GCSE CIE Economics: Formula Summary Handbook | CIE GCSE 经济学：公式汇总手册

📚 GCSE CIE Economics: Formula Summary Handbook | CIE GCSE 经济学：公式汇总手册

This handbook collects every essential formula you will need for the CIE IGCSE Economics exams. Each formula is presented clearly, followed by a plain-language explanation and a simple worked example where appropriate. Use it as a quick-reference revision tool to ensure you never lose marks on calculation questions.

本手册汇总了 CIE IGCSE 经济学考试所需的所有核心公式。每个公式都以清晰的方式呈现，并附有通俗易懂的解释和相应的简单计算示例。请将它用作快速查阅的复习工具，确保你在计算题上绝不丢分。

1. Price Elasticity of Demand (PED) | 需求的价格弹性

PED measures how much the quantity demanded of a product responds to a change in its price.

需求的价格弹性衡量的是某种产品的需求量对其自身价格变动的反应程度。

PED = %ΔQ_d / %ΔP

%ΔQ_d is the percentage change in quantity demanded; %ΔP is the percentage change in price. Always use the midpoint formula if the data allows, but the standard ‘change over original × 100’ is expected in CIE IGCSE.

%ΔQ_d 表示需求量的变动百分比；%ΔP 表示价格的变动百分比。如果题目数据允许，通常应使用中点公式，但在 CIE IGCSE 考试中，标准的 ‘变化量除以原值再乘以 100’ 方法即可。

If PED > 1, demand is price elastic; if PED < 1, demand is price inelastic; if PED = 1, demand is unit elastic. A negative sign is ignored when describing elasticity.

若 PED > 1，需求是富有价格弹性的；若 PED < 1，需求是缺乏价格弹性的；若 PED = 1，需求是单位弹性的。描述弹性时通常会忽略负号。

Example: The price of a cinema ticket rises from $10 to $12, and the number of tickets sold falls from 500 to 400. %ΔP = (2/10) × 100 = 20%. %ΔQ_d = (-100/500) × 100 = -20%. PED = -20% / 20% = -1 → unit elastic (ignoring sign).

示例：一张电影票的价格从 10 美元上涨到 12 美元，售出票数从 500 张下降至 400 张。%ΔP = (2/10) × 100 = 20%。%ΔQ_d = (-100/500) × 100 = -20%。PED = -20% / 20% = -1 → 单位弹性（忽略负号）。

2. Price Elasticity of Supply (PES) | 供给的价格弹性

PES measures the responsiveness of the quantity supplied of a product to a change in its price.

供给的价格弹性衡量的是产品供给量对其价格变动的反应程度。

PES = %ΔQ_s / %ΔP

%ΔQ_s is the percentage change in quantity supplied; %ΔP is the percentage change in price. PES is almost always positive because a higher price encourages firms to supply more.

%ΔQ_s 表示供给量的变动百分比；%ΔP 表示价格的变动百分比。PES 几乎总是正值，因为更高的价格会激励企业提供更多的产品。

If PES > 1, supply is price elastic; if PES < 1, supply is price inelastic; if PES = 1, supply is unit elastic. The main determinants are time period, availability of stocks, and spare capacity.

若 PES > 1，供给是富有弹性的；若 PES < 1，供给是缺乏弹性的；若 PES = 1，供给是单位弹性的。主要影响因素包括时间周期、库存可得性以及闲置产能。

Example: The price of rubber increases by 15%. The quantity supplied increases by 30%. PES = 30% / 15% = 2, so supply is price elastic.

示例：橡胶价格上升了 15%，供给量增加了 30%。PES = 30% / 15% = 2，因此供给是富有弹性的。

3. Income Elasticity of Demand (YED) | 需求的收入弹性

YED measures the responsiveness of demand for a product to a change in consumers’ income.

需求的收入弹性衡量的是产品需求对消费者收入变动的反应程度。

YED = %ΔQ_d / %ΔY

%ΔQ_d is the percentage change in quantity demanded; %ΔY is the percentage change in real income. The sign of YED tells us whether the good is normal or inferior.

%ΔQ_d 表示需求量的变动百分比；%ΔY 表示实际收入的变动百分比。YED 的正负号可以告诉我们该商品是正常品还是低档品。

YED > 0 → normal good. If YED > 1, it is a luxury good (income elastic). If 0 < YED < 1, it is a necessity (income inelastic). YED < 0 → inferior good.

YED > 0 → 正常品。若 YED > 1，则为奢侈品（富有收入弹性）。若 0 < YED < 1，则为必需品（缺乏收入弹性）。YED < 0 → 低档品。

Example: Income rises by 5%, and demand for bakery bread rises by 2%. YED = 2% / 5% = 0.4, so bread is a normal necessity. Demand for inter-country bus travel falls by 3%; YED = -3% / 5% = -0.6, so bus travel is an inferior good.

