📚 IB Economics: Last-Minute Revision Notes | IB经济：考前冲刺笔记
Welcome to your ultimate last-minute revision guide for IB Economics. This article distils key concepts, diagrams and evaluation points across microeconomics, macroeconomics, international economics and development economics, together with essential exam techniques to help you secure top marks.
欢迎阅读这份IB经济考前终极冲刺笔记。本文浓缩了微观经济学、宏观经济学、国际经济学和发展经济学的核心概念、图表和评估要点，并提供了关键的考试技巧，助你稳夺高分。
1. Scarcity and Choice | 稀缺性与选择
Economics is the study of how scarce resources are allocated to satisfy unlimited human wants. The basic economic problem arises because resources are finite while desires are infinite.
经济学研究稀缺资源如何配置以满足无限的人类欲望。基本经济问题源于资源有限而欲望无穷。
The concept of opportunity cost is central: it is the value of the next best alternative foregone when a choice is made. Every decision involves a trade-off.
机会成本概念至关重要：它是做出选择时所放弃的次优替代品的价值。每一个决策都涉及权衡取舍。
The production possibilities curve (PPC) shows the maximum combinations of two goods an economy can produce with full employment of resources. Points inside the curve indicate inefficiency or unemployment; an outward shift represents economic growth, often driven by more resources or better technology.
生产可能性曲线（PPC）展示了一个经济体在资源充分利用时能生产的两种商品的最大组合。曲线内的点表示无效率或失业；向外移动代表经济增长，通常由更多资源或技术进步驱动。
2. Demand and Supply | 需求与供给
The law of demand states that as the price of a good rises, the quantity demanded falls, ceteris paribus. It is explained by the substitution effect and the income effect.
需求定律表明，在其他条件不变的情况下，商品价格上涨时，需求量下降。这可以由替代效应和收入效应来解释。
The law of supply states that as price rises, the quantity supplied increases, because higher prices provide an incentive for producers to expand output.
供给定律表明，价格上涨时，供给量增加，因为更高的价格激励生产者扩大产出。
Market equilibrium occurs where demand equals supply. Factors that shift demand include income, tastes, prices of related goods and expectations. Supply shifters include input costs, technology, taxes and subsidies.
市场均衡发生在需求等于供给之处。需求移动的因素包括收入、偏好、相关商品价格和预期。供给移动的因素包括投入成本、技术、税收和补贴。
Government intervention through price ceilings (maximum prices) creates shortages, while price floors (minimum prices) lead to surpluses. Both cause welfare loss.
政府通过最高限价进行干预会造成短缺，而最低限价会导致过剩。两者都会造成福利损失。
3. Elasticity | 弹性
Price elasticity of demand (PED) measures the responsiveness of quantity demanded to a change in price. The formula is:
需求价格弹性（PED）衡量需求量对价格变化的反应程度。公式为：
PED = %ΔQd ÷ %ΔP
If |PED| > 1, demand is price elastic; if |PED| < 1, demand is price inelastic. PED determines the effect of price changes on total revenue and the incidence of a tax.
如果 |PED| > 1，需求是富有价格弹性的；如果 |PED| < 1，需求是缺乏价格弹性的。PED 决定价格变动对总收入的影响以及税收的归宿。
Price elasticity of supply (PES) measures the responsiveness of quantity supplied to price changes. It depends on the mobility of factors of production and time period.
供给价格弹性（PES）衡量供给量对价格变动的反应。它取决于生产要素的流动性和时间长短。
Cross elasticity of demand (XED) = %ΔQa ÷ %ΔPb. A positive XED indicates substitutes; a negative XED indicates complements.
需求交叉弹性 (XED) = %ΔQa ÷ %ΔPb。XED 为正表示替代品；为负表示互补品。
Income elasticity of demand (YED) = %ΔQd ÷ %ΔY. Normal goods have positive YED; inferior goods have negative YED. Luxury goods have YED > 1.
需求收入弹性 (YED) = %ΔQd ÷ %ΔY。正常品的 YED 为正；低档品的 YED 为负。奢侈品的 YED > 1。
4. Market Structures | 市场结构
Market structures range from perfect competition to monopoly. The key characteristics include the number of firms, type of product, barriers to entry, and control over price.
