📚 Formula Cheat Sheet for IGCSE CCEA Economics | IGCSE CCEA 经济：公式汇总手册
This article brings together all the key formulas you need to master for the IGCSE CCEA Economics examination. Whether you are tackling microeconomic calculations or analysing macroeconomic performance, a solid grasp of these equations will sharpen your answers and boost your confidence. Each section explains the formula, how to apply it, and pairs English and Chinese explanations side by side.
本文为你系统整理了 IGCSE CCEA 经济学考试必须掌握的所有核心公式。无论是微观经济计算还是宏观经济表现分析，熟练掌握这些公式都能让你的答题更加精准、从容。每个小节都先给出英文解释，再提供对应的中文说明，帮助你彻底消化每一个知识点。
1. Price Elasticity of Demand (PED) | 需求价格弹性
Price elasticity of demand measures how much the quantity demanded of a product responds to a change in its own price. The basic formula is the percentage change in quantity demanded divided by the percentage change in price.
需求价格弹性衡量一种商品的需求量对其自身价格变动的反应程度。基本公式是用需求量变动的百分比除以价格变动的百分比。
PED = %ΔQd / %ΔP
To compare the sizes of changes fairly, we always work with percentage changes. The percentage change in any variable is found by combining the new value and the old value.
为了公平地比较变动幅度，我们总是使用百分比变化。任何变量的百分比变化都可以通过新值与旧值计算得到。
%Δ = (New value - Old value) / Old value × 100
Interpretation of the absolute value of PED: if it is greater than 1, demand is price elastic; less than 1, demand is price inelastic; exactly 1, demand is unit elastic.
依据 PED 绝对值进行判断：大于 1 则为富有弹性，小于 1 则为缺乏弹性，等于 1 则为单位弹性。
2. Income Elasticity of Demand (YED) | 需求收入弹性
Income elasticity of demand indicates how responsive demand for a good is to a change in consumers' income. It helps classify goods into normal goods (positive YED) and inferior goods (negative YED).
需求收入弹性反映商品需求对消费者收入变化的反应程度，可用于区分正常商品（YED 为正）和低档商品（YED 为负）。
YED = %ΔQd / %ΔY
Where %ΔQd is the percentage change in quantity demanded, and %ΔY is the percentage change in income. For luxury goods, YED is usually greater than 1; for necessities, it lies between 0 and 1.
其中 %ΔQd 是需求量的百分比变化，%ΔY 是收入的百分比变化。奢侈品的 YED 通常大于 1，必需品的 YED 介于 0 和 1 之间。
3. Cross Elasticity of Demand (XED) | 需求交叉弹性
Cross elasticity of demand measures the responsiveness of demand for good A when the price of good B changes. It identifies substitutes (positive XED) and complements (negative XED).
需求交叉弹性衡量商品 B 价格变动时，商品 A 的需求量如何反应。正数表示替代品，负数表示互补品。
XED = %ΔQd of good A / %ΔP of good B
The larger the positive XED, the closer the substitute relationship. Unrelated goods have an XED close to zero.
正的 XED 越大，替代关系越紧密。无关商品的 XED 接近于零。
4. Price Elasticity of Supply (PES) | 供给价格弹性
Price elasticity of supply indicates how much the quantity supplied changes in response to a price change. Producers' ability to adjust output over different time horizons greatly affects PES.
供给价格弹性表示价格变动时供给量的反应程度。生产者在不同时间内调整产量的能力对 PES 影响很大。
PES = %ΔQs / %ΔP
Where %ΔQs is the percentage change in quantity supplied. Supply is price elastic when PES > 1 and price inelastic when PES < 1.
%ΔQs 是供给量的百分比变化。PES 大于 1 时供给富有弹性，小于 1 时供给缺乏弹性。
5. Costs of Production | 生产成本
Understanding cost structures is essential for analysing a firm's supply decisions. Key cost formulas you must know for IGCSE CCEA are listed below.
理解成本结构是分析企业供给决策的基础。以下是 IGCSE CCEA 考试必须掌握的关键成本公式。
Total cost is the sum of all fixed costs and variable costs. Fixed costs do not vary with output, while variable costs change directly with the level of production.
总成本是所有固定成本与可变成本之和。固定成本不随产量变化，可变成本则随生产水平直接变动。
TC = TFC + TVC
Average cost (or unit cost) tells us the cost of producing one typical unit of output.
平均成本（单位成本）表示生产一单位产品所花费的成本。
AC = TC / Q
Average fixed cost and average variable cost can be isolated to see how cost components behave as output expands.