示例：收入上升 5%，面包的需求量上升 2%。YED = 2% / 5% = 0.4，因此面包属于正常必需品。城际巴士旅行的需求下降了 3%；YED = -3% / 5% = -0.6，因此巴士旅行是低档品。

4. Cross Elasticity of Demand (XED) | 需求的交叉弹性

XED measures how the demand for one good responds to a change in the price of another good.

需求的交叉弹性衡量的是某种商品的需求对另一种商品价格变动的反应程度。

XED = %ΔQ_d of good A / %ΔP of good B

The sign of XED indicates the relationship between the two goods. A positive XED means the goods are substitutes. A negative XED means they are complements. An XED close to 0 means the goods are unrelated.

XED 的正负号表明了两种商品之间的关系。正的 XED 代表两种商品是替代品。负的 XED 代表它们是互补品。XED 接近 0 则代表它们是无关联的商品。

Example: The price of coffee rises by 10%, and the demand for tea increases by 8%. XED = 8% / 10% = +0.8, so tea and coffee are substitutes.

示例：咖啡的价格上升了 10%，茶的需求量增加了 8%。XED = 8% / 10% = +0.8，因此茶和咖啡是替代品。

5. Costs, Revenues and Profit | 成本、收益与利润

These formulas form the backbone of a firm’s financial decisions. They are frequently tested in the exam.

这些公式构成了企业财务决策的基础，在考试中经常出现。

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

总成本 (TC) = 总固定成本 (TFC) + 总可变成本 (TVC)
Average Cost (AC) = TC / Output (Q)

平均成本 (AC) = 总成本 / 产量 (Q)
Marginal Cost (MC) = ΔTC / ΔQ

边际成本 (MC) = 总成本的变化量 / 产量的变化量

Total fixed costs do not change with output (e.g., rent), while total variable costs change with output (e.g., raw materials). Marginal cost is the cost of producing one extra unit of output.

总固定成本不随产量的变化而变化（如租金），而总可变成本会随产量变化（如原材料）。边际成本是每多生产一单位产品所增加的成本。

On the revenue side:

在收益方面：

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

总收益 (TR) = 价格 (P) × 销售量 (Q)
Average Revenue (AR) = TR / Q = Price

平均收益 (AR) = 总收益 / 销售量 = 价格
Marginal Revenue (MR) = ΔTR / ΔQ

边际收益 (MR) = 总收益的变化量 / 销售量的变化量

Finally, profit is the difference between total revenue and total cost.

最后，利润是总收益与总成本之间的差值。

Profit = TR – TC

利润 = 总收益 – 总成本

Example: A firm sells 200 units at $15 each. TR = 200 × $15 = $3,000. If total fixed costs are $800 and total variable costs are $1,200, TC = $2,000. Profit = $3,000 – $2,000 = $1,000. AC = $2,000 / 200 = $10 per unit.

示例：某企业以每件 15 美元的价格售出 200 件产品。TR = 200 × 15 = 3000 美元。若总固定成本为 800 美元，总可变成本为 1200 美元，则 TC = 2000 美元。利润 = 3000 – 2000 = 1000 美元。AC = 2000 / 200 = 每件 10 美元。

6. Productivity and Efficiency | 生产率与效率

Labour productivity measures output per worker over a specific time period. It can be used to compare performance over time or between firms.

劳动生产率衡量的是每个工人在特定时期内所生产的产出。它可以用来对比不同时期或不同企业之间的绩效。

Labour Productivity = Total Output / Number of Workers

劳动生产率 = 总产出 / 工人数量

Higher labour productivity reduces average costs and can make a firm more competitive. It can be improved through training, better technology, and motivational methods.

更高的劳动生产率能够降低平均成本，使企业更具竞争力。可以通过培训、改进技术和激励手段来提高。

Capital productivity can also be calculated: Output / Units of capital used. This appears less frequently at IGCSE but follows the same logic.

也可以计算资本生产率：产出 / 使用的资本单位数。这在 IGCSE 中出现较少，但逻辑相同。

Example: A factory produces 5,000 toys in a week with 50 workers. Labour productivity = 5,000 / 50 = 100 toys per worker per week.

示例：某工厂一周内生产了 5000 个玩具，雇佣了 50 名工人。劳动生产率 = 5000 / 50 = 每个工人每周 100 个玩具。

7. Unemployment Rate | 失业率

The unemployment rate shows the percentage of the labour force that is actively seeking work but cannot find a job.

失业率反映的是在劳动力中积极寻找工作但无法找到工作的人所占的百分比。

Unemployment Rate = (Number of Unemployed / Labour Force) × 100

失业率 = (失业人数 / 劳动力总数) × 100

The labour force consists of all people who are employed plus those who are unemployed and actively seeking work. Retired people, full-time students, and those who have stopped looking are not part of the labour force.