市场结构从完全竞争到垄断各不相同。关键特征包括企业数量、产品类型、进入壁垒以及对价格的控制力。
| Feature | 特征 |
|---|---|
| Perfect competition: many small firms, homogeneous product, no barriers, price taker | 完全竞争：众多小企业，同质产品，无壁垒，价格接受者 |
| Monopolistic competition: many firms, differentiated product, low barriers | 垄断竞争：许多企业，差异化产品，低壁垒 |
| Oligopoly: few dominant firms, interdependence, high barriers, non-price competition | 寡头垄断：少数主导企业，相互依存，高壁垒，非价格竞争 |
| Monopoly: single firm, unique product, very high barriers, price maker | 垄断：单一企业，独特产品，极高壁垒，价格制定者 |
) and productive efficiency (minimum ATC) in the long run. A monopoly typically restricts output, charges a higher price, and creates deadweight loss, though it may benefit from economies of scale and innovation.
在完全竞争中，企业在长期实现配置效率 (P = MC) 和生产效率 (最低 ATC)。垄断通常会限制产出、收取更高价格并造成无谓损失，但也可能因规模经济和创新而受益。
5. Market Failure | 市场失灵
Market failure occurs when the free market fails to allocate resources efficiently. Key types include externalities, public goods, and information asymmetry.
市场失灵是指自由市场未能有效配置资源。主要类型包括外部性、公共物品和信息不对称。
Negative production externalities (e.g., pollution) cause overproduction because private costs are lower than social costs. A Pigouvian tax can internalise the externality.
负生产外部性（如污染）导致过度生产，因为私人成本低于社会成本。庇古税可以将外部性内部化。
Positive consumption externalities (e.g., vaccination) lead to underconsumption. A subsidy can encourage socially optimal output.
正消费外部性（如疫苗接种）导致消费不足。补贴可以鼓励达到社会最优产出。
Public goods are non-rivalrous and non-excludable, leading to the free-rider problem. Governments often provide them directly.
公共物品具有非竞争性和非排他性，导致“搭便车”问题。政府通常直接提供这些物品。
Information asymmetry, such as adverse selection and moral hazard, can also cause market failure and may require regulation.
信息不对称，如逆向选择和道德风险，也会导致市场失灵，可能需要监管。
6. Macroeconomic Indicators | 宏观经济指标
Gross Domestic Product (GDP) measures the total value of final goods and services produced within a country in a given period. Real GDP adjusts for inflation and is a key indicator of economic growth.
国内生产总值 (GDP) 衡量一个国家在特定时期内生产的最终商品和服务的总价值。实际 GDP 剔除了通胀影响，是经济增长的关键指标。
ur force) × 100. Types include cyclical, structural, frictional and seasonal unemployment.
失业率 = (失业人数 ÷ 劳动力) × 100。类型包括周期性、结构性、摩擦性和季节性失业。
Inflation is a sustained increase in the general price level. It is measured by the Consumer Price Index (CPI). Deflation and disinflation are distinct concepts.
通胀是总体价格水平的持续上涨，通过消费者价格指数 (CPI) 衡量。通货紧缩与通胀放缓是不同的概念。
The balance of payments records a country's transactions with the rest of the world, comprising the current account, capital account and financial account.
国际收支平衡表记录了一国与世界其他地区的交易，包括经常账户、资本账户和金融账户。
7. Aggregate Demand and Aggregate Supply | 总需求与总供给
is downward sloping due to the wealth effect, interest rate effect and net export effect.
总需求 (AD) 是对国内商品和服务的总支出。AD = C + I + G + (X - M)。由于财富效应、利率效应和净出口效应，AD 曲线向下倾斜。
Short-run aggregate supply (SRAS) is upward sloping because input prices are sticky. LRAS is vertical at the full employment level of output (potential GDP).
短期总供给 (SRAS) 向上倾斜，因为投入价格具有粘性。长期总供给 (LRAS) 在充分就业产出水平（潜在 GDP）处垂直。
Shifts in AD can be caused by changes in consumer confidence, fiscal policy, monetary policy, or foreign incomes. SRAS shifts due to changes in input costs, supply shocks, or business taxes.
AD 的移动可能由消费者信心、财政政策、货币政策或国外收入的变化引起。SRAS 因投入成本、供给冲击或企业税的变化而移动。
An inflationary gap occurs when AD exceeds LRAS, causing demand-pull inflation. A deflationary gap arises when AD is below LRAS, leading to cyclical unemployment.
当 AD 超过 LRAS 时出现通胀缺口，引发需求拉动型通胀。当 AD 低于 LRAS 时出现紧缩缺口，导致周期性失业。
8. Fiscal and Monetary Policy | 财政与货币政策
Fiscal policy involves government spending and taxation. Expansionary fiscal policy (↑G or ↓T) boosts AD, while contractionary policy cools an overheating economy.
财政政策涉及政府支出和税收。扩张性财政政策（增加 G 或减少 T）刺激 AD，紧缩性政策为过热经济降温。
Monetary policy, conducted by the central bank, influences the money supply and interest rates. Lowering interest rates increases consumption and investment, shifting AD right.