通过计算平均固定成本和平均可变成本，可以观察成本组成如何随产量扩大而变化。
AFC = TFC / Q, AVC = TVC / Q
Marginal cost is the extra cost incurred from producing one more unit. It is crucial for determining the profit‑maximising level of output.
边际成本是每多生产一单位产品所增加的成本，它是确定利润最大化产量的关键。
MC = ΔTC / ΔQ
6. Revenue Concepts | 收入概念
Revenue flows are the lifeblood of a business. The following equations connect price, quantity sold, and marginal changes.
收入流是企业的命脉。以下公式将价格、销售量和边际变动联系在一起。
Total revenue is simply the price per unit multiplied by the quantity sold.
总收入即单位价格乘以销售量。
TR = P × Q
Average revenue is total revenue divided by quantity, which is always equal to the price if all units are sold at the same price.
平均收入等于总收入除以销售量，如果所有商品都以相同价格出售，平均收入就等于价格。
AR = TR / Q = P
Marginal revenue is the change in total revenue resulting from selling one additional unit. In perfectly competitive markets, MR equals price; in imperfect markets, MR falls faster than AR.
边际收入是多销售一单位产品所带来的总收入变化。在完全竞争市场中，MR 等于价格；在不完全市场中，MR 比 AR 下降得更快。
MR = ΔTR / ΔQ
7. Profit and Break-Even | 利润与盈亏平衡
Profit is the ultimate reward for taking risk. Break‑even analysis allows a firm to know the minimum output needed to cover all costs.
利润是承担风险的最终回报。盈亏平衡分析能让企业了解覆盖所有成本所需的最低产量。
Profit can be expressed as the difference between total revenue and total cost.
利润可以表示为总收入与总成本之差。
Profit = TR - TC
The break‑even point is where a firm makes neither a profit nor a loss. At this output, total revenue equals total cost. The formula using contribution per unit is particularly useful.
盈亏平衡点是指企业既不盈利也不亏损的产量水平，此时总收入等于总成本。使用单位边际贡献的公式特别实用。
Break-even output = TFC / (Price - AVC)
The term (Price - AVC) is called the contribution per unit. Once the break‑even output is passed, each additional unit sold adds this contribution to profit.
（价格 - 平均可变成本）被称为单位边际贡献。一旦超过盈亏平衡产量，每多售出一单位产品就会为利润增加这份贡献。
8. Labour Productivity | 劳动生产率
Labour productivity is a measure of efficiency. It shows how much output is generated per worker (or per hour worked) and is a key driver of competitiveness.
劳动生产率是效率的衡量指标，用来显示每位工人（或每工作小时）创造多少产出，是竞争力的核心驱动因素。
Labour productivity = Total output / Number of workers
A higher figure means that each worker is producing more, often due to better skills, technology or capital investment.
数值越高表示每个工人产出越多，这往往得益于更好的技能、技术或资本投入。
9. Macroeconomic Formulas: GDP, Growth, Unemployment and Inflation | 宏观公式：GDP、增长率、失业与通胀
Macroeconomic performance is evaluated using a handful of closely watched indicators. The formulas below are frequently examined.
宏观经济表现通过少数密切关注的指标进行评估，以下公式是考试中的高频考点。
GDP using the expenditure approach sums up the main spending components in an economy: consumption, investment, government spending and net exports.
用支出法计算的 GDP，是将经济体中的主要支出项目相加：消费、投资、政府购买和净出口。
GDP = C + I + G + (X - M)
Where C is consumption, I investment, G government spending, X exports and M imports. Net exports are (X - M).
其中 C 代表消费，I 代表投资，G 代表政府支出，X 代表出口，M 代表进口，净出口为（X - M）。
Economic growth is measured by the percentage change in real GDP from one period to the next.
经济增长通过实际 GDP 从一个时期到下一时期的百分比变化来衡量。
Growth rate = (GDPᵗ - GDPᵗ⁻¹) / GDPᵗ⁻¹ × 100
The superscripts t and t-1 refer to the current and previous time periods. Always use real GDP to strip out the effects of inflation.
上标 t 和 t-1 分别表示当前期和上一期。务必使用实际 GDP 以剔除通货膨胀影响。
The unemployment rate expresses the number of people actively seeking work as a proportion of the total labour force.
失业率将积极寻找工作的人数表达为劳动力总数的比例。
Unemployment rate = (Number unemployed / Labour force) × 100
The labour force includes both the employed and the unemployed. Those not looking for work are not part of the labour force.
