📚 IB & CIE Economics: Last-Minute Revision Notes | IB CIE 经济：考前冲刺笔记
These concise revision notes cover the essential concepts, diagrams, and evaluation points you need for the IB and CIE Economics examinations. From scarcity and elasticity to fiscal policy and international trade, each section pairs key theory with exam-ready insights. Use this as your final checklist before entering the exam hall.
这份精简的考前冲刺笔记涵盖了 IB 与 CIE 经济考试必备的核心概念、图示和评估要点。从稀缺性、弹性到财政政策和国际贸易，每一节都将关键理论与应试洞察配对呈现。请在走进考场前将这份清单作为最后的复习依据。
1. Microeconomics Foundations: Scarcity & Choice | 微观基础：稀缺性与选择
The fundamental economic problem is scarcity: unlimited wants but limited resources. Because resources are finite, every society must answer three basic questions: what to produce, how to produce, and for whom to produce. The production possibility curve (PPC) illustrates opportunity cost, trade-offs, and economic growth. A shift outward of the PPC represents an increase in an economy’s productive capacity, often driven by better technology or an increase in factor resources.
经济学的基本问题是稀缺性：无限欲望与有限资源之间的矛盾。由于资源有限，每个社会都必须回答三个基本问题：生产什么、如何生产以及为谁生产。生产可能性曲线（PPC）展示了机会成本、权衡取舍和经济增长。PPC 向外移动表示经济体生产能力的提高，通常由技术进步或要素资源增加驱动。
Opportunity cost is the value of the next best alternative forgone. On a concave PPC, opportunity cost increases as resources are not perfectly adaptable. In a straight-line PPC, opportunity cost remains constant. Free goods are abundant and have zero opportunity cost, while economic goods are scarce and carry an opportunity cost. Rational decision-making at the margin involves comparing marginal benefits with marginal costs.
机会成本是所放弃的次优选择的价值。在凹向原点的 PPC 上，由于资源并非完全可转移，机会成本递增。而在直线 PPC 上机会成本不变。免费物品充裕且机会成本为零，经济物品稀缺且有机会成本。理性的边际决策要求比较边际收益与边际成本。
2. Demand, Supply & Market Equilibrium | 需求、供给与市场均衡
The law of demand states that, ceteris paribus, as price rises, quantity demanded falls. Demand can shift due to changes in income, tastes, prices of substitutes or complements, and expectations. The law of supply states that as price rises, quantity supplied increases. Supply shifts are caused by changes in production costs, technology, taxes, subsidies, and weather conditions.
需求定律指出，在其他条件不变时，价格上升则需求量下降。需求可因收入、偏好、替代品或互补品价格以及预期变化而移动。供给定律指出，价格上升则供给量增加。供给移动由生产成本、技术、税收、补贴以及天气条件等因素变化引起。
Market equilibrium occurs where demand equals supply, determining price and quantity. A shortage (excess demand) pushes price up; a surplus (excess supply) pushes price down. The price mechanism performs a signalling and incentive function, allocating resources efficiently in competitive markets. Both consumer surplus and producer surplus are maximised at the free-market equilibrium, indicating allocative efficiency where price equals marginal cost.
市场均衡在需求等于供给时实现，决定价格与数量。短缺（超额需求）推动价格上升；过剩（超额供给）推动价格下降。价格机制发挥信号与激励功能，在竞争性市场中有效配置资源。在自由市场均衡处，消费者剩余与生产者剩余均达到最大，表明价格等于边际成本时实现了配置效率。
3. Elasticities: PED, PES, YED, XED | 弹性：需求价格弹性等
Price elasticity of demand (PED) measures responsiveness of quantity demanded to a change in price. PED = %ΔQd / %ΔP. Demand is elastic when |PED| > 1, inelastic when |PED| < 1, and unit elastic when |PED| = 1. PED is a key determinant of the effect of a price change on total revenue: if demand is elastic, a price cut raises total revenue; if inelastic, a price increase raises total revenue.
需求价格弹性（PED）衡量需求量对价格变化的反应程度。PED = 需求量变动百分比 / 价格变动百分比。当 |PED| > 1 时需求富有弹性，|PED| < 1 时缺乏弹性，|PED| = 1 时为单位弹性。PED 是价格变动对总收益影响的关键决定因素：若需求富有弹性，降价会提高总收益；若缺乏弹性，提价会提高总收益。
Price elasticity of supply (PES) measures responsiveness of quantity supplied to price. PES = %ΔQs / %ΔP. Supply is more elastic when firms can increase output quickly and easily, influenced by the time period and the availability of spare capacity. Income elasticity of demand (YED) helps classify goods as normal (YED > 0) or inferior (YED < 0). Cross elasticity of demand (XED) indicates whether goods are substitutes (XED > 0) or complements (XED < 0).
