📚 KS3 CIE Economics: Formula and Theorem Quick Reference Handbook | KS3 CIE 经济：公式定理速查手册
Welcome to your go-to quick reference for all the essential formulas, key theorems, and core concepts you will meet in KS3 CIE Economics. This handbook is designed to help you revise effectively, understand the logic behind economic reasoning, and master the quantitative skills required at this level. Keep it by your side as you work through past papers and class notes.
欢迎使用这本速查手册，它涵盖了 KS3 CIE 经济课程中所有基本公式、关键定理与核心概念。本手册旨在帮助你有针对性地复习，理解经济推理背后的逻辑，并掌握该阶段所要求的定量技能。建议你在复习真题和课堂笔记时随时查阅。
1. Scarcity and Opportunity Cost | 稀缺性与机会成本
Scarcity is the fundamental economic problem: unlimited human wants but limited resources. Because resources are finite, choices must be made. The cost of any choice is the value of the next best alternative forgone — this is called opportunity cost.
稀缺性是经济学最基本的问题：人的欲望无限，但资源有限。由于资源有限，我们必须做出选择。任何选择的成本就是所放弃的次优选择的价值——这就是机会成本。
Opportunity Cost = Value of Next Best Alternative Sacrificed
机会成本 = 所放弃的次优选择的价值
Remember that opportunity cost is not the sum of all alternatives, only the best one given up. It applies to individuals, firms, and governments.
记住，机会成本并非所有备选项的价值总和，仅仅是被放弃的最优选项。个人、企业和政府决策中都存在机会成本。
2. Factors of Production | 生产要素
Economists classify resources used to produce goods and services into four factors of production: Land, Labour, Capital, and Enterprise. Land includes all natural resources; Labour is the human effort; Capital means man-made tools and machinery; Enterprise is the risk-taking ability that organises the other three factors.
经济学家将用于生产商品和服务的资源分为四种生产要素：土地、劳动、资本和企业家才能。土地包含所有自然资源；劳动指人力付出；资本指人造工具和机器；企业家才能则是组织其他三种要素并承担风险的能力。
The rewards to each factor are: Rent for Land, Wages for Labour, Interest for Capital, and Profit for Enterprise. Understanding these rewards helps you analyse how income is distributed in an economy.
每种要素的报酬分别为：土地获得地租，劳动获得工资，资本获得利息，企业家才能获得利润。理解这些报酬有助于你分析经济中的收入分配。
3. Production Possibility Frontier (PPF) | 生产可能性边界
A PPF curve shows the maximum possible output combinations of two goods that an economy can produce when all resources are fully and efficiently employed. Points inside the curve represent inefficiency or unemployment; points on the curve are efficient; points outside are currently unattainable.
生产可能性边界曲线表示一个经济体在资源充分利用且有效配置时，所能生产的两种商品的最大产量组合。曲线内的点代表低效率或资源闲置；曲线上的点代表有效率；曲线外的点在当前条件下无法达到。
The shape of the PPF illustrates the concept of increasing opportunity cost: as you produce more of one good, you must give up increasing amounts of the other. This occurs because resources are not equally suited to all types of production.
PPF 曲线的形状体现了机会成本递增的概念：随着一种商品产量增加，必须放弃的另一种商品数量越来越多。这是因为资源并非同样适用于所有类型的生产。
Shift of PPF to the right = Economic Growth
PPF 曲线向右移动 = 经济增长
4. Demand and the Law of Demand | 需求与需求定律
Demand refers to the quantity of a good or service that consumers are willing and able to buy at various prices over a given period. The law of demand states that, ceteris paribus, as price rises, quantity demanded falls, and vice versa. This inverse relationship creates a downward-sloping demand curve.
需求指在一定时期内，消费者在不同价格水平上愿意并且能够购买的商品或服务数量。需求定律指出，在其他条件不变的情况下，价格上升，需求量下降；价格下降，需求量上升。这种反向关系形成了一条向下倾斜的需求曲线。
Law of Demand: P ↑ → Qd ↓ and P ↓ → Qd ↑ (ceteris paribus)
需求定律：P ↑ → Qd ↓ 且 P ↓ → Qd ↑（其他条件不变）
Factors that can shift the demand curve include changes in income, tastes, prices of related goods (substitutes and complements), and population size. A shift to the right means an increase in demand at every price.
