IB & CCEA Economics: Last-Minute Revision Notes | IB与CCEA经济：考前冲刺笔记

📚 IB & CCEA Economics: Last-Minute Revision Notes | IB与CCEA经济：考前冲刺笔记

As the final assessment approaches, a structured and focused revision of core economic principles can make all the difference. This set of notes distils essential topics for IB and CCEA Economics, covering micro and macro concepts, market structures, international trade, and key diagrams. Whether you are reviewing for Paper 1 essays or data-response questions, use this guide to reinforce your understanding and exam technique.

随着最终考试的临近，有条理、抓重点地复习经济学核心原理可以产生决定性的影响。这份笔记浓缩了IB和CCEA经济学的核心主题，涵盖微观与宏观概念、市场结构、国际贸易以及关键图表。无论你是在备考论文卷一还是数据分析题，都可以用这份指南巩固理解和应试技巧。

1. Scarcity and Choice | 稀缺性与选择

The fundamental economic problem is scarcity: unlimited wants but limited resources. This forces individuals, firms, and governments to make choices, incurring opportunity cost — the value of the next best alternative forgone. The production possibility curve (PPC) illustrates these trade-offs, showing attainable combinations of two goods and the concept of increasing opportunity cost when the curve is concave.

根本的经济问题是稀缺性：无限的需求与有限的资源。这迫使个人、企业和政府做出选择，从而产生机会成本——即所放弃的次优选项的价值。生产可能性曲线（PPC）展示了这些权衡，它表示两种商品的可实现组合，并且当曲线凹向原点时体现了机会成本递增的概念。

Opportunity cost = sacrifice / gain
PPC shifts outward with economic growth (more resources or better technology).
Points inside the PPC indicate inefficient use of resources.
机会成本 = 所放弃的 / 所获得的
经济增长（资源增加或技术进步）使PPC向外移动。
PPC内部的点表示资源未得到有效利用。

2. Demand, Supply, and Equilibrium | 需求、供给与均衡

The law of demand states that as price falls, quantity demanded rises, ceteris paribus. The demand curve slopes downward. Supply curves slope upward, reflecting the law of supply. Market equilibrium occurs where quantity demanded equals quantity supplied. Shifts in either curve change the equilibrium price and quantity. Key shift factors include income, tastes, prices of related goods (demand), and costs of production, technology, taxes (supply).

需求定律指出，在其他条件不变的情况下，价格下降则需求量上升。需求曲线向下倾斜。供给曲线向上倾斜，反映了供给定律。市场均衡发生在需求量等于供给量之处。任一曲线的移动都会改变均衡价格和数量。主要的移动因素包括收入、偏好、相关商品价格（需求），以及生产成本、技术、税收（供给）。

Demand shifts right when:	Supply shifts right when:
Income rises (normal good)	Input prices fall
Price of substitute rises	Technology improves
Tastes become favourable	Subsidies increase

需求右移的情况：收入上升（正常品）；替代品价格上升；偏好增强。
供给右移的情况：投入品价格下降；技术进步；补贴增加。

3. Elasticities | 弹性

Price elasticity of demand (PED) measures responsiveness of quantity demanded to a change in price. PED = %ΔQd / %ΔP. If |PED| > 1, demand is elastic; if < 1, inelastic; if = 1, unit elastic. PED influences total revenue: raising price increases revenue when demand is inelastic, but reduces it when elastic. Income elasticity (YED) and cross-price elasticity (XED) are also tested frequently.

