Year 7 OCR Economics: Formula & Theorem Quick Reference | Year 7 OCR 经济：公式定理速查手册

📚 Year 7 OCR Economics: Formula & Theorem Quick Reference | Year 7 OCR 经济：公式定理速查手册

In economics, mastering the essential formulas and theorems gives you a solid scaffold to analyse everyday decisions, markets, and government policies. This quick reference handbook pulls together the core equations and principles from the Year 7 OCR Economics syllabus so you can revise efficiently and apply them confidently in class and in exams.

在经济学中，掌握基本的公式和定理能为你分析日常决策、市场与政府政策提供一个坚实的框架。这本速查手册汇集了 Year 7 OCR 经济学课程的核心方程与原理，帮助你高效复习，并在课堂和考试中自信地运用它们。

1. The Basic Economic Problem (Scarcity) | 基本经济问题（稀缺性）

The fundamental economic problem is that human wants are unlimited while the resources available to satisfy them are limited. This forces every society to answer three key questions: what to produce, how to produce, and for whom to produce.

基本经济问题在于人类的欲望是无限的，但满足这些欲望的资源是有限的。这就迫使每个社会回答三个关键问题：生产什么、如何生产以及为谁生产。

Scarcity is not the same as poverty: it applies equally to wealthy and poor nations because time, natural endowments, and productive capacity are always finite. Economics is therefore the study of how people make choices under conditions of scarcity.

稀缺性不等于贫困：它同样适用于富裕国家和贫穷国家，因为时间、自然资源和生产能力总是有限的。因此，经济学研究的是人们在稀缺条件下如何做出选择。

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2. Opportunity Cost Theorem | 机会成本定理

Opportunity cost is the value of the next best alternative forgone when a decision is made. It captures the true cost of any choice and lies at the heart of all economic decision‑making.

机会成本是做出一个决策时所放弃的次优选择的价值。它体现了任何选择的真正成本，是所有经济决策的核心。

Opportunity Cost = Value of Next Best Alternative Given Up

机会成本 = 放弃的次优选择的价值

For instance, if a farmer uses a field to grow wheat instead of barley, the opportunity cost is the profit that could have been made from barley. This concept reminds us that every ‘yes’ also means saying ‘no’ to something else.

例如，如果一个农民用一块地种植小麦而不是大麦，机会成本就是原本种植大麦可以赚取的利润。这个概念提醒我们，每一次“是”也意味着对别的事物说“不”。

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3. Factors of Production | 生产要素

Economists classify productive resources into four categories. These inputs are combined to produce goods and services, and the income earned from each factor has a distinct name.

经济学家将生产性资源分为四类。这些投入被组合起来生产商品和服务，每种要素所赚取的收入都有一个特定的名称。

Factor 要素	Description 描述	Reward 回报
Land 土地	All natural resources used in production (e.g. minerals, forests, water). 所有用于生产的自然资源（如矿产、森林、水）。	Rent 租金
Labour 劳动	The human effort, both physical and mental, used to produce goods and services. 用于生产商品和服务的人力，包括体力和脑力。	Wages/Salaries 工资/薪水
Capital 资本	Man‑made resources that aid future production (e.g. machinery, tools, buildings). 用于辅助未来生产的人造资源（如机器、工具、建筑）。	Interest 利息
Enterprise 企业精神	The ability to organise the other three factors, take risks, and innovate. 组织其他三种要素、承担风险和创新的能力。	Profit 利润

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4. Demand and Supply Functions | 需求与供给函数

Demand is the quantity of a good or service that consumers are willing and able to buy at each price, ceteris paribus. The relationship is usually inverse: as price rises, quantity demanded falls.

需求是指在其他条件不变的情况下，消费者在各个价格水平上愿意并且能够购买的商品或服务的数量。这种关系通常是反向的：价格上升，需求量下降。

Qd = a − bP (a = intercept, b = slope 截距, 斜率)

Supply is the quantity that producers are willing and able to sell at each price. Generally, a direct relationship holds: as price increases, quantity supplied increases.

供给是生产者在各个价格水平上愿意并且能够销售的数量。通常存在正向关系：价格上升，供给量增加。

Qs = c + dP (c = intercept, d = slope 截距, 斜率)

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5. Equilibrium Condition | 均衡条件

A market is in equilibrium when the quantity demanded equals the quantity supplied at a given price. There is no tendency for the price to change unless an external shock shifts demand or supply.

当在某一价格下需求量等于供给量时，市场达到均衡。除非外部冲击使需求或供给发生移动，否则价格没有变动的趋势。

Equilibrium: Qd = Qs
均衡：Qd = Qs

If the actual price is above equilibrium, a surplus emerges, putting downward pressure on price. If it is below equilibrium, a shortage arises, driving prices up. The automatic movement toward equilibrium is a cornerstone of market economics.

如果实际价格高于均衡价格，出现过剩，价格面临下行压力。如果低于均衡价格，出现短缺，推动价格上升。市场自动趋向均衡是市场经济的一个基石。

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6. Price Elasticity of Demand (PED) | 需求价格弹性

PED measures the responsiveness of quantity demanded to a change in the good’s own price. It indicates whether consumers are sensitive to price changes.

需求价格弹性衡量需求量对该商品自身价格变化的反应程度。它表明消费者对价格变化是否敏感。

PED = (%Δ in Quantity Demanded) ÷ (%Δ in Price)
需求价格弹性 = (需求量变动的%) ÷ (价格变动的%)

A PED greater than 1 (ignoring the negative sign) denotes elastic demand; less than 1 denotes inelastic demand. Knowledge of PED helps businesses set prices and predict revenue changes.

