📚 IB & WJEC Economics: Last-Minute Revision Notes | IB & WJEC 经济学：考前冲刺笔记
This last-minute revision guide provides concise, high-yield notes covering both IB and WJEC Economics syllabi. Focus on key definitions, diagrams, and analytical chains to maximise your exam performance. Where topics diverge, IB-specific and WJEC-specific insights are clearly highlighted.
这本考前冲刺笔记提供简洁高效的复习要点，涵盖 IB 和 WJEC 经济学大纲。重点掌握关键定义、图形和分析链条，在考试中争取最佳表现。凡有差异之处，均明确标注 IB 专属或 WJEC 专属要点。
1. Microeconomics Foundations: Scarcity, Choice, and Opportunity Cost | 微观基础：稀缺性、选择与机会成本
The basic economic problem arises because resources are limited while wants are infinite, forcing economic agents to make choices. This fundamental concept underpins both syllabi.
基本经济问题源于资源有限而欲望无穷，迫使经济主体做出选择。这一基础概念贯穿两个考纲。
Opportunity cost is the next best alternative foregone when a choice is made. In WJEC, you must apply it to consumers, firms, and governments. For IB, link it to the production possibility frontier and real-world policy trade-offs.
机会成本是指做出某种选择时所放弃的次优替代品。WJEC 要求将机会成本应用于消费者、企业和政府。IB 则需要将其与生产可能性边界和现实政策权衡联系起来。
The Production Possibility Frontier (PPF) illustrates scarcity, choice, opportunity cost, and efficiency. A point inside the curve shows unemployment or inefficiency; an outward shift indicates economic growth. For IB, be ready to draw and shift the PPF for two goods, e.g., capital and consumer goods.
生产可能性边界 (PPF) 说明了稀缺性、选择、机会成本和效率。曲线内的点表示失业或低效率；向外移动表示经济增长。IB 考生需能画出两种商品的 PPF 移动，如资本品与消费品。
2. Demand, Supply, and Market Equilibrium | 需求、供给与市场均衡
The law of demand states that as price falls, quantity demanded rises, ceteris paribus. Factors shifting the demand curve include income (inferior vs normal goods), tastes, prices of substitutes and complements, and demographics.
需求定律指出，其他条件不变时，价格下跌则需求量上升。导致需求曲线移动的因素包括收入（低档品与正常品）、偏好、替代品和互补品的价格、人口统计等。
Supply curves slope upward: higher prices incentivise firms to produce more. Shifts in supply arise from changes in costs of production, technology, taxes, subsidies, or ‘shocks’ such as weather.
供给曲线向上倾斜：更高的价格激励企业增加产出。供给移动源于生产成本、技术、税收、补贴变化或天气等冲击。
Equilibrium occurs where quantity demanded equals quantity supplied. Disequilibrium creates excess demand (shortage) or excess supply (surplus), driving price changes. Use the ‘step method’ to analyse shifts: identify the shock, determine which curve shifts, and read the new equilibrium price and quantity.
均衡出现在需求量等于供给量之处。非均衡会造成超额需求（短缺）或超额供给（过剩），进而推动价格调整。使用 ‘三步法’ 分析变动：识别冲击、判断哪条曲线移动、读取新的均衡价格与数量。
- Excess demand pushes price up; excess supply pushes price down. 超额需求推高价格；超额供给压低价格。
- Both IB and WJEC require clear, well-labelled diagrams showing price (P) and quantity (Q). IB 和 WJEC 均要求绘制标注清晰的 P-Q 图示。
3. Elasticities: PED, PES, YED, XED | 弹性：需求价格弹性、供给价格弹性、收入弹性、交叉弹性
Price elasticity of demand (PED) measures the responsiveness of quantity demanded to a change in price.
需求价格弹性 (PED) 衡量需求量对价格变动的反应程度。
PED = %ΔQd / %ΔP
| Value | Classification | Effect on Revenue |
|---|---|---|
| > 1 | Elastic | Price rise → TR falls; Price cut → TR rises |
| < 1 | Inelastic | Price rise → TR rises; Price cut → TR falls |
| = 1 | Unit elastic | TR unchanged |
Price elasticity of supply (PES) depends on time period, spare capacity, and storability. Income elasticity (YED) distinguishes normal goods (positive) and inferior goods (negative); cross elasticity (XED) identifies substitutes (positive) and complements (negative). WJEC often tests elasticity through data and calculations; IB Paper 3 expects precise interpretation and evaluation.
供给价格弹性 (PES) 取决于时段、闲置产能和可储存性。收入弹性 (YED) 区分正常品（正值）与低档品（负值）；交叉弹性 (XED) 识别替代品（正值）与互补品（负值）。WJEC 常通过数据和计算考查弹性；IB 试卷三要求准确解释与评估。
4. Market Failure and Government Intervention | 市场失灵与政府干预
Market failure occurs when free markets fail to allocate resources efficiently. Key types include externalities (positive and negative), public goods (non-rival, non-excludable), information asymmetries, and imperfect competition.