需求的价格弹性（PED）衡量需求量对价格变动的反应程度。PED = 需求量变动百分比 / 价格变动百分比。若 |PED| > 1，需求富有弹性；若 < 1，缺乏弹性；若 = 1，单位弹性。PED影响总收入：当需求缺乏弹性时，提价会增加收入；富有弹性时则减少。收入弹性（YED）和交叉价格弹性（XED）也经常考查。

Determinants of PED: substitutes, necessity vs luxury, proportion of income, time.
PED along a linear demand curve varies: elastic at high prices, inelastic at low prices.
YED > 0 normal good; YED < 0 inferior good.
XED > 0 substitutes; XED < 0 complements.
PED的决定因素：替代品、必需品vs奢侈品、支出占比、时间。
线性需求曲线上PED变化：高价位弹性大，低价位弹性小。
YED > 0 正常品；YED < 0 低档品。
XED > 0 替代品；XED < 0 互补品。

4. Government Intervention | 政府干预

Governments intervene to correct market failures or achieve equity. Indirect taxes (specific or ad valorem) shift supply left and raise price. Subsidies shift supply right and lower price. Price controls include maximum prices (ceilings, leading to shortages) and minimum prices (floors, leading to surpluses). Buffer stock schemes and tradable pollution permits are also notable interventions.

政府干预旨在纠正市场失灵或实现公平。间接税（从量税或从价税）使供给曲线左移并提高价格。补贴使供给右移并降低价格。价格管制包括最高限价（价格上限，导致短缺）和最低限价（价格下限，导致过剩）。缓冲库存计划和可交易的污染许可证也是值得注意的干预措施。

Tax incidence depends on relative elasticities: more inelastic side bears more burden.

税收归宿取决于相对弹性：更缺乏弹性的一方承担更多税负。

5. Market Failure and Externalities | 市场失灵与外部性

Market failure occurs when the free market does not achieve allocative efficiency (MSB ≠ MSC). Negative externalities (e.g. pollution) cause overproduction because MSC > MPC. Positive externalities (e.g. education) cause underproduction because MSB > MPB. Public goods (non-rival, non-excludable) suffer from the free-rider problem and are underprovided by the market. Information asymmetry and monopoly power are also market failures.

当自由市场无法实现配置效率（MSB ≠ MSC）时，便出现市场失灵。负外部性（如污染）导致过度生产，因为边际社会成本大于边际私人成本。正外部性（如教育）导致生产不足，因为边际社会收益大于边际私人收益。公共物品（非竞争性、非排他性）存在搭便车问题，市场供给不足。信息不对称和垄断势力也是市场失灵的来源。

Solutions: Pigouvian taxes for negative externalities; subsidies for positive externalities.
Sustainable development: balancing economic growth with environmental protection.
Coase theorem: with low transaction costs and defined property rights, private bargaining can solve externalities.
解决方法：对负外部性征收庇古税；对正外部性给予补贴。
可持续发展：平衡经济增长与环境保护。
科斯定理：在低交易成本且产权界定清晰的条件下，私人谈判可以解决外部性问题。

6. Costs, Revenues, and Profit | 成本、收益与利润

In the short run, firms face fixed and variable costs. Key cost concepts: total cost (TC), average total cost (ATC), and marginal cost (MC). MC intersects ATC and AVC at their minimum points. The law of diminishing returns explains why MC eventually rises. Revenue concepts: total revenue (TR = P × Q), average revenue (AR = TR/Q = demand), marginal revenue (MR). Profit maximisation occurs where MC = MR.

在短期，企业面临固定成本和可变成本。关键成本概念：总成本（TC）、平均总成本（ATC）和边际成本（MC）。MC在ATC和AVC的最低点与之相交。边际报酬递减规律解释了MC最终上升的原因。收益概念：总收益（TR = P × Q）、平均收益（AR = TR/Q = 需求）、边际收益（MR）。利润最大化产出位于MC = MR处。

Normal profit is the minimum return to keep resources in their current use (zero economic profit). Supernormal profit exists when AR > ATC.

正常利润是维持资源原有用途的最低回报（经济利润为零）。当AR > ATC时存在超额利润。

7. Perfect Competition and Monopoly | 完全竞争与垄断

Perfect competition features many buyers and sellers, homogeneous products, perfect information, and no barriers to entry. Firms are price takers. In the long run, only normal profit is earned due to free entry and exit. Allocative efficiency (P = MC) and productive efficiency (at minimum ATC) are achieved in the long run.

