📚 Formula & Theorem Quick Reference Handbook for Year 8 Edexcel Economics | Year 8 Edexcel 经济公式定理速查手册
This quick reference handbook compiles the essential formulas, theorems, and key concepts for Year 8 Edexcel Economics. It is designed to help you revise efficiently and understand the core principles that form the foundation of economic study. Use this guide to master definitions, relationships, and simple calculations that will appear in your assessments.
这本速查手册汇编了 Year 8 Edexcel 经济学的基本公式、定理和关键概念，旨在帮助你高效复习并理解构成经济学学习基础的核心原理。利用本指南掌握定义、关系以及将在测评中出现的简单计算。
1. Scarcity and the Basic Economic Problem | 稀缺性与基本经济问题
The fundamental economic problem is scarcity: humans have unlimited wants but resources are limited. This forces individuals, firms, and governments to make choices about what to produce, how to produce, and for whom to produce.
基本经济问题是稀缺性：人类的欲望无限而资源有限。这迫使个人、企业和政府就生产什么、如何生产以及为谁生产做出选择。
Scarcity requires rationing mechanisms. In a market economy, prices perform this role; in a command economy, the government allocates resources. The existence of opportunity cost is a direct consequence of scarcity.
稀缺性需要配给机制。在市场经济中，价格充当这一角色；在计划经济中，政府分配资源。机会成本的存在是稀缺性的直接结果。
2. Opportunity Cost Formula | 机会成本公式
Opportunity cost is the value of the next best alternative forgone when a choice is made. It is not the sum of all other options, but the single most desirable option sacrificed.
机会成本是指做出选择时放弃的次优选择的价值。它不是所有其他选项的总和，而是被牺牲的那个最渴望的单一选项。
Opportunity Cost = Value of Next Best Alternative Forgone
机会成本 = 放弃的次优选价值
For example, if a government spends £10 million on a new motorway, the opportunity cost might be the schools or hospitals that could have been built with the same money. For a student, choosing to revise economics instead of watching a movie means the enjoyment and relaxation from the movie is the opportunity cost.
例如，如果政府花费1000万英镑修建一条新高速公路，机会成本可能是用同样资金本可以修建的学校或医院。对于学生而言，选择复习经济学而不是看电影，意味着看电影的享受和放松就是机会成本。
3. Law of Demand | 需求定律
The law of demand states that, ceteris paribus (all other things being equal), as the price of a good increases, the quantity demanded decreases, and as price falls, quantity demanded increases. This inverse relationship is represented by a downward-sloping demand curve.
需求定律指出，在其他条件不变的情况下，商品价格上升，需求量下降；价格下降，需求量上升。这种反比关系表现为一条向下倾斜的需求曲线。
- Determinants of demand that can shift the whole curve: income (normal vs inferior goods), tastes and fashion, prices of substitutes and complements, advertising, population changes, and expectations of future prices.
- 能够使整条需求曲线移动的需求决定因素：收入（正常品与劣等品）、品味与时尚、替代品和互补品的价格、广告、人口变化以及对未来价格的预期。
For instance, an increase in consumer income shifts demand for normal goods to the right. A rise in the price of a substitute (e.g. tea) shifts demand for coffee to the right. Always distinguish between a movement along the curve (caused by a price change) and a shift of the curve (caused by other factors).
例如，消费者收入增加会使正常品的需求曲线右移。替代品（如茶）价格上升会使咖啡的需求曲线右移。务必区分沿着曲线的移动（由价格变化引起）和整个曲线的移动（由其他因素引起）。
4. Law of Supply | 供给定律
The law of supply states that, ceteris paribus, as the price of a good rises, the quantity supplied increases, and as price falls, quantity supplied decreases. This positive relationship creates an upward-sloping supply curve.
供给定律指出，在其他条件不变的情况下，商品价格上升，供给量增加；价格下降，供给量减少。这种正比关系形成一条向上倾斜的供给曲线。
- Determinants of supply: costs of production (wages, raw materials, energy), technology improvements, taxes (increase costs, shift left) and subsidies (reduce costs, shift right), number of sellers, weather/climate (especially for agriculture), and expectations of future prices.
- 供给决定因素：生产成本（工资、原材料、能源）、技术进步、税收（增加成本，曲线左移）与补贴（降低成本，曲线右移）、卖家数量、天气/气候（尤其对农业）以及对未来价格的预期。
A good harvest due to favourable weather shifts the supply curve for wheat to the right. A new tax on sugar production shifts the supply curve for soft drinks to the left, leading to a higher equilibrium price.