供给价格弹性（PES）衡量供给量对价格的敏感度。PES = 供给量变动百分比 / 价格变动百分比。当企业能迅速轻松地提高产出时供给弹性较大，这受时间周期和闲置产能影响。需求收入弹性（YED）用于区分正常品（YED > 0）与劣等品（YED < 0）。需求交叉弹性（XED）表明商品是替代品（XED > 0）还是互补品（XED < 0）。
4. Government Intervention: Taxes, Subsidies & Price Controls | 政府干预：税收、补贴与价格管制
Indirect taxes can be specific (a fixed amount per unit) or ad valorem (a percentage of price). A tax shifts the supply curve leftwards, raising consumer price and reducing quantity. The incidence of tax depends on relative elasticities: when demand is more inelastic than supply, consumers bear a greater tax burden. Taxes can be used to correct negative externalities and raise government revenue.
间接税可分为从量税（每单位固定金额）和从价税（价格的百分比）。税收使供给曲线左移，提高消费者支付的价格并减少数量。税负分摊取决于相对弹性：当需求比供给更缺乏弹性时，消费者承担更多税负。税收可用于纠正负外部性并增加政府收入。
Subsidies shift the supply curve rightwards, lowering price and increasing quantity. They are often justified to encourage merit goods or protect domestic industries. Maximum prices (price ceilings) set below equilibrium create shortages; minimum prices (price floors) set above equilibrium create surpluses. Buffer stock schemes attempt to stabilise prices through government purchases and sales, but are costly and can be difficult to manage.
补贴使供给曲线右移，降低价格并增加数量。补贴常用于鼓励优效品或保护国内产业。最高限价（价格上限）设在均衡之下会造成短缺；最低限价（价格下限）设在均衡之上会造成过剩。缓冲库存计划试图通过政府买卖来稳定价格，但成本高昂且难以管理。
5. Market Failure & Externalities | 市场失灵与外部性
Market failure occurs when the free market fails to allocate resources efficiently. Externalities are spillover effects on third parties not reflected in market prices. A negative externality of production (e.g., pollution) leads to overproduction because private cost is below social cost. A positive externality of consumption (e.g., vaccination) leads to underconsumption because private benefit is below social benefit.
当自由市场无法有效配置资源时便出现市场失灵。外部性是对第三方产生的、未被市场价格反映的溢出效应。生产的负外部性（如污染）导致生产过度，因为私人成本低于社会成本。消费的正外部性（如疫苗接种）导致消费不足，因为私人收益低于社会收益。
Government responses include Pigouvian taxes to internalise external costs, tradable permits, regulation, and direct provision of public goods. Public goods are non-rivalrous and non-excludable, leading to the free-rider problem and market failure. Common access resources are rivalrous but non-excludable, which can result in the tragedy of the commons. Well-designed government intervention can improve social welfare, but government failure may arise due to imperfect information, bureaucracy, or unintended consequences.
政府应对措施包括用庇古税内部化外部成本、排污权交易、管制以及直接提供公共品。公共品具有非竞争性和非排他性，导致搭便车问题与市场失灵。共有资源具有竞争性但非排他性，可能引发公地悲剧。设计得当的政府干预可改善社会福利，但政府失灵也可能由于信息不完全、官僚主义或意外后果而出现。
6. Theory of the Firm & Market Structures | 厂商理论及市场结构
Perfect competition is characterised by many small firms, homogeneous products, perfect information, and no barriers to entry. Firms are price takers. In the short run, supernormal profits can exist, but in the long run, only normal profits are earned at the lowest point of the ATC curve, achieving both productive and allocative efficiency.
完全竞争的特征包括大量小厂商、同质化产品、完全信息和无进入壁垒。厂商是价格接受者。短期可能存在超额利润，但长期仅在平均总成本最低点获得正常利润，同时实现生产效率和配置效率。
Monopoly is a single seller with high barriers to entry. A monopolist is a price maker, setting output where MR = MC and reading price from the demand curve. This leads to higher price, lower output, and a deadweight loss relative to perfect competition. Monopolies can arise from natural cost advantages, legal protection, or control of key resources. They may benefit from economies of scale but suffer from X-inefficiency and lack of innovation incentives.
