📚 AP Microeconomics Comprehensive Review Outline | AP微观经济学全面复习提纲
This comprehensive review outline covers all major topics tested on the AP Microeconomics exam. Use it to reinforce key concepts, interpret graphs, and practice applying economic reasoning. Each section pairs English explanations with Chinese translations to support bilingual learners.
这份全面复习提纲覆盖了 AP 微观经济学考试的所有主要主题。用它来巩固关键概念、解读图表并练习运用经济学推理。每个部分都配有中英文解释，以帮助双语学习者。
1. Basic Economic Concepts | 基本经济概念
Scarcity forces individuals and societies to make choices because resources are limited. Every choice involves an opportunity cost, which is the value of the next best alternative forgone.
稀缺性迫使个人和社会做出选择，因为资源是有限的。每个选择都涉及机会成本，即所放弃的次优选项的价值。
Rational decision-making compares marginal benefits (MB) and marginal costs (MC). The optimal choice occurs where MB = MC, rather than considering total or average values.
理性决策会比较边际收益 (MB) 和边际成本 (MC)。最优选择出现在 MB = MC 处，而不是考虑总量或平均值。
The production possibilities curve (PPC) illustrates trade-offs and opportunity costs. Points inside the curve are inefficient, points outside are unattainable, and a bowed-out shape reflects the law of increasing opportunity cost.
生产可能性曲线 (PPC) 说明了权衡与机会成本。曲线内的点代表效率低下，曲线外的点无法达到，而向外凸出的形状反映了机会成本递增规律。
Comparative advantage explains why trade is beneficial. A nation should specialize in the good it can produce at a lower opportunity cost. The terms of trade must lie between the two countries’ opportunity costs.
比较优势解释了贸易为何有利。一个国家应专门生产其机会成本较低的商品。贸易条件必须介于两国的机会成本之间。
2. Demand, Supply, and Equilibrium | 需求、供给与均衡
The law of demand states that as price rises, quantity demanded falls, ceteris paribus. The demand curve can shift due to changes in income, preferences, prices of related goods, expectations, and number of buyers.
需求定律指出，在其他条件不变的情况下，价格上升，需求量下降。需求曲线会因收入、偏好、相关商品价格、预期和买家数量的变化而移动。
The law of supply shows that as price rises, quantity supplied increases. Supply shifters include input costs, technology, taxes/subsidies, producer expectations, and number of sellers.
供给定律表明，价格上升，供给量增加。供给曲线的移动因素包括投入成本、技术、税收/补贴、生产者预期和卖家数量。
Market equilibrium occurs where quantity demanded equals quantity supplied. A surplus above equilibrium pushes price down, while a shortage below equilibrium pushes price up.
市场均衡发生在需求量等于供给量之处。均衡之上的盈余会压低价格，均衡之下的短缺会推高价格。
Government-imposed price ceilings create persistent shortages when set below equilibrium (e.g., rent control). Price floors create surpluses when set above equilibrium (e.g., minimum wage for labor markets).
政府设定的价格上限若低于均衡，会导致持续的短缺（如租金管制）。价格下限若高于均衡，则产生盈余（如劳动力市场的最低工资）。
3. Elasticity | 弹性
Price elasticity of demand (PED) measures responsiveness of quantity demanded to a price change. The basic formula is:
需求价格弹性 (PED) 衡量需求量对价格变化的反应程度。基本公式如下：
E_d = (%ΔQ_d) / (%ΔP)
Using the midpoint method avoids discrepancy between different starting points:
使用中点法可避免不同起点带来的差异：
(Q₂ – Q₁) / [(Q₁ + Q₂)/2] ÷ (P₂ – P₁) / [(P₁ + P₂)/2]
Demand is elastic if |E_d| > 1 (consumers responsive), inelastic if |E_d| < 1, and unit elastic if |E_d| = 1. The total revenue test links elasticity to revenue changes: raising price increases total revenue if demand is inelastic, and decreases it if demand is elastic.
如果 |E_d| > 1，需求有弹性（消费者反应敏感）；如果 |E_d| < 1，需求缺乏弹性；如果 |E_d| = 1，则单位弹性。总收入检验将弹性与收入变化联系起来：若需求缺乏弹性，提价会提高总收入；若需求有弹性，提价则降低总收入。
Determinants of PED include availability of substitutes, time horizon, definition of the market (narrow vs. broad), and whether the good is a necessity or luxury. Cross-price elasticity and income elasticity further classify goods as substitutes/complements or normal/inferior.
