private and social interests.
针对公共资源的政府解决方案包括配额、可交易许可证或界定产权，以防止过度使用并使私人利益与社会利益一致。
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