垄断是单一卖方且存在高进入壁垒。垄断者是价格制定者，在 MR = MC 处确定产量，并从需求曲线读取价格。与完全竞争相比，这导致更高价格、更低产量和无谓损失。垄断可源于自然成本优势、法律保护或对关键资源的控制。它们可能因规模经济得益，但也存在 X-低效率和缺乏创新激励的问题。
7. Macroeconomic Objectives & Indicators | 宏观经济目标与指标
Governments typically pursue four macroeconomic objectives: low and stable inflation, low unemployment, sustainable economic growth, and a favourable balance of payments. Inflation is measured by the consumer price index (CPI), while unemployment is measured by the labour force survey. GDP measures the total value of output produced within an economy over a period; real GDP adjusts for inflation.
政府通常追求四大宏观经济目标：低且稳定的通胀、低失业率、可持续的经济增长以及国际收支平衡。通胀通过消费者物价指数（CPI）衡量，失业通过劳动力调查衡量。GDP 衡量一段时期内经济体内部产出的总价值；实际 GDP 已剔除通胀影响。
The business cycle shows fluctuations in economic activity over time, with phases of boom, recession, trough, and recovery. A negative output gap means actual GDP is below potential, while a positive output gap means the economy is overheating. Indicators such as consumer confidence and business investment help forecast turning points. Sustainable growth requires balancing current output expansion with resource conservation for future generations.
经济周期显示经济活动随时间的波动，经历繁荣、衰退、谷底和复苏阶段。负产出缺口意味着实际 GDP 低于潜在水平，而正产出缺口表明经济过热。消费者信心和商业投资等指标有助于预测拐点。可持续增长要求在扩大当前产出与为后代保留资源之间取得平衡。
8. Aggregate Demand & Aggregate Supply (AD-AS) | 总需求与总供给
Aggregate demand (AD) is the total spending on domestic goods and services at a given price level. AD = C + I + G + (X – M). A fall in the price level increases real wealth, lowers interest rates, and improves international competitiveness, causing a movement along the AD curve. AD can shift due to changes in consumer confidence, monetary policy, fiscal policy, or external demand.
总需求（AD）是在既定价格水平下对国内商品和服务的总支出。AD = 消费 + 投资 + 政府支出 + 净出口。价格水平下降会增加实际财富、降低利率并提升国际竞争力，导致沿 AD 曲线移动。AD 可因消费者信心、货币政策、财政政策或外部需求变化而移动。
Short-run aggregate supply (SRAS) slopes upward because, at least temporarily, higher prices encourage firms to expand output. SRAS shifts with changes in input prices, taxes, or supply shocks. Long-run aggregate supply (LRAS) is vertical at the full-employment level of output, representing an economy’s potential GDP. LRAS can increase through improved labour productivity, investment, technological progress, and institutional reforms.
短期总供给曲线向上倾斜，因为至少在短期内较高价格激励企业扩大产出。SRAS 随投入品价格、税收或供给冲击变化而移动。长期总供给（LRAS）在充分就业产出水平上呈垂直线，代表经济体的潜在 GDP。LRAS 可通过劳动生产率提高、投资、技术进步和制度改革而增加。
9. Fiscal Policy & Monetary Policy | 财政政策与货币政策
Fiscal policy involves government spending and taxation. Expansionary fiscal policy (higher spending, lower taxes) boosts AD and can reduce cyclical unemployment, but may increase government debt and crowd out private investment. Contractionary fiscal policy (lower spending, higher taxes) cools an overheating economy. Automatic stabilisers, such as progressive taxes and welfare benefits, mitigate fluctuations without active policy changes.
财政政策涉及政府支出与税收。扩张性财政政策（更高支出、更低税收）刺激 AD 并可降低周期性失业，但可能增加政府债务并挤出私人投资。紧缩性财政政策（更低支出、更高税收）给过热经济降温。自动稳定器，如累进税和福利金，无需主动政策变化即可缓和波动。
Monetary policy is conducted by central banks, primarily through interest rates and quantitative easing. Lower interest rates reduce the cost of borrowing and the reward for saving, stimulating consumption and investment. Higher interest rates do the opposite. Inflation targeting (commonly 2%) helps anchor expectations. In a liquidity trap, monetary policy may become ineffective, requiring fiscal policy to restore growth. Evaluation must consider time lags, effectiveness in deep recessions, and the independence of the central bank.
