📚 AS Edexcel Economics: Core Knowledge Summary | AS Edexcel 经济：核心知识点梳理
This article provides a structured revision guide for students taking AS Edexcel Economics, covering the core microeconomic and macroeconomic concepts in Themes 1 and 2. Each section pairs English explanations with Chinese equivalents, helping you consolidate key definitions, diagrams, and applications.
本文为准备 AS Edexcel 经济学的同学提供结构化的复习指南，涵盖 Theme 1 和 Theme 2 的核心微观与宏观经济概念。每个部分均以中英双语对照讲解，帮助你巩固关键定义、图表和应用。
1. The Basic Economic Problem | 基本经济问题
The basic economic problem is scarcity – the idea that finite resources cannot satisfy infinite wants. This forces all economies to answer three fundamental questions: what to produce, how to produce, and for whom to produce.
基本经济问题是稀缺性——有限的资源无法满足无限的欲望。这迫使所有经济体回答三个基本问题：生产什么、如何生产、为谁生产。
Opportunity cost measures the cost of the next best alternative forgone. Economic agents – consumers, firms, and governments – face trade-offs in every decision. For example, a government that spends more on healthcare may have to reduce spending on education.
机会成本衡量所放弃的下一个最优选择的价值。经济主体（消费者、企业和政府）在每一个决策中都面临权衡取舍。例如，政府若增加医疗支出，就可能需要减少教育支出。
Production possibility frontiers (PPFs) illustrate scarcity, choice, and opportunity cost. A movement along the PPF shows an opportunity cost; a shift outward represents economic growth.
生产可能性边界（PPF）展示了稀缺性、选择和机会成本。沿着 PPF 移动显示了机会成本；向外平移代表经济增长。
2. Demand, Supply and Market Equilibrium | 需求、供给与市场均衡
The law of demand states that, ceteris paribus, quantity demanded falls as price rises. This inverse relationship is shown by a downward-sloping demand curve. Movements along the curve are caused by price changes, while shifts occur due to non-price factors such as income, tastes, or the prices of related goods.
需求定律指出，在其他条件不变的前提下，价格上升会导致需求量下降。这种反向关系表现为向下倾斜的需求曲线。价格变动导致沿着曲线移动，而收入、偏好或相关商品价格等非价格因素则引起曲线平移。
The law of supply says that, ceteris paribus, quantity supplied rises when price rises. The upward-sloping supply curve shifts when input costs, technology, taxes, or subsidies change.
供给定律指出，在其他条件不变的前提下，价格上升会导致供给量增加。向上倾斜的供给曲线会因投入成本、技术、税收或补贴的变化而平移。
Market equilibrium occurs where quantity demanded equals quantity supplied, giving the equilibrium price and quantity. Excess demand pushes prices up; excess supply pushes prices down. This is the price mechanism, which performs a rationing, signalling, and incentive function.
市场均衡出现在需求量等于供给量之处，决定了均衡价格和数量。超额需求推高价格，超额供给压低价格。这就是价格机制，它发挥着配给、信号和激励功能。
3. Elasticity | 弹性
Price elasticity of demand (PED) measures the responsiveness of quantity demanded to a change in price. PED = % change in Qd / % change in price. If |PED| > 1, demand is price-elastic; if |PED| < 1, demand is price-inelastic. Elasticity determines the effect on total revenue: raising price when demand is inelastic raises total revenue.
需求的价格弹性（PED）衡量需求量对价格变化的反应程度。PED = 需求量变化百分比 / 价格变化百分比。若 |PED| > 1，需求富有弹性；若 |PED| < 1，需求缺乏弹性。弹性决定了对总收入的影响：当需求缺乏弹性时提价会增加总收入。
Price elasticity of supply (PES) measures the responsiveness of quantity supplied to price changes. PES = % change in Qs / % change in price. It is influenced by time periods, spare capacity, and the availability of stocks.
供给的价格弹性（PES）衡量供给量对价格变化的反应程度。PES = 供给量变化百分比 / 价格变化百分比。它受时期长短、闲置产能和存货可得性的影响。
Income elasticity of demand (YED) indicates whether a good is normal (positive YED) or inferior (negative YED). Cross elasticity of demand (XED) reveals whether goods are substitutes (positive XED) or complements (negative XED). Firms use these elasticities to plan marketing and pricing strategies.
需求的收入弹性（YED）表明商品是正常品（正 YED）还是劣等品（负 YED）。需求的交叉弹性（XED）揭示商品是替代品（正 XED）还是互补品（负 XED）。企业运用这些弹性来规划营销和定价策略。
4. Market Failure: Externalities | 市场失灵：外部性
Market failure occurs when the price mechanism leads to an inefficient allocation of resources, where social welfare is not maximised. Externalities are spillover effects imposed on third parties. Negative externalities (e.g. pollution) cause overproduction because private costs are lower than social costs. Positive externalities (e.g. vaccinations) cause underproduction because private benefits fall short of social benefits.