由于天气有利带来的好收成会使小麦的供给曲线右移。对糖生产征收新税会使软饮料的供给曲线左移，导致更高的均衡价格。
5. Market Equilibrium and Price Mechanism | 市场均衡与价格机制
Market equilibrium occurs where the quantity demanded equals the quantity supplied. At the equilibrium price, the market clears with no excess demand or excess supply. The price mechanism is the automatic process by which prices adjust to restore equilibrium when there is a disequilibrium.
市场均衡发生在需求量等于供给量之时。在均衡价格下，市场出清，没有超额需求或超额供给。价格机制是当出现非均衡时，价格自动调整以恢复均衡的过程。
Equilibrium condition: Qd = Qs
If the market price is above equilibrium, a surplus emerges and firms begin to lower prices. If below, a shortage appears, and consumers bid up prices. Through this, the 'invisible hand' of the market moves the system back to equilibrium without central direction.
如果市场价格高于均衡水平，就会出现过剩，企业开始降价。如果低于均衡水平，就会出现短缺，消费者出价更高。通过这一过程，市场这只“看不见的手”使系统回归均衡，无需中央指令。
6. Price Elasticity of Demand (PED) | 需求价格弹性
Price elasticity of demand measures the responsiveness of quantity demanded 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。它由需求量变化百分比除以价格变化百分比计算得出。
PED = %ΔQd ÷ %ΔP
PED = 需求量变化百分比 ÷ 价格变化百分比
The absolute value is usually considered: If PED > 1, demand is elastic → a price cut raises total revenue. If PED < 1, demand is inelastic → a price rise raises total revenue. If PED = 1, demand is unitary elastic → total revenue is maximised. ability of substitutes, necessity vs luxury, proportion of income spent, and time horizon.
通常取绝对值考虑： 如果 PED > 1，需求富有弹性 → 降价增加总收益。 如果 PED < 1，需求缺乏弹性 → 提价增加总收益。 如果 PED = 1，需求单位弹性 → 总收益最大化。 影响 PED 的因素包括替代品的可获得性、必需品还是奢侈品、支出占收入的比例以及时间框架。
7. Costs of Production | 生产成本公式
Firms face different types of costs. Fixed costs do not vary with output in the short run, while variable costs change directly with the level of production. Total cost is the sum of both.
企业面临不同类型的成本。固定成本在短期内不随产量变化，而可变成本直接随生产水平变化。总成本是二者之和。
Total Cost (TC) = Fixed Cost (FC) + Variable Cost (VC)
总成本 (TC) = 固定成本 (FC) + 可变成本 (VC)
Average Cost (AC) = Total Cost ÷ Quantity (Q)
平均成本 (AC) = 总成本 ÷ 数量 (Q)
As output expands, average fixed cost falls because the fixed cost is spread over more units. This often causes average total cost to decline initially – a concept linked to economies of scale. Typical fixed costs include rent and salaries of permanent staff; variable costs include raw materials and piece-rate wages.
随着产出扩大，平均固定成本下降，因为固定成本被分摊到更多单位上。这通常导致平均总成本起初下降——这一概念与规模经济相关。典型的固定成本包括租金和固定员工的薪金；可变成本包括原材料和计件工资。
8. Revenue and Profit | 收益与利润公式
Total revenue is the income a firm receives from sales. Profit is the reward for risk-taking and is calculated by deducting total cost from total revenue.
总收益是企业从销售中获得的收入。利润是对承担风险的回报，通过总收益减去总成本来计算。
Total Revenue (TR) = Price (P) × Quantity Sold (Q)
总收益 (TR) = 价格 (P) × 销售量 (Q)
Profit = TR – TC
利润 = 总收益 – 总成本
If a company sells 200 units at £5 each, TR = £1,000. If TC is £800, profit = £ n point, TR = TC. Understanding these relationships is vital for business decision-making.
如果一家公司以每件5英镑的价格出售200件产品，TR = 1000英镑。若 TC 为800英镑，利润 = 200英镑。当 TR > TC 时，企业盈利；当 TR < TC 时，企业亏损。在盈亏平衡点，TR = TC。理解这些关系对商业决策至关重要。
9. Economic Agents and Their Objectives | 经济主体及其目标
The economy consists of three main groups of decision-makers: consumers (households), producers (firms), and the government. Each group pursues specific objectives that drive economic activity.