货币政策由中央银行执行，主要通过利率和量化宽松。较低利率降低借贷成本和储蓄收益，刺激消费与投资。较高利率则相反。通胀目标制（通常为 2%）有助于锚定预期。在流动性陷阱中，货币政策可能失效，需财政政策恢复增长。评估需考虑时滞、在深度衰退中的有效性以及央行的独立性。
10. International Trade & Exchange Rates | 国际贸易与汇率
The theory of comparative advantage shows that countries benefit from specialisation and trade even if one is absolutely more efficient in producing all goods. Free trade increases consumer choice, lowers prices, and promotes efficiency. Protectionist measures, such as tariffs, quotas, and subsidies, can protect infant industries or preserve jobs but typically raise prices and create a deadweight loss.
比较优势理论表明，即使一国在所有商品生产中都具有绝对优势，各国仍能从专业化和贸易中获益。自由贸易增加消费者选择、降低价格并促进效率。保护主义措施，如关税、配额和补贴，可保护幼稚产业或保留就业，但通常推高价格并造成无谓损失。
Exchange rates can be floating, fixed, or managed. A depreciation makes exports cheaper and imports dearer, improving the current account if the Marshall-Lerner condition holds, though the J-curve effect may cause an initial worsening. Currency appreciation has the opposite effect. Central banks intervene in foreign exchange markets or adjust interest rates to influence exchange rates. A strong currency helps control inflation but hurts export competitiveness.
汇率制度可以是浮动、固定或有管理的。货币贬值使出口更便宜、进口更昂贵，若马歇尔-勒纳条件成立则可改善经常账户，但 J 曲线效应可能导致初期恶化。货币升值效果相反。中央银行通过干预外汇市场或调整利率来影响汇率。强势货币有助于控制通胀，但损害出口竞争力。
11. Economic Development & Growth | 经济发展与增长
Economic growth, measured by rising real GDP, is necessary but not sufficient for economic development. Development encompasses improved living standards, healthcare, education, and reduced poverty. The Human Development Index (HDI) combines income, life expectancy, and education into a broader measure. Barriers to development include inadequate infrastructure, corruption, political instability, and limited access to credit.
以实际 GDP 衡量的经济增长是经济发展的必要条件，但并非充分条件。发展涵盖改善的生活水准、医疗、教育和减贫。人类发展指数（HDI）将收入、预期寿命和教育综合为一个更广泛的指标。发展障碍包括基础设施不足、腐败、政治不稳定以及信贷获取受限。
Growth strategies include market-oriented approaches such as trade liberalisation and privatisation, as well as interventionist approaches like infrastructure investment and social safety nets. Sustainable Development Goals (SDGs) provide a global framework for development. A key evaluation point is that growth may increase inequalities or cause environmental damage unless carefully managed, hence the need for inclusive and green growth.
增长策略包括以市场为导向的方法，如贸易自由化和私有化，以及干预主义方法，如基础设施投资和社会安全网。可持续发展目标（SDGs）为发展提供了全球框架。一个关键的评估要点是，除非谨慎管理，增长可能加剧不平等或导致环境破坏，因此需要包容性和绿色增长。
12. Exam Technique & Key Diagrams | 考试技巧与关键图表
In both IB and CIE Economics, mastery of diagrams is essential. Always label axes fully: Price and Quantity, Price Level and Real GDP, or Exchange Rate and Quantity of Currency. Use arrows to show shifts and new equilibrium points. Accompany every diagram with a written explanation. Definitions should be precise and from the syllabus; aim for the two-mark definition style.
在 IB 和 CIE 经济考试中，熟练运用图表至关重要。务必完整标注坐标轴：价格与数量、价格水平与实际 GDP，或汇率与货币数量。使用箭头标出移动及新均衡点。每个图表都需配以文字说明。定义应精确且来自考纲；力求达到两分定义的标准。
For evaluation, go beyond one-sided arguments. Use phrases like ‘It depends on…’, ‘In the short run… but in the long run…’, and ‘The extent of this effect depends on the magnitude of…’. Prioritise policies that address root causes rather than symptoms. When analysing data response questions, always refer to the extract and quote figures or trends. Manage your time strictly: roughly one minute per mark.
进行评估时，要超越单方面的论证。使用诸如“这取决于……”、“短期……但长期……”以及“这一效应的程度取决于……的大小”等表达。优先考虑解决根本原因而非症状的政策。在分析数据回应题时，始终引用材料并提及数据或趋势。严格管理时间：大致每分题一分钟。
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