市场失灵发生于价格机制导致资源配置无效率、社会福利未达到最大化之时。外部性是对第三方强加的溢出效应。负外部性（如污染）导致过度生产，因为私人成本低于社会成本。正外部性（如疫苗接种）导致生产不足，因为私人收益小于社会收益。
Welfare loss is the area of deadweight loss when output diverges from the social optimum. For negative externalities, the welfare loss triangle lies to the right of the optimum quantity; for positive externalities, it is to the left.
福利损失是产出偏离社会最优产量时产生的无谓损失区域。对负外部性而言，福利损失三角形位于最优数量右侧；对正外部性而言，则位于左侧。
Internalising an externality means making the private cost or benefit equal to the social cost or benefit, for instance through taxation for negative externalities or subsidies for positive ones.
外部性的内部化是指使私人成本或收益等于社会成本或收益，例如对负外部性征税或对正外部性提供补贴。
5. Market Failure: Public Goods and Information Gaps | 市场失灵：公共物品与信息不对称
Public goods are non-rivalrous and non-excludable. Because individuals can free-ride, private firms have no incentive to provide them. Street lighting and national defence are classic examples. The free-rider problem leads to complete missing markets for public goods.
公共物品具有非竞争性和非排他性。由于个人可以“搭便车”，私人企业缺乏提供的动力。路灯和国防是典型的例子。搭便车问题导致公共物品市场完全缺失。
Information gaps or asymmetric information occur when one party knows more than the other. This leads to adverse selection (e.g. in insurance) or moral hazard. Consumers may overestimate benefits of demerit goods and underestimate costs; firms may exploit information asymmetries to charge higher prices.
信息鸿沟或信息不对称发生在交易一方比另一方掌握更多信息时。这会引发逆向选择（如保险市场）或道德风险。消费者可能高估有害品的收益、低估其成本；企业可能利用信息不对称来抬高价格。
Governments can correct information gaps by mandating labelling, publishing research, or running public health campaigns, helping consumers make better-informed decisions.
政府可以通过强制标签、发布研究结果或开展公共卫生宣传来纠正信息鸿沟，帮助消费者做出更明智的决策。
6. Government Intervention | 政府干预
Governments intervene in markets to correct market failure and promote equity. Main tools include indirect taxes, subsidies, price controls (maximum and minimum prices), regulation, and information provision.
政府干预市场以纠正市场失灵并促进公平。主要工具有间接税、补贴、价格管制（最高限价和最低限价）、监管与信息提供。
An indirect tax (specific or ad valorem) shifts the supply curve leftwards. It is used to reduce negative externalities. The tax incidence depends on relative elasticities: if demand is inelastic, consumers bear a larger share of the tax; if demand is elastic, producers bear more.
间接税（从量税或从价税）使供给曲线向左平移，用于减少负外部性。税负分担取决于相对弹性：若需求缺乏弹性，消费者承担更大份额；若需求富有弹性，生产者承担更多。
A subsidy shifts the supply curve rightwards, reducing price and increasing quantity. It is effective in encouraging consumption of merit goods, but carries an opportunity cost for the government.
补贴使供给曲线向右平移，降低价格、增加数量。它在鼓励有益品消费方面有效，但会带来政府机会成本。
Maximum prices (ceilings) set below equilibrium create shortages; minimum prices (floors) set above create surpluses. Regulations, such as banning smoking indoors or setting emission standards, directly limit harmful activities.
最高限价（价格上限）定于均衡价格之下会导致短缺；最低限价（价格下限）定于均衡价格之上会引起过剩。法规——如室内禁烟或设定排放标准——直接限制有害活动。
7. Macroeconomic Objectives | 宏观经济目标
The UK government’s main macroeconomic objectives are: stable and sustainable economic growth, low and stable inflation (the Bank of England’s target is 2% CPI), low unemployment, and a sustainable balance of payments. Additional objectives may include reducing income inequality and protecting the environment.
英国政府的主要宏观经济目标是：稳定可持续的经济增长、低而稳定的通胀（英格兰银行目标为 2% CPI）、低失业率，以及可持续的国际收支。其他目标可能包括减少收入不平等和保护环境。
Economic growth is measured by the percentage change in real GDP. It raises living standards but may also generate inflationary pressure and environmental costs.
经济增长以实际 GDP 的百分比变化来衡量。它能提高生活水平，但也可能带来通胀压力和环境的代价。
Unemployment is measured by the Claimant Count and the Labour Force Survey. Types include cyclical, structural, and frictional unemployment. Inflation is measured by CPI and RPI; it erodes purchasing power and distorts economic decisions.