完全竞争的特征包括众多买卖者、同质产品、完全信息和无进入壁垒。企业是价格接受者。长期中，由于自由进出，只能获得正常利润。长期可实现配置效率（P = MC）和生产效率（位于最低ATC）。

Monopoly: single seller, high barriers, price maker. A monopolist restricts output and charges a higher price, leading to allocative inefficiency (P > MC) and a deadweight welfare loss. Natural monopoly occurs when economies of scale make a single firm more efficient; regulation may be needed.

垄断：单一卖方，高进入壁垒，价格制定者。垄断者限制产量并索要高价，导致配置无效率（P > MC）和无谓损失。当规模经济使得单一企业更有效率时，便形成自然垄断；可能需要监管。

Price discrimination: charging different prices to different consumers based on willingness to pay, increasing producer surplus.
Monopolistic competition: many firms, differentiated products, some price-setting power, zero long-run economic profit.
Oligopoly: few dominant firms, interdependence, often analysed using game theory and kinked demand curve.
价格歧视：根据支付意愿对不同消费者收取不同价格，增加生产者剩余。
垄断竞争：众多企业、差异化产品、一定定价权，长期经济利润为零。
寡头垄断：少数主导企业，相互依赖，常使用博弈论和弯折需求曲线分析。

8. Macroeconomic Objectives and Indicators | 宏观经济目标与指标

Governments aim for stable economic growth, low unemployment, low and stable inflation, and a sustainable balance of payments. GDP measures the total value of final goods and services produced in a country over a period. Real GDP adjusts for inflation. GDP per capita gives an average income measure, but has limitations as a welfare indicator (ignores inequality, non-market activity, environmental damage).

政府的目标包括稳定的经济增长、低失业、低且稳定的通胀以及可持续的国际收支平衡。GDP衡量一国在一定时期内生产的最终商品与服务的总价值。实际GDP剔除了通胀影响。人均GDP给出了平均收入度量，但作为福利指标存在局限性（忽略不平等、非市场活动、环境破坏）。

Inflation measured by CPI (Consumer Price Index). Causes: demand-pull and cost-push.
Unemployment types: cyclical, structural, frictional, seasonal.
Balance of payments: current account (trade in goods, services, income, transfers) and capital/financial account.
通胀用CPI（消费者价格指数）衡量。成因：需求拉动型和成本推动型。
失业类型：周期性、结构性、摩擦性、季节性。
国际收支：经常账户（货物、服务、收入、转移）和资本/金融账户。

9. Aggregate Demand and Aggregate Supply | 总需求与总供给

Aggregate demand (AD) = C + I + G + (X – M). AD curve slopes downward due to wealth effect, interest rate effect, and net export effect. Short-run aggregate supply (SRAS) shows the relationship between price level and real output when at least one factor price is fixed. Long-run aggregate supply (LRAS) is vertical at the full-employment level of output (potential GDP). Shifts in LRAS come from changes in quantity or quality of resources.

总需求（AD）= 消费 + 投资 + 政府支出 +（出口 – 进口）。AD曲线向下倾斜是因为财富效应、利率效应和净出口效应。短期总供给（SRAS）描绘了至少一种要素价格固定时价格水平与实际产出之间的关系。长期总供给（LRAS）在充分就业产出水平（潜在GDP）处垂直。LRAS的移动源于资源数量或质量的变化。

Keynesian AS curve is horizontal at low output levels, then upward-sloping, becoming vertical at full employment. Classical/monetarist view assumes flexible prices and wages, so economy self-corrects to full employment.