市场失灵发生在自由市场无法有效配置资源时。主要类型包括外部性（正负）、公共物品（非竞争性、非排他性）、信息不对称和不完全竞争。
Negative production externalities create overproduction; diagram requires a shift of the MSC curve above MPC. A Pigouvian tax can internalise the externality. For positive externalities, underproduction occurs; subsidies can encourage more consumption.
负生产外部性导致过度生产；图形要求 MSC 曲线高于 MPC。庇古税可以内化外部成本。正外部性则导致生产不足；补贴可以鼓励增加消费。
- Government responses: indirect taxes, subsidies, regulations, tradable permits, state provision, and information campaigns. 政府对策：间接税、补贴、法规、可交易许可证、国家提供和信息宣传。
- IB exams expect evaluation of real-world measures, while WJEC integrates market failure into its micro essays and data response. IB 考试注重评估现实措施，WJEC 则将市场失灵融入微观论文和数据分析题。
5. Theory of the Firm and Market Structures (IB & WJEC) | 厂商理论与市场结构
Both syllabi require understanding of costs (fixed, variable, total, marginal, average) and revenues (total, marginal, average). The short run contains at least one fixed factor; the long run has all factors variable.
两个考纲均要求理解成本（固定、可变、总、边际、平均）和收益（总、边际、平均）。短期至少有一种固定要素；长期所有要素均可变。
The profit-maximising condition is MR = MC. Supernormal profit occurs when AR > AC; normal profit when AR = AC; losses when AR < AC. IB students must also draw cost/revenue curves for the four market structures: perfect competition, monopolistic competition, oligopoly, and monopoly. WJEC focuses on comparative market outcomes, concentration ratios, and efficiencies.
利润最大化条件为 MR = MC。当 AR > AC 时存在超额利润；AR = AC 时为正常利润；AR < AC 时出现亏损。IB 学生还需绘制四种市场结构的成本收益曲线：完全竞争、垄断竞争、寡头和垄断。WJEC 侧重比较市场结果、集中度和效率。
- Perfect competition: price takers, productive and allocative efficiency in long run. 完全竞争：价格接受者，长期实现生产效率和配置效率。
- Monopoly: price maker, potential welfare loss, can achieve dynamic efficiency. 垄断：价格制定者，可能出现福利损失，但能实现动态效率。
- Game theory (for IB oligopoly): prisoner’s dilemma and collusion. 博弈论（IB 寡头）：囚徒困境与共谋。
6. Macroeconomic Objectives and Circular Flow | 宏观经济目标与循环流动
Governments aim for: stable economic growth (IB: 2–3% for developed), low unemployment, low and stable inflation (2% target), balance of payments equilibrium, and equitable income distribution. WJEC also includes balanced government budget and environmental protection as macro objectives.
政府目标包括：稳定的经济增长（IB 发达经济体为 2–3%）、低失业率、低而稳定的通胀（2% 目标）、国际收支平衡、公平收入分配。WJEC 还将预算平衡和环境保护纳入宏观目标。
The circular flow model shows injections (investment, government spending, exports) and leakages (saving, taxation, imports). Equilibrium national income occurs when injections equal leakages. IB candidates must explain the two-sector, three-sector, and four-sector models with diagrams.
循环流动模型展示注入（投资、政府支出、出口）与漏出（储蓄、税收、进口）。当总注入等于总漏出时，国民收入达到均衡。IB 考生需解释两部门、三部门和四部门模型并配图。
7. Aggregate Demand and Aggregate Supply | 总需求与总供给
Aggregate Demand (AD) = C + I + G + (X – M). A fall in any component shifts AD left; a rise shifts it right. The AD curve slopes downward due to wealth, interest-rate, and trade effects.
总需求 (AD) = 消费 + 投资 + 政府支出 + (出口－进口)。任何组成部分下降都会使 AD 左移；上升则右移。AD 曲线向右下倾斜源于财富效应、利率效应和贸易效应。
Short-run Aggregate Supply (SRAS) slopes upward; shifts occur from changes in factor costs, taxes, or supply shocks. Long-run Aggregate Supply (LRAS) is vertical at full-employment output, representing the productive capacity of the economy. Shifts in LRAS come from changes in quantity/quality of resources, technology, and institutions.
短期总供给 (SRAS) 向上倾斜；要素成本、税收或供给冲击变化会引起移动。长期总供给 (LRAS) 在充分就业产出水平呈垂直线，代表经济产能。LRAS 的移动源于资源数量/质量、技术和制度的变化。
Draw an AD/AS diagram to illustrate demand-pull inflation, cost-push inflation, and the output gap. WJEC expects you to explain the multiplier using AD shifts, whereas IB requires the Keynesian multiplier calculation (k = 1/(1-MPC) or 1/MPW).
绘制 AD/AS 图示可以说明需求拉动型通胀、成本推动型通胀和产出缺口。WJEC 要求用 AD 移动解释乘数效应，IB 则要求计算凯恩斯乘数 (k = 1/(1-MPC) 或 1/MPW)。
8. Fiscal, Monetary, and Supply-Side Policies | 财政政策、货币政策与供给方政策
Fiscal policy involves government spending and taxation. Expansionary fiscal policy (higher spending, lower taxes) boosts AD; contractionary fiscal policy does the opposite. Automatic stabilisers (progressive taxes, welfare benefits) work without discretionary changes.