由中央银行执行的货币政策影响货币供应和利率。降低利率会增加消费和投资，使 AD 右移。
Supply-side policies aim to increase LRAS by improving productivity, such as investment in education, infrastructure, and deregulation. These policies can achieve non-inflationary growth.
供给方政策旨在通过提高生产率来增加 LRAS，例如教育投资、基础设施建设和放松管制。这些政策可实现无通胀增长。
The multiplier effect means an initial change in spending leads to a larger final change in national income. The formula is:
乘数效应意味着一笔初始支出的变动会导致国民收入更大规模的最终变动。公式为：
Multiplier = 1 ÷ (1 - MPC)
Where MPC is the marginal propensity to consume.
其中 MPC 为边际消费倾向。
9. International Trade and Exchange Rates | 国际贸易与汇率
Comparative advantage explains why countries benefit from trade even if one country has an absolute advantage in all goods. Specialisation and trade increase global output.
比较优势解释了为何即使一个国家在所有商品上都具有绝对优势，仍能从贸易中获益。专业化和贸易能增加全球产出。
Trade protectionism includes tariffs, quotas, and subsidies to domestic producers. While they may protect jobs, they typically raise prices and create deadweight loss.
贸易保护主义包括关税、配额和对国内生产者的补贴。虽然可能保护就业，但通常会推高价格并造成无谓损失。
Exchange rate regimes can be floating, fixed, or managed. A depreciation makes exports cheaper and imports dearer, improving the trade balance in the long run if the Marshall-Lerner condition holds.
汇率制度可以是浮动、固定或有管理的。贬值使出口更便宜、进口更昂贵，若满足马歇尔-勒纳条件，长期内会改善贸易平衡。
The current account balance includes trade in goods and services, primary income and secondary income. A persistent deficit may indicate a lack of competitiveness.
经常账户余额包括商品和服务贸易、初次收入和二次收入。持续的赤字可能表明缺乏竞争力。
10. Economic Development | 经济发展
Economic growth refers to an increase in real GDP, while economic development is a broader concept encompassing improvements in health, education, and living standards, often measured by the Human Development Index (HDI).
经济增长指实际 GDP 的增加，而经济发展是一个更广泛的概念，涵盖健康、教育和生活水平的提升，通常用人类发展指数 (HDI) 衡量。
Barriers to development include low savings, inadequate infrastructure, corruption, political instability, and protectionist policies in developed countries.
发展的障碍包括低储蓄、基础设施不足、腐败、政治不稳定以及发达国家的保护主义政策。
Strategies for development range from trade liberalisation and foreign direct investment to microfinance and aid. Market-based approaches are often complemented by interventionist policies.
发展策略包括贸易自由化、外国直接投资、小额信贷和援助。以市场为导向的策略往往与干预性政策相辅相成。
11. Exam Technique: Data Response | 考试技巧：数据回应题
For Part (a) definitions, be precise and use economic terminology. Provide a real-world example where appropriate.
对于 part (a) 的定义题，要精确并使用经济学术语。适当提供现实例子。
Part (b) usually requires a diagram. Draw it clearly, label axes and curves, and show the shifts or equilibria. Refer to the data provided.
part (b) 通常要求画图。画图要清晰，标明坐标轴和曲线，展示移动或均衡。引用所给数据。
For the evaluative Part (c) or (d), follow the DEED structure: Define key terms, Explain the theory, provide an Example from the text, and use a Diagram. Then evaluate with CLASPP.
对于评估性的 part (c) 或 (d)，遵循 DEED 结构：定义关键词，解释理论，引用文中例子，并使用图表。然后用 CLASPP 进行评估。
12. Exam Technique: Essay Evaluation | 考试技巧：论文评估
High-scoring essays include substantial evaluation. Use CLASPP: Conclusion (answer the question), Long-run vs short-run effects, Assumptions made in the theory, Stakeholders affected, Priorities of government, and Pros and cons of policies.
高分论文包含实质评估。使用 CLASPP：结论（回答问题）、长期与短期效应、理论中的假设、受影响的利益相关者、政府的优先顺序以及政策的利弊。
Always consider the limitations of the model. For instance, the AD/AS model assumes ceteris paribus and does not capture behavioural complexities.
始终考虑模型的局限性。例如，AD/AS 模型假定其他条件不变，无法捕捉行为复杂性。
Integrate real-world examples from your own knowledge. Mentioning specific countries or recent events strengthens your argument and shows depth.
融入自己的知识中的现实案例。提及具体国家或近期事件能加强论证并展现深度。
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