经济由三大决策群体构成：消费者（家庭）、生产者（企业）和政府。每个群体都追求特定目标，从而驱动经济活动。
- Consumers: aim to maximise utility (satisfaction) given their limited income. They must make choices about how to allocate their budget among different goods and services.
- 消费者：目标是在有限收入下实现效用（满意度）最大化。他们必须选择如何在不同的商品和服务之间分配预算。
- Producers: typically aim to maximise profit, but may also pursue objectives like sales maximisation, growth in market share, or social responsibility. Their decisions on price, output, and investment depend on market structure.
- 生产者：通常追求利润最大化，但也可能追求销售额最大化、市场份额增长或社会责任等目标。他们在价格、产量和投资方面的决策取决于市场结构。
- Government: aims to improve overall economic welfare. This includes correcting market failures, providing public goods, redistributing income, and managing the macroeconomy to achieve stable growth, low unemployment, and controlled inflation.
- 政府：旨在改善整体经济福利。这包括纠正市场失灵、提供公共品、再分配收入以及管理宏观经济以实现稳定增长、低失业率和受控的通货膨胀。
10. Market Failure and Externalities | 市场失灵与外部性
Market failure occurs when the free market, left alone, does not lead to an efficient allocation of resources. A significant cause is externalities – costs or benefits that affect third parties outside the market transaction.
市场失灵是指任由自由市场自行运作时，无法实现资源的有效配置。一个重要的原因是外部性——影响到市场交易之外的第三方的成本或收益。
- Negative externality: exists when the social cost exceeds the private cost. Example: factory pollution imposes health costs on nearby residents. The market overproduces the good because firms only consider their own costs. A diagram shows that the marginal social cost curve lies above the supply curve (marginal private cost), leading to a welfare loss triangle.
- 负外部性：当社会成本超过私人成本时存在。例如：工厂污染给附近居民带来健康成本。市场会过度生产该商品，因为企业只考虑自己的成本。图示显示边际社会成本曲线位于供给曲线（边际私人成本）之上，导致福利损失三角。
- Positive externality: exists when the social benefit exceeds the private benefit. Example: vaccination protects not only the individual but also the community. The market underproduces such goods. The marginal social benefit curve lies above the demand curve (marginal private benefit).
- 正外部性：当社会收益超过私人收益时存在。例如：疫苗接种不仅保护个人，也保护社区。市场会在这种商品上生产不足。边际社会收益曲线位于需求曲线（边际私人收益）之上。
Governments can use taxes to internalise negative externalities and subsidies to encourage positive externalities, moving the market towards a socially optimal output level.
政府可以使用税收来内化负外部性，使用补贴来鼓励正外部性，从而使市场向社会最优产出水平靠近。
11. International Trade and Comparative Advantage | 国际贸易与比较优势
International trade allows countries to specialise in producing goods where they have a comparative advantage – the ability to produce a good at a lower opportunity cost than another country. This principle, developed by David Ricardo, shows that even if one country is more efficient at producing everything (absolute advantage), both countries can still benefit from trade.
国际贸易使各国能够专业化生产自己具有比较优势的商品——即能够以低于另一国的机会成本生产某种商品的能力。这一由大卫·李嘉图提出的原理表明，即使一国在生产所有商品上都更有效率（绝对优势），两国仍能从贸易中获益。
Specialisation increases total world output, and exchange allows both nations to consume beyond their own production possibility frontiers. Barriers to trade, such as tariffs and quotas, can reduce these gains.
专业化提高了世界总产出，交换使两国都能超越自身的生产可能性边界进行消费。关税和配额等贸易壁垒会减少这些收益。
12. Key Diagram Summary | 关键图表总结
Being able to interpret and draw economic diagrams is an essential skill. The table below summarises the main diagrams you should recognise and what they illustrate.
能够解读和绘制经济图表是一项基本技能。下表总结了你应该识别的主要图表及其说明的内容。
| Diagram | What it Shows | 图表 | 展示内容 |
|---|---|---|---|
| Demand Curve (D) | Downward slope; inverse relationship between price and quantity demanded | 需求曲线 (D) | 向下倾斜；价格与需求量反比关系 |
| Supply Curve (S)
Published by TutorHao | Year 8 Economics Revision Series | aleveler.com
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