凯恩斯主义总供给曲线在低产出水平处水平，随后向上倾斜，达到充分就业时垂直。古典/货币主义观点假设价格和工资具有弹性，因此经济会自动调整到充分就业。

10. Fiscal and Monetary Policy | 财政政策与货币政策

Fiscal policy involves changes in government spending and taxation to influence AD. Expansionary fiscal policy (higher G, lower T) boosts AD, used during recessions. Contractionary fiscal policy cools an overheating economy. Automatic stabilisers (progressive taxes, unemployment benefits) work without active decisions. Fiscal policy can be limited by time lags, crowding out, and government debt concerns.

财政政策涉及改变政府支出和税收以影响AD。扩张性财政政策（增加G、降低T）刺激AD，用于衰退时期。紧缩性财政政策为过热经济降温。自动稳定器（累进税、失业救济金）无需主动决策即可发挥作用。财政政策可能受到时滞、挤出效应及政府债务问题的制约。

Monetary policy, usually controlled by a central bank, uses interest rates, money supply, and credit controls to achieve price stability and support growth. Lower interest rates stimulate investment and consumption. Quantitative easing (QE) is an unconventional tool that injects liquidity by purchasing assets. The transmission mechanism links policy rate changes to AD through various channels.

货币政策通常由中央银行掌控，运用利率、货币供给和信贷控制来实现物价稳定并支持增长。降低利率可刺激投资和消费。量化宽松（QE）是一种非常规工具，通过购买资产注入流动性。传导机制通过多种渠道将政策利率变动与AD联系起来。

Policy goal	Expansionary action
Boost AD	Lower interest rate / Increase G
Reduce inflation	Raise interest rate / Cut G

政策目标：提振AD → 降低利率 / 增加G；降低通胀 → 提高利率 / 削减G。

11. International Trade and Exchange Rates | 国际贸易与汇率

Comparative advantage explains trade based on lowest opportunity cost. Free trade brings gains: increased choice, lower prices, efficiency from specialisation. Protectionist measures (tariffs, quotas, subsidies) shield domestic industries but create deadweight loss. Exchange rate systems: floating, fixed, and managed. A weaker currency makes exports cheaper and imports dearer, improving the trade balance if Marshall-Lerner condition holds.

比较优势以最低机会成本解释贸易。自由贸易带来好处：选择增多、价格降低、专业化带来效率提升。保护主义措施（关税、配额、补贴）保护国内产业，但造成无谓损失。汇率制度：浮动汇率、固定汇率和有管理的汇率。本币贬值使出口更便宜而进口更昂贵，若满足马歇尔-勒纳条件，将改善贸易差额。

Balance of payments must always balance: current account deficit = capital/financial account surplus.

国际收支始终平衡：经常账户赤字 = 资本/金融账户盈余。

12. Development Economics | 发展经济学

Economic development goes beyond GDP growth; it encompasses health, education, and freedom. Barriers include low savings, poor infrastructure, corruption, and resource dependency. Strategies: trade liberalisation, microfinance, foreign direct investment, and ODA (official development assistance). Sustainable Development Goals (SDGs) provide a global framework. The Lewis model explains structural transformation from subsistence agriculture to modern industry.

经济发展超越GDP增长，涵盖健康、教育及自由。障碍包括低储蓄、基础设施薄弱、腐败和资源依赖。发展战略：贸易自由化、小额信贷、外国直接投资以及官方发展援助（ODA）。可持续发展目标（SDGs）提供了全球框架。刘易斯模型解释了从自给农业向现代工业的结构转型。

Human Development Index (HDI): composite of life expectancy, education, and GNI per capita.
Harrod-Domar model emphasises the role of savings and capital-output ratio in growth.
Microcredit empowers small entrepreneurs, especially women, in low-income economies.
人类发展指数（HDI）：由预期寿命、教育和人均GNI合成的指标。
哈罗德-多马模型强调储蓄和资本产出比在增长中的作用。
小额贷款赋予低收入经济中的小企业家（尤其是女性）力量。

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IB & CCEA Economics: Last-Minute Revision Notes | IB与CCEA经济：考前冲刺笔记