劳动力包括所有就业者以及失业但正在积极寻找工作的人。退休人员、全日制学生以及放弃寻找工作的人不属于劳动力。

Example: If a country has 40 million employed and 4 million unemployed, the labour force is 44 million. Unemployment rate = (4m / 44m) × 100 = 9.1%.

示例：某国就业人口为 4000 万，失业人口为 400 万，则劳动力为 4400 万。失业率 = (400万 / 4400万) × 100 = 9.1%。

8. Inflation Rate | 通货膨胀率

Inflation is the sustained rise in the general price level. The rate is most commonly measured using the Consumer Price Index (CPI).

通货膨胀是指物价总水平的持续上涨。通货膨胀率最常用消费者价格指数 (CPI) 来衡量。

Inflation Rate = [(CPI_{current year} – CPI_{previous year}) / CPI_{previous year}] × 100

通货膨胀率 = [(当年 CPI – 上年 CPI) / 上年 CPI] × 100

If the CPI rises from 110 to 115, the inflation rate is (5/110) × 100 ≈ 4.55%. Deflation would be recorded if the rate is negative. The CPI tracking a typical ‘basket’ of goods and services is updated regularly.

如果 CPI 从 110 升至 115，通货膨胀率就是 (5/110) × 100 ≈ 4.55%。如果该比率为负，则表示通货紧缩。CPI 追踪一篮子典型商品和服务的价格，并被定期更新。

Example: The CPI was 120 in Year 1 and 126 in Year 2. Inflation rate = [(126 – 120) / 120] × 100 = 5%.

示例：第 1 年 CPI 为 120，第 2 年为 126。通货膨胀率 = [(126 – 120) / 120] × 100 = 5%。

9. Economic Growth and GDP | 经济增长与 GDP

Economic growth is measured by the increase in a country’s real Gross Domestic Product (GDP) over time. GDP per capita is often used to compare living standards.

经济增长通常通过一国实际国内生产总值 (GDP) 随时间的变化来衡量。人均 GDP 常被用来比较生活水平。

Economic Growth Rate = [(GDP_{current year} – GDP_{previous year}) / GDP_{previous year}] × 100

经济增长率 = [(当年 GDP – 上年 GDP) / 上年 GDP] × 100

You must use real GDP (adjusted for inflation) to get the true growth figure. Nominal GDP does not remove the effect of price changes.

你必须使用实际 GDP（剔除通货膨胀影响）才能得到真实的增长数据。名义 GDP 并没有消除价格变动的影响。

GDP per Capita = GDP / Population

人均 GDP = GDP / 人口

Example: Real GDP grew from $500 billion to $520 billion. Growth rate = (20/500) × 100 = 4%. If the population is 50 million, GDP per capita = $520 billion / 50m = $10,400.

示例：实际 GDP 从 5000 亿美元增长到 5200 亿美元。经济增长率 = (20/500) × 100 = 4%。若人口为 5000 万，人均 GDP = 5200 亿 / 5000 万 = 10400 美元。

10. Terms of Trade and Exchange Rates | 贸易条件与汇率

The terms of trade show the ratio between a country’s export prices and its import prices. An improvement in the terms of trade means the country can buy more imports with the same volume of exports.

贸易条件反映了一国出口价格与进口价格之间的比率。贸易条件的改善意味着该国用同样数量的出口产品可以换回更多的进口产品。

Terms of Trade = (Index of Export Prices / Index of Import Prices) × 100

贸易条件 = (出口价格指数 / 进口价格指数) × 100

An increase in the index (e.g., from 100 to 105) represents an improvement. A decrease means a deterioration. A rise in export prices or a fall in import prices improves the terms of trade.

指数的上升（如从 100 升至 105）代表改善。下降则代表恶化。出口价格的上升或进口价格的下降都会改善贸易条件。

Exchange rate movements can also be expressed as a percentage change, helpful when analysing appreciation and depreciation.

汇率的变动也可以表示为百分比变化，这有助于分析货币升值和贬值。

% Change in Exchange Rate = [(New Rate – Old Rate) / Old Rate] × 100

汇率变动百分比 = [(新汇率 – 旧汇率) / 旧汇率] × 100

Example (trade): Export price index = 120, import price index = 100. Terms of trade = (120/100) × 100 = 120. This means export prices have risen 20% relative to import prices, an improvement from the base year.

示例（贸易）：出口价格指数 = 120，进口价格指数 = 100。贸易条件 = (120/100) × 100 = 120。这表明出口价格相较于进口价格上升了 20%，比基期有所改善。

Example (exchange): The dollar / pound rate moves from $1.20 to $1.32 for £1. The pound has appreciated. % change = [(1.32 – 1.20) / 1.20] × 100 = 10%.

示例（汇率）：美元兑英镑汇率从 1 英镑兑 1.20 美元变动至 1.32 美元。英镑升值了。变动百分比 = [(1.32 – 1.20) / 1.20] × 100 = 10%。

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GCSE CIE Economics: Formula Summary Handbook | CIE GCSE 经济学：公式汇总手册