Year 9 CCEA Economics: Quick Reference Handbook of Formulas and Theorems | 九年级 CCEA 经济：公式定理速查手册

📚 Year 9 CCEA Economics: Quick Reference Handbook of Formulas and Theorems | 九年级 CCEA 经济：公式定理速查手册

This handbook provides a concise summary of the key formulas and economic theorems that every Year 9 CCEA Economics student should know. Mastering these fundamentals will help you analyse real-world scenarios and tackle exam questions with confidence.

本手册简明扼要地总结了每一位九年级 CCEA 经济学学生都应掌握的核心公式与定理。熟练掌握这些基础知识，将有助于你分析现实生活中的案例，并充满信心地应对考试题目。

1. Scarcity and Opportunity Cost | 稀缺性与机会成本

Scarcity is the fundamental economic problem: human wants are unlimited, but the resources (land, labour, capital, enterprise) available to satisfy them are limited. Because of scarcity, every society must answer three basic questions: What to produce? How to produce? For whom to produce?

稀缺性是经济学的基本问题：人类的欲望是无限的，但用于满足这些欲望的资源（土地、劳动、资本、企业家才能）是有限的。由于稀缺性的存在，每个社会都必须回答三个基本问题：生产什么？如何生产？为谁生产？

The concept of opportunity cost helps us measure the real cost of any choice. It is defined as the value of the next best alternative forgone. Whenever you make a decision, whether as a student, a firm, or a government, you are giving up the chance to use those resources for something else.

机会成本这一概念帮助我们衡量任何选择的真实成本。它被定义为所放弃的次优替代选择的价值。每当你做决定时，无论是作为学生、企业还是政府，你都在放弃将这些资源用于其他事情的机会。

Opportunity Cost = Value of the Next Best Alternative Forgoned

For example, if a student spends two hours revising economics instead of earning money at a part-time job, the opportunity cost is the wages lost. Rational decision-making involves weighing the expected benefits against the opportunity costs.

例如，如果一个学生花两小时复习经济学，而不是去做兼职赚钱，那么机会成本就是所损失的工资。理性的决策需要权衡预期收益与机会成本。

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2. The Law of Demand and the Demand Curve | 需求定律与需求曲线

The Law of Demand states that, ceteris paribus (all else being equal), as the price of a good or service rises, the quantity demanded falls, and as price falls, the quantity demanded rises. This inverse relationship gives the demand curve its downward slope.

需求定律指出，在其他条件不变的情况下，当商品或服务的价格上升时，需求量下降；当价格下降时，需求量上升。这种反向关系使需求曲线呈向下倾斜的特征。

It is essential to distinguish between a movement along the demand curve (caused only by a change in the own price of the good) and a shift of the demand curve (caused by changes in factors other than the good’s own price). Key demand shifters include:

区分沿着需求曲线的移动（仅由商品自身价格变化引起）和需求曲线的移动（由商品自身价格以外的因素变化引起）至关重要。主要的需求移动因素包括：

• Disposable income (normal vs inferior goods).

  可支配收入（正常品与劣等品）。

• Consumer tastes and preferences.

  消费者的口味与偏好。

• Prices of substitutes and complements.

  替代品和互补品的价格。

• Population size and demographics.

  人口规模与人口结构。

• Expectations about future prices.

  对未来价格的预期。

An increase in demand shifts the curve to the right (higher quantity demanded at every price), while a decrease shifts it to the left.

需求增加会使曲线向右移动（在每个价格水平上需求量都更高），需求减少则使曲线向左移动。

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3. The Law of Supply and the Supply Curve | 供给定律与供给曲线

The Law of Supply tells us that, ceteris paribus, as the price of a good or service increases, the quantity supplied increases, and as price decreases, quantity supplied decreases. Producers are motivated by the profit incentive – higher prices make production more attractive.

供给定律告诉我们，在其他条件不变的情况下，当商品或服务的价格上升时，供给量增加；当价格下降时，供给量减少。生产者受利润动机驱动——更高的价格使生产更具吸引力。

This positive relationship results in an upward-sloping supply curve. As with demand, we distinguish between a movement along the supply curve (caused by a price change) and a shift of the supply curve (caused by changes in other factors). Common supply shifters are:

这种正向关系导致供给曲线向上倾斜。与需求类似，我们要区分沿着供给曲线的移动（由价格变化引起）和供给曲线的移动（由其他因素变化引起）。常见的供给移动因素有：

• Production costs (wages, raw materials, energy).