PED 的决定因素包括替代品的可得性、时间跨度、市场定义的范围（窄 vs. 宽）以及商品是必需品还是奢侈品。交叉价格弹性和收入弹性进一步将商品分为替代品/互补品或正常品/低档品。
4. Consumer Choice and Utility | 消费者选择与效用
Utility measures satisfaction. Total utility increases with consumption, but marginal utility diminishes as more units are consumed (law of diminishing marginal utility).
效用衡量满足程度。总效用随消费增加而上升，但边际效用随着消费更多单位而递减（边际效用递减规律）。
Consumers maximize utility by allocating income so that the last dollar spent on each good yields the same marginal utility per dollar:
消费者通过分配收入使花费在每种商品上的最后一美元带来相同的边际效用，从而实现效用最大化：
MUₓ / Pₓ = MUᵧ / Pᵧ
The budget constraint shows all combinations of two goods a consumer can afford. Its slope equals the ratio of prices (–Pₓ / Pᵧ). The optimal consumption bundle occurs where the indifference curve is tangent to the budget line (MRS = price ratio).
预算约束显示了消费者能够承担的所有两种商品组合。其斜率等于价格比（–Pₓ / Pᵧ）。最优消费组合出现在无差异曲线与预算线相切之处（边际替代率等于价格比）。
5. Production and Costs | 生产与成本
In the short run, at least one input is fixed; in the long run, all inputs are variable. The production function shows the relationship between inputs and output. Marginal product initially rises but eventually falls due to diminishing marginal returns.
在短期内，至少有一种投入是固定的；在长期内，所有投入均可变。生产函数反映了投入与产出之间的关系。边际产量最初上升，但最终因边际报酬递减而下降。
Costs are divided into total fixed cost (TFC) and total variable cost (TVC). Total cost (TC) = TFC + TVC. Average costs (AFC, AVC, ATC) and marginal cost (MC) are crucial for profit analysis. MC cuts AVC and ATC at their minimum points.
成本分为总固定成本 (TFC) 和总可变成本 (TVC)。总成本 (TC) = TFC + TVC。平均成本 (AFC, AVC, ATC) 与边际成本 (MC) 对利润分析至关重要。MC 曲线穿过 AVC 和 ATC 曲线的最低点。
The long-run average total cost (LRATC) curve shows the lowest possible average cost when all inputs are flexible. Downward-sloping LRATC indicates economies of scale; upward-sloping signals diseconomies of scale.
长期平均总成本 (LRATC) 曲线显示了所有投入均可变时的最低可能平均成本。向下倾斜的 LRATC 表示规模经济；向上倾斜则表明规模不经济。
6. Perfect Competition | 完全竞争
Perfect competition features many small firms, identical products, free entry/exit, and perfect information. Firms are price takers, facing a perfectly elastic demand curve at the market price. The firm’s demand equals marginal revenue (MR) and average revenue (AR).
完全竞争具有许多小厂商、同质产品、自由进出和信息充分的特点。厂商是价格接受者，面临在市场价格处完全弹性的需求曲线。厂商的需求等于边际收益 (MR) 和平均收益 (AR)。
A firm maximizes profit where MR = MC. In the short run, it earns economic profit if P > ATC, breaks even if P = ATC, and may continue operating if AVC ≤ P < ATC but shut down if P < AVC.
厂商在 MR = MC 处实现利润最大化。短期内，若 P > ATC，可获得经济利润；若 P = ATC，盈亏平衡；若 AVC ≤ P < ATC，可继续运营；若 P < AVC，则停业。
In the long run, entry and exit drive price to the minimum ATC, yielding normal profit. Perfect competition achieves both productive efficiency (P = min ATC) and allocative efficiency (P = MC).
长期中，进出市场使价格趋向最低 ATC，利润为正常利润。完全竞争同时实现生产效率 (P = min ATC) 和配置效率 (P = MC)。
7. Imperfect Competition: Monopoly | 不完全竞争：垄断
A monopoly is a single seller with high barriers to entry. The firm faces a downward-sloping market demand curve, meaning MR lies below price. To sell one more unit, the monopolist must lower the price on all previous units.
垄断是拥有高进入壁垒的单一卖方。厂商面临向下倾斜的市场需求曲线，这意味着 MR 低于价格。为多卖一单位，垄断者必须对所有先前单位降价。
The monopolist produces where MR = MC but sets price off the demand curve, resulting in a higher price and lower quantity than perfect competition. This creates deadweight loss and is allocatively inefficient (P > MC).
