A-Level WJEC Economics: Last-Minute Revision Notes | A-Level WJEC 经济：考前冲刺笔记

📚 A-Level WJEC Economics: Last-Minute Revision Notes | A-Level WJEC 经济：考前冲刺笔记

These last-minute revision notes cover key microeconomic and macroeconomic concepts for the WJEC A-Level Economics specification. Use them to quickly review definitions, diagrams, and policy evaluations before your exam.

这些考前冲刺笔记涵盖了 WJEC A-Level 经济考试大纲中的关键微观和宏观经济概念。在考试前使用它们快速复习定义、图表和政策评估。

1. Scarcity and Choice | 稀缺性与选择

Economics studies the allocation of scarce resources to satisfy unlimited wants. The fundamental economic problem is scarcity.

经济学研究稀缺资源的分配以满足无限需求。基本经济问题是稀缺性。

The four factors of production are land, labour, capital, and enterprise. Their rewards are rent, wages, interest, and profit respectively.

四种生产要素是土地、劳动力、资本和企业才能。它们的报酬分别是地租、工资、利息和利润。

A production possibility frontier (PPF) shows the maximum combinations of two goods an economy can produce with fixed resources. Points on the curve are efficient; inside is inefficient; outside is unattainable.

生产可能性边界显示一个经济体在固定资源下能够生产的两种商品的最大组合。曲线上各点是有效率的；内部是无效率的；外部是无法达到的。

Opportunity cost is the value of the next best alternative sacrificed. The PPF illustrates this: moving along the curve incurs an opportunity cost.

机会成本是所放弃的次优替代品的价值。PPF 体现了这一点：沿着曲线移动会产生机会成本。

Economic growth shifts the PPF outward, caused by increased resources or better technology.

经济增长使 PPF 向外移动，这是由资源增加或技术进步引起的。

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2. Supply and Demand | 供给和需求

The law of demand states that as price rises, quantity demanded falls (ceteris paribus). The demand curve slopes downward.

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。需求曲线向下倾斜。

Factors shifting demand (non-price determinants) include income, tastes, price of substitutes/complements, expectations, and number of buyers.

导致需求移动的因素（非价格决定因素）包括收入、偏好、替代品/互补品的价格、预期和买者数量。

The law of supply states that as price rises, quantity supplied rises. The supply curve slopes upward.

供给定律指出，价格上升，供给量上升。供给曲线向上倾斜。

Supply shifters include production costs, technology, taxation/subsidies, weather, and number of sellers.

供给移动因素包括生产成本、技术、税收/补贴、天气和卖者数量。

Market equilibrium occurs where demand equals supply. Excess demand pushes prices up; excess supply pushes prices down.

市场均衡发生在需求等于供给时。超额需求推动价格上涨；超额供给推动价格下跌。

Consumer surplus is the difference between what consumers are willing to pay and what they actually pay. Producer surplus is the difference between the market price and the minimum price suppliers are willing to accept.

消费者剩余是消费者愿意支付与实际支付之间的差额。生产者剩余是市场价格与供应商愿意接受的最低价格之间的差额。

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3. Elasticity | 弹性

Price elasticity of demand (PED) measures responsiveness of quantity demanded to a change in price.

需求的价格弹性 (PED) 衡量需求量对价格变化的反应程度。

PED = %ΔQd ÷ %ΔP

PED > 1: elastic demand (revenue rises if price falls). PED < 1: inelastic demand. PED = 1: unitary elastic. PED = 0: perfectly inelastic, PED = ∞: perfectly elastic.

PED > 1: 弹性需求（价格下降收入增加）。PED < 1: 缺乏弹性需求。PED = 1: 单位弹性。PED = 0: 完全无弹性，PED = ∞: 完全弹性。

Determinants of PED: number of substitutes, proportion of income, luxury vs necessity, time period.

PED 的决定因素：替代品数量、收入比例、奢侈品与必需品、时间周期。

Income elasticity of demand (YED): %ΔQd ÷ %ΔY. Normal goods have positive YED; inferior goods negative. Luxury goods have YED > 1.

需求的收入弹性 (YED)：%ΔQd ÷ %ΔY。正常商品具有正的 YED；低档商品为负。奢侈品 YED > 1。

Cross elasticity of demand (XED): %ΔQd of good A ÷ %ΔP of good B. Substitutes have positive XED; complements negative.

需求的交叉弹性 (XED)：商品 A 的需求量变化百分比 ÷ 商品 B 价格变化百分比。替代品 XED 为正；互补品为负。

Price elasticity of supply (PES): %ΔQs ÷ %ΔP. Affected by time period and spare capacity.

供给的价格弹性 (PES)：%ΔQs ÷ %ΔP。受时间和闲置产能影响。

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4. Market Failure | 市场失灵

Market failure occurs when the free market fails to allocate resources efficiently, leading to a net social welfare loss.

市场失灵发生在自由市场不能有效配置资源时，导致社会净福利损失。

Types: externalities (positive and negative), public goods, information gaps, monopoly power, and inequality.

类型包括：外部性（正和负）、公共物品、信息不对称、垄断力量和不平等。

Negative production externality: e.g., pollution. Social cost > private cost, leading to overproduction. Diagram: MSC > MPC.

负生产外部性：例如污染。社会成本 > 私人成本，导致生产过剩。图形：MSC > MPC。

Negative consumption externality: e.g., passive smoking. Social benefit < private benefit. Overconsumption.

负消费外部性：例如二手烟。社会收益 < 私人收益。过度消费。

Positive externality: social benefit > private benefit; underconsumption or underproduction. E.g., education, healthcare.

正外部性：社会收益 > 私人收益；消费不足或生产不足。例如教育、医疗。

Public goods are non-rival and non-excludable, causing the free-rider problem. Examples: street lighting, national defence.

公共物品是非竞争性和非排他性的，会产生搭便车问题。例如路灯、国防。

Information asymmetry: one party knows more than the other, leading to adverse selection or moral hazard.

信息不对称：一方比另一方知道更多，导致逆向选择或道德风险。

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5. Government Intervention | 政府干预

Governments intervene to correct market failure and improve equity. Methods include taxation, subsidies, regulation, and state provision.

政府干预以纠正市场失灵并改善公平。方法包括税收、补贴、监管和国家提供。

Indirect tax (e.g., on demerit goods) shifts supply left, internalising the externality. Can be a specific tax (fixed amount) or ad valorem (percentage).

间接税（如对有害品）使供给左移，将外部性内部化。可为单位税（固定数额）或从价税（百分比）。

Subsidies shift supply right, encouraging merit goods. They lower price and increase quantity, but have an opportunity cost and may cause inefficiency.

补贴使供给右移，鼓励优值品。降低价格、增加产量，但有机会成本并可能导致低效率。

Maximum price (ceiling) set below equilibrium prevents price from rising, causing excess demand. Example: rent controls.

最高限价（上限）设在均衡价格之下，防止价格上升，造成超额需求。例如租金管制。

Minimum price (floor) set above equilibrium (e.g., minimum wage, agricultural price floor) causes excess supply.

最低限价（下限）设在均衡价格之上（如最低工资、农产品价格下限），造成超额供给。

Regulation: laws requiring or banning certain activities (e.g., smoking ban, emissions standards). Can be

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