  生产成本（工资、原材料、能源）。

• Technological improvements.

  技术进步。

• Taxes and subsidies.

  税收与补贴。

• Number of sellers in the market.

  市场中的卖家数量。

• Natural conditions and climate (especially for agricultural goods).

  自然条件与气候（尤其对农产品而言）。

A rightward shift indicates an increase in supply; a leftward shift indicates a decrease.

向右移动表示供给增加；向左移动表示供给减少。

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4. Market Equilibrium | 市场均衡

Market equilibrium is the point where the plans of buyers and sellers coincide: the quantity consumers wish to buy exactly equals the quantity producers wish to sell. At this price, there is no tendency for the market to change.

市场均衡是买卖双方的计划相吻合的点：消费者希望购买的数量恰好等于生产者希望出售的数量。在这个价格下，市场没有自行变动的趋势。

Equilibrium Condition: Quantity Demanded (Qd) = Quantity Supplied (Qs)

When the market price is above equilibrium, a surplus (excess supply) arises, putting downward pressure on price. When the market price is below equilibrium, a shortage (excess demand) arises, pushing price upward. The price mechanism automatically guides the market towards equilibrium.

当市场价格高于均衡价格时，会出现过剩（供过于求），使价格承压下降。当市场价格低于均衡价格时，会出现短缺（供不应求），推动价格上升。价格机制自动引导市场走向均衡。

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5. Introducing Price Elasticity of Demand | 价格需求弹性初步

Price elasticity of demand (PED) measures the responsiveness of quantity demanded to a change in the price of the good itself. It helps businesses predict how a price change will affect their sales revenue.

价格需求弹性（PED）衡量需求量对商品自身价格变化的反应程度。它帮助企业预测价格变化会如何影响销售收入。

PED = %ΔQd ÷ %ΔP

where %ΔQd = percentage change in quantity demanded, and %ΔP = percentage change in price. You can calculate each percentage change as: (New value − Original value) ÷ Original value × 100.

其中 %ΔQd 表示需求量变动的百分比，%ΔP 表示价格变动的百分比。每一部分的百分比变化可用公式计算：(新数值 − 原始数值) ÷ 原始数值 × 100。

PED Value	Meaning	Effect on Revenue
大于 1 (弹性)	需求量变化比例大于价格变化比例	降价增加总收入，涨价减少总收入
小于 1 (缺乏弹性)	需求量变化比例小于价格变化比例	涨价增加总收入，降价减少总收入
等于 1 (单位弹性)	需求量变化比例等于价格变化比例	价格变化不影响总收入

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6. Total Revenue and Total Cost | 总收益与总成本

A firm’s total revenue (TR) is the income it receives from selling its output. Total cost (TC) is the sum of all expenses incurred in producing that output. Understanding these measures is the first step in profit analysis.

企业的总收益（TR）是它通过销售产品获得的收入。总成本（TC）是生产这些产品所产生的所有开支的总和。理解这两个指标是进行利润分析的第一步。

Total Revenue (TR) = Price (P) × Quantity Sold (Q)

If a firm sells 200 units at £5 each, TR = £5 × 200 = £1,000. Total revenue changes when price or quantity sold changes.

如果一家企业以每件5英镑的价格销售200件产品，总收入 TR = £5 × 200 = £1,000。当价格或销售量变化时，总收益也会变化。

Total Cost (TC) = Total Fixed Cost (TFC) + Total Variable Cost (TVC)

Fixed costs (e.g. rent, insurance) do not vary with output in the short run, while variable costs (e.g. raw materials, wages for hourly workers) change directly with the level of production.

固定成本（如租金、保险费）在短期内不随产量变化，而可变成本（如原材料、小时工工资）直接随生产水平变化。

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7. Profit Calculation | 利润计算

Profit is the reward entrepreneurs receive for taking risks and organising production. The basic profit formula is one of the most important in business economics.

利润是企业家因承担风险和组织生产而获得的报酬。基本的利润公式是商业经济学中最重要的公式之一。

Profit (π) = Total Revenue (TR) − Total Cost (TC)

If TR exceeds TC, the firm earns a positive economic profit (supernormal profit). If TR exactly equals TC, the firm earns a normal profit (zero economic profit), which is just enough to keep resources in their current use. If TC exceeds TR, the firm makes a loss.