失业通过申领失业金人数和劳动力调查来衡量。类型包括周期性、结构性与摩擦性失业。通胀以 CPI 和 RPI 来衡量；它侵蚀购买力并扭曲经济决策。
The balance of payments records transactions between the UK and the rest of the world. The current account includes trade in goods and services, primary income, and secondary income. A persistent current account deficit may signal competitiveness issues.
国际收支记录英国与世界其他地区的交易。经常账户包括货物和服务贸易、初次收入和二次收入。持续的经常账户赤字可能表明竞争力存在问题。
8. Aggregate Demand and Aggregate Supply | 总需求与总供给
Aggregate demand (AD) is total planned spending in the economy: AD = C + I + G + (X − M). Consumption (C) is influenced by income, wealth, and interest rates. Investment (I) is driven by business confidence, interest rates, and accelerator effects. Net exports (X − M) depend on relative prices and exchange rates.
总需求（AD）是经济中计划支出的总和：AD = C + I + G + (X − M)。消费（C）受收入、财富和利率影响。投资（I）由企业信心、利率和加速效应驱动。净出口（X − M）取决于相对价格和汇率。
The aggregate supply (AS) curve shows the total output firms are willing to produce. In the short run, the SRAS curve slopes upward because input costs such as wages are sticky. Shifts in SRAS come from changes in raw material prices, taxes, or exchange rates.
总供给（AS）曲线显示企业愿意生产的全部产出。在短期，SRAS 曲线向上倾斜，因为工资等投入成本具有粘性。SRAS 的平移源于原材料价格、税收或汇率的变化。
Long-run aggregate supply (LRAS) represents the economy’s potential output. The classical view shows LRAS as vertical at full capacity, while the Keynesian view shows LRAS with a horizontal section when there is spare capacity. Shifts in LRAS occur through improvements in the quantity or quality of factors of production.
长期总供给（LRAS）代表经济的潜在产出。古典观点认为 LRAS 在充分产能处呈垂直状，而凯恩斯观点认为当存在闲置产能时 LRAS 有一段水平区间。LRAS 的平移来自生产要素数量或质量的提升。
9. Economic Growth and the Economic Cycle | 经济增长与经济周期
Actual economic growth is the expansion of real GDP over time; potential growth is the increase in productive capacity. Growth can be driven by higher AD in the short run, or by supply-side improvements such as technological progress and investment in human capital in the long run.
实际经济增长是指实际 GDP 随时间的扩张；潜在增长是指生产能力的提高。增长在短期可由总需求增加推动，在长期则源于技术进步和人力资本投资等供给侧改善。
The economic (business) cycle refers to fluctuations in actual output around the trend rate of growth. Phases include boom, downturn, recession, and recovery. A negative output gap exists when actual GDP is below trend; a positive output gap occurs when it is above.
经济周期（商业周期）指实际产出围绕趋势增长率的波动。阶段包括繁荣、下行、衰退和复苏。当实际 GDP 低于趋势水平时存在负产出缺口；高于趋势时存在正产出缺口。
Governments and central banks use macroeconomic policies to smooth the cycle. Understanding where the economy sits in the cycle helps guide interest rate decisions and fiscal measures.
政府和中央银行运用宏观经济政策来熨平周期。了解经济体处于周期的哪个阶段有助于指导利率决策和财政措施。
10. Macroeconomic Policy | 宏观经济政策
Fiscal policy involves changes in government spending and taxation to influence AD. Expansionary fiscal policy (higher spending or lower taxes) boosts AD; contractionary policy does the opposite. Fiscal policy can also target specific supply-side objectives through infrastructure spending or tax incentives.
财政政策涉及调整政府支出和税收以影响总需求。扩张性财政政策（增加支出或减税）会刺激 AD；紧缩性政策则相反。财政政策还可通过基础设施支出或税收优惠来针对供给侧目标。
Monetary policy is managed by the Bank of England’s Monetary Policy Committee. The main instrument is the base interest rate, which affects borrowing costs and thus consumption and investment. Quantitative easing (QE) is used when interest rates are near zero to inject liquidity directly into the financial system.
货币政策由英格兰银行货币政策委员会执行。主要工具是基准利率，它影响借贷成本进而影响消费和投资。量化宽松（QE）在利率接近零时使用，直接向金融体系注入流动性。
Supply-side policies aim to raise the economy’s productive potential (shifting LRAS rightwards). They include improving education and training, reducing regulation, privatising state-owned firms, and reforming welfare to incentivise work. These policies can have time lags and may conflict with equity objectives.
供给侧政策旨在提高经济的生产潜力（使 LRAS 向右平移）。它们包括改善教育和培训、放松管制、私有化国有企业以及改革福利以激励就业。这些政策可能具有时滞，并可能与社会公平目标冲突。
Successful policy-making often requires a mix of instruments, as no single tool can achieve all objectives simultaneously without trade-offs.
成功的政策往往需要多种工具配合使用，因为单一工具不可能毫无取舍地同时实现所有目标。
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