财政政策涉及政府支出和税收。扩张性财政政策（增加支出、减税）会提振 AD；紧缩性财政政策则相反。自动稳定器（累进税、福利给付）无需相机抉择即可发挥作用。
Monetary policy uses interest rates and the money supply, usually controlled by a central bank. Lower rates stimulate investment and consumption; higher rates cool the economy. Quantitative easing is an unconventional monetary tool for near-zero interest rates.
货币政策通过利率和货币供应量调控，一般由中央银行执行。降低利率刺激投资和消费；提高利率给经济降温。量化宽松是接近零利率时使用的非常规货币政策工具。
Supply-side policies aim to increase LRAS by improving productivity, competition, and labour-market flexibility. Examples: education and training, tax reforms, deregulation, infrastructure investment. For both IB and WJEC, evaluate time lags, cost, equity, and effectiveness in different economic contexts.
供给方政策旨在通过提高生产率、竞争力和劳动力市场灵活性来增加 LRAS。例：教育培训、税制改革、放松管制、基建投资。IB 和 WJEC 均需评估时滞、成本、公平性以及不同经济环境下的有效性。
9. International Trade, Exchange Rates, and Development (IB Focus) | 国际贸易、汇率与发展（IB 重点）
Comparative advantage explains why countries trade: even if one country is absolutely more efficient in all goods, gains occur if each specialises in the good with lower opportunity cost. Draw linear PPFs and identify comparative advantage using ratios or output tables.
比较优势解释贸易原因：即使一国在两种商品上均有绝对优势，只要各自专门生产机会成本较低的商品，仍能获益。用线性 PPF 和比率或产出表识别比较优势。
Protectionist measures (tariffs, quotas, subsidies to domestic producers) raise prices, reduce imports, and create welfare loss. For IB, analyse the diagram of a tariff showing government revenue, consumer loss, and deadweight loss. WJEC covers similar ground within its global economics modules.
保护主义措施（关税、配额、对国内生产者的补贴）推高价格、减少进口并造成福利损失。IB 需分析关税图示，展示政府收入、消费者损失和无谓损失。WJEC 在其全球经济学模块中涵盖类似内容。
Exchange rates: appreciation (stronger currency) makes exports dearer and imports cheaper, worsening net exports. Depreciation has the reverse effect. IB students must distinguish fixed, floating, and managed exchange-rate systems and evaluate their impact on the balance of payments.
汇率：升值（本币走强）使出口变贵、进口变便宜，净出口恶化。贬值则反之。IB 学生须区分固定、浮动和管理汇率制度，并评估其对国际收支的影响。
Economic development (IB exclusive depth) goes beyond GDP growth to include health, education, income distribution, and freedoms. Use indicators such as HDI, MPI, and the Lorenz curve/Gini coefficient. Trade strategies like import substitution and export-led growth must be assessed for their sustainability and equity impact.
经济发展（IB 深度独有）超越 GDP 增长，涵盖健康、教育、收入分配和自由。使用 HDI、MPI 和洛伦兹曲线/基尼系数等指标。评估进口替代和出口导向等贸易策略的可持续性与公平性影响。
10. Exam Technique: Data Response and Essay Skills | 考试技巧：数据分析题与论文写作
Read the stem carefully. For data response (IB Paper 2 & WJEC Unit 2/3), define key terms, reference figures, and use economic theory to explain trends. Always evaluate: consider short-run vs long-run effects, stakeholders, alternative policies, and limitations of data.
仔细阅读题干。数据分析题（IB 试卷二与 WJEC 单元 2/3）须定义关键词、引用图表数据，并用经济理论解释趋势。始终加入评估：考量短期与长期效应、利益相关者、替代政策及数据局限性。
- Structure essays: introduction (definitions + thesis), body paragraphs (PEEL — point, evidence, explain, link), evaluation, and conclusion. 论文结构：引言（定义+论点）、主体段落（PEEL——观点、证据、解释、联系）、评估与结论。
- IB candidates need real-world examples for 15-mark questions; WJEC A-Level requires context-based application. IB 考生需要在 15 分题中使用现实例子；WJEC A-Level 要求基于背景的应用。
- For IB Paper 3, practise calculations and policy commentary with precise AD/AS or micro diagrams. Time management is critical in both boards — allocate minutes proportional to marks. 针对 IB 试卷三，练习计算和政策评析并配精确的 AD/AS 或微观图示。时间管理在两边考试中都至关重要——按分值比例分配时间。
Review mark schemes: WJEC rewards chains of reasoning; IB rewards clear diagrams, appropriate terminology, and evaluation. Connect different topics — e.g., a micro externality question can be linked to government failure in macro policy.
重温评分标准：WJEC 奖励因果推理链条；IB 奖励清晰图示、恰当术语和评估。联系不同主题——例如微观外部性题目可以联系宏观政策中的政府失灵。
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