📚 AS Cambridge Economics: Core Knowledge Breakdown | AS剑桥经济：核心知识点梳理
Welcome to this concise yet comprehensive overview of the AS Cambridge Economics syllabus. The following revision notes distil the most essential micro and macro concepts you must master, from the basic economic problem through to international trade. Each idea is explained in plain English first, followed immediately by its Chinese counterpart, ensuring bilingual clarity for exam preparation.
欢迎阅读这篇简明而全面的 AS 剑桥经济大纲梳理。以下复习笔记提炼了你必须掌握的最核心微观与宏观概念，从基本经济问题一直延伸到国际贸易。每个知识点先用简明英文解释，紧接着配上对应的中文解释，保证双语理解清晰，助力备考。
1. Scarcity, Choice and Opportunity Cost | 稀缺性、选择与机会成本
The fundamental economic problem arises because resources are finite while human wants are unlimited. Scarcity forces individuals, firms and governments to make choices, and every choice involves an opportunity cost – the value of the next best alternative forgone.
基本经济问题源于资源有限而人类欲望无限。稀缺性迫使个人、企业和政府做出选择，而每个选择都涉及机会成本——即所放弃的次优替代品的价值。
The production possibility curve (PPC) illustrates scarcity, choice and opportunity cost. Points on the curve show maximum possible output combinations of two goods with full employment; movement along the curve demonstrates the trade-off and opportunity cost of reallocating resources.
生产可能性曲线（PPC）展示了稀缺性、选择和机会成本。曲线上的点表示在充分就业下两种商品的最大可能产出组合；沿曲线移动体现了重新配置资源时的权衡与机会成本。
2. Demand and Supply Analysis | 需求与供给分析
Demand refers to the quantity of a good consumers are willing and able to purchase at various prices over a given period, ceteris paribus. The law of demand states there is an inverse relationship between price and quantity demanded: as price falls, quantity demanded expands, and vice versa.
需求是指在给定时期内、其他条件不变的情况下，消费者在不同价格水平上愿意且能够购买的商品数量。需求定律指出价格与需求量之间呈反向关系：价格下降，需求量增加，反之亦然。
A change in price causes a movement along the demand curve, while non-price factors – income, tastes, prices of substitutes and complements, expectations – shift the entire demand curve. Similarly, supply depicts producer willingness and ability to sell; its shifts are influenced by costs of production, technology, taxes and subsidies.
价格变动导致沿需求曲线移动，而非价格因素——收入、偏好、替代品与互补品价格、预期——会使整条需求曲线平移。类似地，供给反映生产者的出售意愿与能力；其平移受生产成本、技术、税收和补贴等因素影响。
3. Price Elasticity of Demand and Supply | 需求与供给的价格弹性
Price elasticity of demand (PED) measures the responsiveness of quantity demanded to a change in price. The formula is:
需求的价格弹性（PED）衡量需求量对价格变动的反应程度。计算公式为：
PED = %Δ Quantity Demanded ÷ %Δ Price
When |PED| > 1, demand is elastic and total revenue moves opposite to price. When |PED| < 1, demand is inelastic and total revenue moves with price. Determinants include availability of substitutes, degree of necessity and time period.
当 |PED| > 1，需求富有弹性，总收益与价格反向变动。当 |PED| < 1，需求缺乏弹性，总收益与价格同向变动。决定因素包括替代品的可得性、必需品程度以及时间长短。
Price elasticity of supply (PES) measures how quickly producers can adjust quantity supplied when market price changes. PES depends on production time lags, spare capacity and the storability of goods.
供给的价格弹性（PES）衡量当市场价格变动时生产者调整供给量的速度。PES 取决于生产时滞、剩余产能以及商品的储存难易度。
4. Market Equilibrium and Efficiency | 市场均衡与效率
Market equilibrium occurs where the demand and supply curves intersect, resulting in an equilibrium price and quantity. At this point there is no excess demand or excess supply, and the market clears.
市场均衡出现在需求曲线与供给曲线相交处，形成均衡价格与均衡数量。在该点既无超额需求也无超额供给，市场出清。
Consumer surplus is the difference between what consumers are willing to pay and what they actually pay. Producer surplus is the difference between the market price and the minimum price producers would accept. In a competitive market, total surplus is maximised, indicating allocative efficiency.
消费者剩余是消费者愿意支付的最高价格与实际支付价格之间的差额。生产者剩余是市场价格与生产者愿意接受的最低价格之间的差额。在竞争市场中，总剩余最大化，表明实现了配置效率。
5. Government Intervention in Markets | 政府干预市场
Governments intervene in markets to correct inefficiencies or to achieve equity goals. Common forms include price ceilings (maximum prices) set below equilibrium to protect consumers, and price floors (minimum prices) set above equilibrium to support producers.
政府干预市场是为了纠正效率低下或实现公平目标。常见形式包括设定低于均衡价格的最高限价以保护消费者，以及设定高于均衡价格的最低限价以支持生产者。
Indirect taxes, such as per-unit excises, shift the supply curve leftwards, raising price and reducing quantity. The tax burden is shared between consumers and producers depending on relative elasticities. Subsidies shift supply rightwards, lowering price and increasing quantity.