如果总收益大于总成本，企业获得正的经济利润（超额利润）。如果总收益恰好等于总成本，企业获得正常利润（零经济利润），这刚好足以让资源维持在当前用途。如果总成本大于总收益，企业则出现亏损。

Break-even occurs at the output level where TR = TC. At this point, the firm covers all its costs but makes no surplus profit.

盈亏平衡点出现在 TR = TC 的产量水平。此时企业覆盖了所有成本，但没有额外的利润。

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8. Money and Its Functions | 货币与货币职能

Money is anything that is generally accepted as payment for goods and services. For something to serve as money, it must fulfil four key functions:

货币是指任何被普遍接受作为商品和服务的支付手段的东西。要充当货币，必须履行以下四个关键职能：

• Medium of exchange: eliminates the need for barter by facilitating transactions.

  交换媒介：通过便利交易，消除了以物易物的需要。

• Unit of account: provides a common measure for pricing goods and comparing values.

  计价单位：为商品定价和价值比较提供了统一的尺度。

• Store of value: allows people to save and defer spending to the future.

  价值储藏：使人们能够储蓄并将消费推迟到未来。

• Standard of deferred payment: enables borrowing and lending because debts can be stated in money terms.

  延期支付标准：使借贷成为可能，因为债务可以用货币单位来表示。

These functions work only if money retains its purchasing power and is widely trusted.

这些职能只有在货币能够保持其购买力并得到广泛信任时才能实现。

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9. Inflation and Purchasing Power | 通货膨胀与购买力

Inflation is a sustained increase in the general level of prices over time. When inflation occurs, each pound buys fewer goods and services, meaning the purchasing power of money falls.

通货膨胀是指总体物价水平随着时间的推移持续上升。当通货膨胀发生时，每一英镑能购买的商品和服务减少，这意味着货币的购买力下降。

Inflation Rate = [(CPI in Current Year − CPI in Previous Year) ÷ CPI in Previous Year] × 100%

CPI (Consumer Price Index) measures the average change in prices paid by households for a basket of goods and services. A rising CPI indicates inflation; a falling CPI indicates deflation.

CPI（消费者价格指数）衡量家庭为购买一篮子商品和服务所支付价格的平均变化。CPI 上升表示通货膨胀；CPI 下降表示通货紧缩。

Purchasing power can be understood through the simple relationship: Purchasing Power = 1 ÷ Average Price Level. When the price level doubles, the purchasing power of money halves.

购买力可以通过一个简单的公式理解：购买力 = 1 ÷ 平均价格水平。当价格水平翻倍时，货币的购买力就减半。

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10. Key Economic Principles | 重要经济原理

Beyond formulas, economics is built on a number of fundamental principles that help explain behaviour.

除了公式之外，经济学还建立在一系列有助于解释行为的基本原理之上。

“There is no such thing as a free lunch.” (TINSTAAFL)

Every choice involves an opportunity cost. Even if a good appears free, resources are used up to provide it, and those resources could have been used elsewhere.

每一次选择都涉及机会成本。即使某种商品看起来是免费的，提供它也要消耗资源，而这些资源本可以用于其他地方。

• People face trade-offs: to get something we like, we usually have to give up something else.

  人们面临权衡取舍：要获得我们喜欢的东西，通常就必须放弃其他东西。

• People respond to incentives: changes in costs and benefits alter behaviour in predictable ways.

  人们会对激励作出反应：成本和收益的变化会以可预见的方式改变人们的行为。

• Rational decision-making occurs at the margin: decisions are often analysed by comparing marginal benefits (MB) and marginal costs (MC). An action is worth taking if MB > MC.

  理性决策基于边际分析：决策通常通过比较边际收益（MB）和边际成本（MC）来进行。若 MB > MC，则采取该行动是值得的。

• Markets are usually a good way to organise economic activity: the invisible hand of the price mechanism can coordinate the decisions of millions of buyers and sellers.

  市场通常是组织经济活动的一种好方式：价格机制的“看不见的手”可以协调无数买卖双方的决策。

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Published by TutorHao | Economics Revision Series | aleveler.com

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