能够使需求曲线移动的因素包括收入变化、偏好变化、相关商品（替代品和互补品）价格变化以及人口规模变化。曲线向右移动意味着在每个价格水平上需求都增加了。
5. Supply and the Law of Supply | 供给与供给定律
Supply is the quantity of a good or service that producers are willing and able to offer for sale at various prices. The law of supply says that, ceteris paribus, as price rises, quantity supplied rises; as price falls, quantity supplied falls. This positive relationship gives an upward-sloping supply curve.
供给指生产者在不同价格水平上愿意且能够提供出售的商品或服务数量。供给定律指出，在其他条件不变的情况下，价格上升，供给量增加；价格下降，供给量减少。这种正向关系形成了向上倾斜的供给曲线。
Law of Supply: P ↑ → Qs ↑ and P ↓ → Qs ↓ (ceteris paribus)
供给定律：P ↑ → Qs ↑ 且 P ↓ → Qs ↓（其他条件不变）
Supply curve shifters include changes in production costs, technology, taxes and subsidies, and the number of sellers. A rightward shift indicates an increase in supply.
供给曲线的移动因素包括生产成本、技术、税收与补贴以及卖者数量的变化。曲线向右移动代表供给增加。
6. Market Equilibrium and Price Mechanism | 市场均衡与价格机制
Market equilibrium occurs where the demand and supply curves intersect. At the equilibrium price, quantity demanded equals quantity supplied, so there is no shortage or surplus. The price mechanism automatically adjusts to restore equilibrium if the market is out of balance.
市场均衡出现在需求曲线与供给曲线相交之处。在均衡价格上，需求量等于供给量，因此既不存在短缺也不存在过剩。如果市场脱离平衡，价格机制会自动调节以恢复均衡。
Equilibrium condition: Qd = Qs at Pe
均衡条件：在 Pe 上 Qd = Qs
Excess demand (shortage) pushes prices up; excess supply (surplus) pushes prices down. This rationing, signalling, and incentive function of price is the heart of the market system.
超额需求（短缺）会推高价格；超额供给（过剩）会压低价格。价格的这种配给、信号和激励功能正是市场体系的核心。
7. Price Elasticity of Demand (PED) | 需求价格弹性 (PED)
Price elasticity of demand measures how responsive quantity demanded is to a change in price. It is calculated as the percentage change in quantity demanded divided by the percentage change in price.
需求价格弹性衡量需求量对价格变化的反应程度。它的计算方法是：需求量变化的百分比除以价格变化的百分比。
PED = (%Δ in Qd) / (%Δ in Price)
PED = (需求量变化百分比) / (价格变化百分比)
tors affecting PED include availability of substitutes, degree of necessity, and proportion of income spent on the good.
如果 PED > 1，需求是富有价格弹性的（消费者对价格变化敏感）。如果 PED < 1，需求缺乏价格弹性。如果 PED = 1，则为单位弹性。影响 PED 的因素包括替代品的可获得性、商品的必需程度以及该商品支出在收入中所占的比例。
8. Costs, Revenue and Profit | 成本、收益与利润
e × Quantity sold. Total cost (TC) is the sum of fixed costs (FC) and variable costs (VC).
企业需要了解其成本与收益以计算利润。总收益 (TR) 是销售商品所获得的货币：价格 × 销售数量。总成本 (TC) 是固定成本 (FC) 与可变成本 (VC) 之和。
TR = P × Q
TR = P × Q
TC = FC + VC
TC = FC + VC
Profit is total revenue minus total cost. Average cost (AC or ATC) is total cost divided by output. Marginal cost (MC) is the extra cost of producing one more unit.
利润等于总收益减去总成本。平均成本 (AC 或 ATC) 是总成本除以产量。边际成本 (MC) 是额外多生产一单位产品所增加的成本。
Profit = TR - TC
利润 = TR - TC
AC = TC ÷ Q and MC = ΔTC ÷ ΔQ
AC = TC ÷ Q 且 MC = ΔTC ÷ ΔQ
should continue producing in the short run as long as price covers average variable cost.