劳动力包括就业者和失业者，不寻找工作的人不属于劳动力。
Inflation is typically calculated using the Consumer Price Index (CPI). The rate of inflation is the annual percentage rise in the CPI.
通货膨胀通常使用消费价格指数（CPI）来计算。通胀率就是 CPI 的年度百分比上升幅度。
Inflation rate = (CPIᵗ - CPIᵗ⁻¹) / CPIᵗ⁻¹ × 100
If the CPI basket cost £120 this year and £100 last year, the inflation rate is ((120-100)/100)×100 = 20%.
如果今年的 CPI 篮子成本为 120 英镑，去年为 100 英镑，则通胀率为（（120-100）/100）×100 = 20%。
10. Exchange Rates and Terms of Trade | 汇率与贸易条件
Exchange rates and terms of trade both influence a country's international competitiveness. Simple calculations help interpret their movements.
汇率和贸易条件都影响一国的国际竞争力。简单的计算有助于解读它们的变动。
ange rate calculations often ask you to convert one currency into another. For example, if £1 = $1.25, then $1 = £1 / 1.25 = £0.80.
汇率计算经常要求你将一种货币兑换成另一种。例如，如果 1 英镑 = 1.25 美元，那么 1 美元 = 1 / 1.25 = 0.80 英镑。
When an exchange rate is revalued or devalued by a certain percentage, apply the percentage change to the original rate.
当汇率升值或贬值一定百分比时，需在原汇率的基础上使用百分比变化。
New rate = Old rate × (1 + percentage change)
Use a minus sign for a depreciation. This works for both direct and indirect quotations as long as you stay consistent.
贬值时用减号。无论是直接标价法还是间接标价法，只要保持前后一致即可。
The terms of trade index compares a country's export prices to its import prices. An improvement means a country can buy more imports for a given volume of exports.
贸易条件指数将一个国家的出口价格与进口价格进行对比。贸易条件改善意味着给定出口量可以换回更多进口品。
Terms of trade = (Index of export prices / Index of import prices) × 100
An increase in the index above 100 signals an improvement; a decrease signals a deterioration.
指数上升超过 100 表示贸易条件改善，下降则表示恶化。
11. The Multiplier Effect | 乘数效应
The multiplier shows how an initial injection of spending into the economy leads to a larger final increase in national income. Understanding the relationship with MPC and MPS is vital.
乘数效应表明，经济中的一笔初始支出注入如何导致国民收入的最终增长被放大。理解它与边际消费倾向（MPC）和边际储蓄倾向（MPS）的关系至关重要。
Multiplier (k) = 1 / (1 - MPC) or k = 1 / MPS
nt. If people spend 80p of every extra pound (MPC = 0.8), the multiplier is 1/(1-0.8) = 5.
因为 MPC + MPS = 1，这两个公式是等价的。如果人们每增加 1 英镑收入会花掉 80 便士（MPC = 0.8），乘数就是 1/(1-0.8) = 5。
The total change in national income is found by multiplying the size of the injection by the multiplier.
国民收入的总变动等于注入的规模乘以乘数。
ΔNational income = Injection × k
12. Other Useful Formulas | 其他常用公式
These supplementary formulas often appear in data‑response questions and can help you earn easy marks by relating economic concepts to real‑world figures.
以下补充公式常在数据分析题中出现，能将经济概念与现实数据联系起来，帮助你轻松拿分。
GDP per capita gives an average income measure and is a common indicator of living standards.
人均 GDP 提供了一种平均收入度量，是常用的生活水平指标。
GDP per capita = Total real GDP / Population
Real interest rate adjusts the nominal interest rate for inflation, showing the true cost of borrowing or the true reward for saving.
实际利率是在名义利率中剔除通胀影响后的利率，反映借贷的真实成本或储蓄的真实回报。
Real interest rate = Nominal interest rate - Inflation rate
The participation rate (or activity rate) shows the proportion of the working‑age population that is part of the labour force.
劳动力参与率显示工作年龄人口中属于劳动力的比例。
Participation rate = (Labour force / Working‑age population) × 100
Keep these formulas organised and practise applying them to past‑paper scenarios. The more fluent you become, the more time you will have to craft high‑quality evaluation paragraphs.
整理好这些公式，并多结合历年真题进行练习。越是熟练，你就能留出越多时间来书写高质量的评价段落。
Published by TutorHao | Economics Revision Series | aleveler.com
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