间接税（如从量税）使供给曲线左移，提高价格并减少数量。税收负担由消费者和生产者根据相对弹性分担。补贴使供给曲线右移，降低价格并增加数量。
6. Externalities and Market Failure | 外部性与市场失灵
Market failure occurs when the free market fails to allocate resources efficiently. A key cause is externalities – spillover effects on third parties. Negative production externalities (e.g., pollution) lead to overproduction because producers ignore external costs; positive consumption externalities (e.g., vaccination) lead to underconsumption.
当自由市场不能有效配置资源时，便出现市场失灵。一个关键原因是外部性——对第三方的溢出效应。负生产外部性（如污染）导致过度生产，因生产者不考虑外部成本；正消费外部性（如疫苗接种）导致消费不足。
Public goods are non-excludable and non-rivalrous, leading to the free-rider problem. Information asymmetry, where one party knows more than another, can cause adverse selection and moral hazard, further contributing to market failure.
公共品具有非排他性和非竞争性，引发搭便车问题。信息不对称（一方比另一方掌握更多信息）可能导致逆向选择和道德风险，进一步加剧市场失灵。
7. Aggregate Demand | 总需求
Aggregate demand (AD) measures the total spending on domestic goods and services at different price levels. The AD curve slopes downward due to the real-balance effect, the interest-rate effect and the international-trade effect.
总需求（AD）衡量在不同价格水平下对国内商品与服务的总支出。由于实际余额效应、利率效应和国际贸易效应，总需求曲线向右下方倾斜。
primarily driven by income, wealth and consumer confidence. Investment (I) depends on business confidence, interest rates and technological progress. Government spending (G) is largely discretionary, while net exports (X-M) respond to foreign income and the exchange rate.
AD = C + I + G + (X − M)。消费（C）主要受收入、财富和消费者信心推动。投资（I）取决于商业信心、利率和技术进步。政府支出（G）主要是斟酌决定的，而净出口（X-M）随国外收入和汇率变化。
8. Aggregate Supply and Macroeconomic Equilibrium | 总供给与宏观经济均衡
Short-run aggregate supply (SRAS) is upward sloping because some input costs are sticky. Changes in costs of raw materials, wages or taxes shift the SRAS curve. Long-run aggregate supply (LRAS) is vertical at the economy's full-employment output level, representing potential GDP.
短期总供给（SRAS）曲线向上倾斜，因为某些投入成本具有粘性。原材料成本、工资或税收的变化使 SRAS 曲线平移。长期总供给（LRAS）在经济充分就业产出水平上表现为一条垂直线，代表潜在 GDP。
Macroeconomic equilibrium occurs where AD meets SRAS. If equilibrium lies to the left of LRAS, a deflationary gap exists with unemployment and spare capacity; to the right, an inflationary gap occurs, putting upward pressure on prices.
宏观经济均衡出现在 AD 与 SRAS 相交处。若均衡位于 LRAS 左侧，则存在通货紧缩缺口，伴随失业和闲置产能；若位于右侧，则出现通货膨胀缺口，对价格构成上行压力。
9. Macroeconomic Policies | 宏观经济政策
Fiscal policy involves government manipulation of taxation and spending to influence AD. Expansionary fiscal policy (higher G, lower taxes) boosts AD, useful during recession; contractionary policy reduces AD to cool an overheating economy.
财政政策涉及政府操控税收与支出来影响总需求。扩张性财政政策（增加 G、降低税收）在衰退时提振 AD；紧缩性政策则减少 AD 以给过热经济降温。
Monetary policy, typically managed by a central bank, adjusts interest rates and the money supply. Lower interest rates stimulate consumption and investment, shifting AD right. Supply-side policies aim to increase LRAS by improving productivity, encouraging competition, and investing in infrastructure and education.
货币政策通常由中央银行管理，调整利率和货币供应量。降低利率刺激消费和投资，使 AD 右移。供给侧政策旨在通过提高生产率、鼓励竞争和投资基础设施与教育，增加 LRAS。
10. International Trade and Exchange Rates | 国际贸易与汇率
Countries trade to exploit comparative advantage – the ability to produce a good at a lower opportunity cost than another country. Specialisation and trade increase world output. However, protectionism (tariffs, quotas, subsidies to domestic firms) distorts trade, raising prices and reducing consumer surplus.
各国开展贸易是为了利用比较优势——以低于另一国的机会成本生产一种商品的能力。专业化与贸易增加世界产出。然而，保护主义（关税、配额、对国内企业的补贴）会扭曲贸易，抬高价格并减少消费者剩余。
Exchange rates express the value of one currency in terms of another. In a floating system, rates are determined by demand and supply for currencies, influenced by trade flows, interest rates and speculation. A depreciation of a currency makes exports cheaper and imports dearer, potentially improving a trade deficit in the long run if the Marshall-Lerner condition holds.
汇率表示一种货币以另一种货币衡量的价值。在浮动汇率制度下，汇率由货币的需求和供给决定，受贸易流动、利率和投机影响。本币贬值使出口更便宜、进口更昂贵，如果满足马歇尔-勒纳条件，从长远看可能改善贸易逆差。
Published by TutorHao | Economics Revision Series | aleveler.com
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