当 TR = TC 时，企业收支平衡。在短期内，只要价格能够覆盖平均可变成本，企业就应继续生产。
9. Market Structures: An Overview | 市场结构概览
Market structure describes the competitive environment in which firms operate. The main types are perfect competition, monopoly, oligopoly, and monopolistic competition. Each structure is defined by the number of sellers, type of product, barriers to entry, and control over price.
市场结构描述了企业所处的竞争环境。主要类型包括完全竞争、垄断、寡头垄断和垄断竞争。每种结构由卖者数量、产品类型、进入壁垒和对价格的控制程度来定义。
In perfect competition, many small firms sell identical products with no barriers to entry; they are price takers. A monopoly is a single seller with high barriers, and it is a price maker. Oligopoly involves a few large firms, often with interdependent pricing. Monopolistic competition has many firms selling differentiated products with some price-setting ability.
在完全竞争中，许多小企业销售同质产品，没有进入壁垒；它们是价格接受者。垄断是指只有一个卖者并且存在高进入壁垒，它是价格制定者。寡头垄断涉及少数几家大企业，定价常常相互依赖。垄断竞争中有许多企业销售差异化产品，并拥有一定的定价能力。
10. Government Intervention: Taxes and Subsidies | 政府干预：税收与补贴
Governments impose indirect taxes (such as VAT) on goods to raise revenue and discourage consumption. A tax shifts the supply curve to the left, raising the equilibrium price and reducing the equilibrium quantity. The burden of a tax is shared between consumers and producers.
政府通过对商品征收间接税（如增值税）来增加财政收入并抑制消费。税收使供给曲线向左移动，抬高了均衡价格、减少了均衡数量。税收负担由消费者和生产者共同分担。
Consumer Burden of Tax = (Post-tax Price - Pre-tax Price) × Post-tax Quantity
消费者税收负担 = (税后价格 - 税前价格) × 税后数量
Producer Burden = Tax per unit × Post-tax Quantity - Consumer Burden
生产者负担 = 单位税额 × 税后数量 - 消费者负担
A subsidy lowers production costs, shifting the supply curve to the right, reducing the price paid by consumers and increasing quantity. The benefit of a subsidy is also split between consumers and producers.
补贴会降低生产成本，使供给曲线向右移动，降低消费者支付的价格并增加数量。补贴的好处同样在消费者和生产者之间分配。
11. Introduction to Macroeconomics: Key Indicators | 宏观经济导论：主要指标
Macroeconomics looks at the economy as a whole. Three vital indicators are Gross Domestic Product (GDP), unemployment rate, and inflation rate. GDP measures the total value of goods and services produced in a country over a period.
宏观经济学把经济作为一个整体来研究。三个重要指标是国内生产总值 (GDP)、失业率和通货膨胀率。GDP 衡量一个国家在一定时期内生产的商品和服务的总价值。
GDP = C + I + G + (X - M)
GDP = 消费 + 投资 + 政府支出 + (出口 - 进口)
Unemployment rate is the percentage of the labour force that is without work but actively seeking employment. Inflation rate is the percentage increase in the general price level, often measured by the Consumer Price Index (CPI).
失业率是指劳动力中没有工作但正在积极寻找工作的人所占的百分比。通货膨胀率是指总体物价水平上涨的百分比，通常用消费者价格指数 (CPI) 来衡量。
Unemployment Rate = (Unemployed ÷ Labour Force) × 100%
失业率 = (失业人数 ÷ 劳动力总数) × 100%
Inflation Rate = [(CPI this year - CPI last year) ÷ CPI last year] × 100%
通货膨胀率 = [(今年 CPI - 去年 CPI) ÷ 去年 CPI] × 100%
These indicators help policymakers target economic growth, full employment, and price stability.
这些指标帮助政策制定者以实现经济增长、充分就业和物价稳定为目标。
Published by TutorHao | Economics Revision Series | aleveler.com
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