垄断者在 MR = MC 处生产，但根据需求曲线定价，导致价格更高、产量低于完全竞争。这造成无谓损失，且配置无效率 (P > MC)。
Price discrimination allows a monopolist to charge different prices to different consumers, capturing some consumer surplus. Perfect price discrimination eliminates deadweight loss but transfers all surplus to the producer.
价格歧视让垄断者向不同消费者收取不同价格，攫取部分消费者剩余。完全价格歧视消除了无谓损失，但将全部剩余转移给了生产者。
8. Monopolistic Competition and Oligopoly | 垄断竞争与寡头
Monopolistic competition includes many firms with differentiated products and low barriers. In the short run, firms can earn economic profits or losses; in the long run, entry shifts demand left until P = ATC, yielding normal profit. Firms do not produce at minimum ATC, leading to excess capacity.
垄断竞争中有众多厂商，产品存在差异，进入壁垒低。短期内厂商可能获得经济利润或亏损；长期中进入使需求左移，直至 P = ATC，利润为正常利润。厂商未在最低 ATC 处生产，造成产能过剩。
Oligopoly is characterized by a few interdependent firms. Strategic behavior is central. The kinked demand curve model explains price rigidity, while game theory tools like the prisoner’s dilemma illustrate collusion and Nash equilibrium.
寡头市场由少数相互依赖的厂商构成。策略行为是核心。弯折的需求曲线模型解释了价格刚性，而囚徒困境等博弈论工具则阐释了合谋与纳什均衡。
A dominant strategy is one that is best regardless of the rival’s move. A Nash equilibrium occurs when each player chooses the best response given the other’s action. Collusion can increase joint profits but is often unstable due to incentives to cheat.
占优策略是指无论对手如何行动都是最佳选择的策略。当每个参与者在对方行动给定的情况下都选择了最佳应对时，就形成了纳什均衡。合谋可增加联合利润，但因存在欺骗动机而往往不稳定。
9. Factor Markets | 要素市场
Demand for factors of production, such as labor, is derived from the demand for the goods they produce. A firm hires workers as long as the marginal revenue product (MRP) exceeds the marginal factor cost (MFC).
对劳动力等生产要素的需求源于对其所生产商品的需求。只要边际收益产量 (MRP) 超过边际要素成本 (MFC)，厂商就会雇用工人。
For a perfectly competitive labor market, the wage is constant and equal to MFC; the firm hires where MRP = wage. MRP = MP × MR (or MP × P for price-taking firms).
在完全竞争的劳动力市场上，工资恒定且等于 MFC；厂商在 MRP = 工资处雇用。MRP = MP × MR（对价格接受者而言，MRP = MP × P）。
A monopsony is a single buyer of labor. To hire an additional worker, it must raise the wage for all, so MFC > wage. This results in lower employment and wage compared to a competitive market. A minimum wage set above the monopsony wage can boost both employment and wage.
买方垄断是劳动力的单一买方。为雇用更多工人，它必须提高所有工人的工资，因此 MFC > 工资。这导致与竞争市场相比更低的就业量和工资。设定在买方垄断工资之上的最低工资可以同时提高就业和工资。
10. Market Failure and Government Intervention | 市场失灵与政府干预
Market failure occurs when the free market fails to allocate resources efficiently. Negative externalities cause overproduction because private cost < social cost; positive externalities cause underproduction because private benefit < social benefit. The socially optimal quantity is where MSB = MSC.
市场失灵是指自由市场未能有效配置资源。负外部性导致过度生产，因私人成本 < 社会成本；正外部性导致生产不足，因私人收益 < 社会收益。社会最优数量在 MSB = MSC 处。
Government can correct externalities with taxes (equal to marginal external cost) or subsidies (equal to marginal external benefit). Direct regulation and tradable pollution permits are also used. The Coase theorem suggests private bargaining can solve externalities if property rights are well-defined and transaction costs are low.
政府可通过税收（等于边际外部成本）或补贴（等于边际外部收益）来纠正外部性。直接管制和可交易的污染许可也会被使用。科斯定理表明，只要产权明确且交易成本低，私人协商可以解决外部性问题。
Public goods are non-rival and non-excludable, leading to the free-rider problem and underprovision by private markets. Government often provides them. Income inequality is measured by the Lorenz curve and Gini coefficient, and governments may use taxes and transfers to redistribute.
公共物品具有非竞争性和非排他性，导致搭便车问题和私人市场供给不足，通常由政府提供。收入不平等由洛伦兹曲线和基尼系数衡量，政府可使用税收和转移支付进行再分配。
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