PED 的绝对值大于 1 表示需求富有弹性；小于 1 表示缺乏弹性。了解 PED 有助于企业制定价格并预测收入变化。

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7. Price Elasticity of Supply (PES) | 供给价格弹性

PES captures how readily quantity supplied responds to a price change. It depends on factors such as the flexibility of producers, the time period, and the extent of spare capacity.

供给价格弹性反映供给量对价格变化的反应速度。它取决于生产者的灵活性、时间周期以及闲置产能的程度等因素。

PES = (%Δ in Quantity Supplied) ÷ (%Δ in Price)
供给价格弹性 = (供给量变动的%) ÷ (价格变动的%)

When PES > 1, supply is elastic; when PES < 1, supply is inelastic. In very short time frames, supply tends to be highly inelastic because firms cannot easily alter output.

当 PES > 1 时，供给富有弹性；当 PES < 1 时，供给缺乏弹性。在极短的时间内，供给往往高度缺乏弹性，因为企业难以轻易改变产量。

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8. Income Elasticity of Demand (YED) | 收入需求弹性

YED measures how much the demand for a good changes when consumers’ real income changes. It categorises goods as normal or inferior.

收入需求弹性衡量消费者的实际收入变化时，对某种商品需求的变化程度。它将商品分为正常品和低档品。

YED = (%Δ in Quantity Demanded) ÷ (%Δ in Real Income)
收入需求弹性 = (需求量变动的%) ÷ (实际收入变动的%)

A positive YED signals a normal good (with a value greater than 1 indicating a luxury, and between 0 and 1 a necessity). A negative YED identifies an inferior good – as income rises, demand falls.

YED 为正表示正常品（值大于 1 表示奢侈品，介于 0 和 1 之间表示必需品）。YED 为负则表明是低档品——收入增加，需求反而下降。

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9. Total, Average and Marginal Concepts | 总量、平均量与边际量

In production analysis, economists distinguish between total, average, and marginal measures. These relationships help firms decide optimal output levels.

在生产分析中，经济学家区分总量、平均量和边际量。这些关系帮助企业确定最优产出水平。

Total Product (TP) = Total output from all units of input.
总产量 = 所有投入单位的总产出。

Average Product (AP) = TP ÷ Quantity of Input.
平均产量 = 总产量 ÷ 投入量。

Marginal Product (MP) = ΔTP ÷ ΔInput.
边际产量 = 总产量变动量 ÷ 投入变动量。

When marginal product exceeds average product, the average rises; when it falls below, the average falls. This law of diminishing marginal returns explains why short‑run output cannot be expanded indefinitely.

当边际产量大于平均产量时，平均产量上升；当边际产量小于平均产量时，平均产量下降。边际报酬递减法则解释了为什么短期产出不能无限扩大。

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10. Profit Maximisation Rule | 利润最大化规则

A firm aiming to maximise profit produces the quantity where marginal revenue (MR) equals marginal cost (MC). Producing beyond this point would add more to cost than to revenue.

追求利润最大化的企业会按照边际收益（MR）等于边际成本（MC）的产量进行生产。超过这一点，多生产一单位带来的成本将超过收益。

Profit‑maximising output: MR = MC
利润最大化产出：MR = MC

If MR > MC, the firm should expand output because the additional unit adds more to revenue than to cost. If MR < MC, the firm should contract output. This marginal thinking is central to business economics.

如果 MR > MC，企业应扩大产量，因为额外一单位带来的收入增加大于成本增加。如果 MR < MC，企业应减少产量。这种边际思维方式是企业经济学的核心。

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11. Money and its Functions | 货币及其职能

Money is any asset that is generally accepted as a medium of exchange. For an asset to function well as money, it must perform four key roles.

货币是任何被普遍接受作为交换媒介的资产。一种资产要很好地充当货币，必须履行四项关键职能。

• Medium of exchange 交换媒介 – avoids barter and the need for a double coincidence of wants. 避免物物交换和需要双重需求巧合。
• Unit of account 计价单位 – provides a common measure for comparing the value of goods. 为比较商品价值提供共同的度量标准。
• Store of value 价值储藏 – allows purchasing power to be transferred into the future. 使购买力能够转移到未来。
• Standard of deferred payment 延期支付标准 – facilitates lending and repayment. 便利借贷与偿还。

Modern fiat money has value because people have confidence in the issuing government. Without properly functioning money, specialisation and trade become extremely difficult.

现代法定货币之所以具有价值，是因为人们对发行货币的政府抱有信心。若没有运转良好的货币，专业化和贸易将变得极其困难。

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12. Specialisation and the Division of Labour | 专业化与劳动分工

Specialisation occurs when individuals, firms, or nations concentrate on a narrow range of tasks or products. Division of labour breaks the production process into small, repetitive steps, each performed by a different worker.

专业化发生在个人、企业或国家集中精力从事少数几项任务或产品时。劳动分工把生产流程分解为小的、重复的步骤，每个步骤由不同的工人完成。

Key benefits include higher output per worker (productivity gains), time saved from not switching tasks, and the scope for using machinery. However, monotonous work can reduce motivation and increase worker alienation.

主要好处包括每名工人的产出提高（生产率提升）、免于切换任务而节省时间，以及使用机器的机会。但单调的工作可能降低积极性，并增加工人的疏离感。

Proposition: Total output > self‑sufficient output.
命题：总产出 > 自给自足时的产出。

When people specialise, they rely on trade to obtain what they do not produce themselves. This interdependence is the foundation of modern economies, creating both opportunities and vulnerabilities.

当人们实行专业化时，他们依赖贸易来获取自己不生产的东西。这种相互依存是现代经济的基础，既创造机遇也带来了脆弱性。

Published by TutorHao | Economics Revision Series | aleveler.com

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