📚 IGCSE Edexcel Economics: Formula Summary Handbook | 爱德思IGCSE经济学公式汇总手册
The IGCSE Edexcel Economics course requires students to apply a range of formulas to analyse markets, business performance and the wider economy. This handbook brings together every essential formula, from elasticities and break‑even analysis to profitability ratios and macroeconomic indicators. Each section explains the formula, shows how to use it and reinforces understanding with bilingual commentary.
IGCSE 爱德思经济学课程要求学生运用一系列公式来分析市场、企业表现以及整体经济。本手册汇集了所有必考公式，涵盖弹性、盈亏平衡分析、盈利能力比率和宏观经济指标。每个部分都会解释公式、展示用法，并通过双语讲解巩固理解。
1. Price Elasticity of Demand (PED) | 需求价格弹性
Price elasticity of demand (PED) measures how responsive the quantity demanded of a good is to a change in its price. It is calculated using the percentage changes in quantity demanded and price.
需求价格弹性（PED）衡量一种商品的需求量对其价格变化的反应程度。计算时使用需求量变动百分比与价格变动百分比。
PED = (% Δ Quantity Demanded) ÷ (% Δ Price)
The value of PED is usually negative, because price and quantity demanded move in opposite directions, but the minus sign is often ignored. If the numerical value is greater than 1, demand is price elastic; if less than 1, it is price inelastic; if exactly 1, it is unit elastic.
PED 的值通常为负，因为价格与需求量反向变动，但实际使用时往往忽略负号。如果数值大于 1，需求是富有价格弹性的；小于 1 则是缺乏弹性；等于 1 则为单位弹性。
For example, if a 10% rise in the price of a luxury watch causes a 25% fall in quantity demanded, PED = -25% ÷ 10% = -2.5, so demand is elastic.
例如，若一款奢侈手表的价格上涨 10% 导致需求量下降 25%，PED = -25% ÷ 10% = -2.5，需求是富有弹性的。
2. Price Elasticity of Supply (PES) | 供给价格弹性
Price elasticity of supply (PES) measures the responsiveness of quantity supplied to a change in price. It is always positive, as price and quantity supplied move in the same direction.
供给价格弹性（PES）衡量供给量对价格变化的反应程度。它总是正值，因为价格与供给量同方向变动。
PES = (% Δ Quantity Supplied) ÷ (% Δ Price)
When PES is greater than 1, supply is price elastic; when less than 1, supply is price inelastic; equal to 1 means unit elastic supply. Elasticity of supply depends largely on the time period and the flexibility of production factors.
当 PES 大于 1 时，供给富有弹性；小于 1 时缺乏弹性；等于 1 时为单位弹性。供给弹性主要取决于时间周期和生产要素的灵活性。
For instance, a technology firm that can quickly increase output might have a PES of 2.5, while a farmer waiting for crops to grow has a much lower PES in the short run.
例如，能快速增产的科技公司可能拥有 2.5 的 PES，而等待庄稼生长的农民在短期内 PES 要低得多。
3. Income Elasticity of Demand (YED) | 需求收入弹性
Income elasticity of demand (YED) shows how demand for a product changes as consumer incomes change. It helps classify goods as normal or inferior.
需求收入弹性（YED）显示消费者收入变动时产品需求如何变化。它有助于将商品划分为正常品或劣等品。
YED = (% Δ Demand) ÷ (% Δ Income)
A positive YED means the good is a normal good; if YED is greater than 1, it is a luxury good with income‑elastic demand. A negative YED indicates an inferior good, where demand falls as incomes rise.
YED 为正表示该商品是正常品；若 YED 大于 1，则为奢侈品，收入弹性需求较大。YED 为负表示劣等品，收入上升时需求反而下降。
For example, if incomes rise by 5% and demand for bus travel falls by 8%, YED = -8% ÷ 5% = -1.6, meaning bus travel is an inferior good.
例如，若收入增长 5%，公交车出行需求下降 8%，YED = -8% ÷ 5% = -1.6，说明公交车出行是劣等品。
4. Cross Elasticity of Demand (XED) | 需求交叉弹性
Cross elasticity of demand (XED) measures how the demand for one good is affected by a price change in another good. It identifies substitutes and complements.
需求交叉弹性（XED）衡量一种商品的需求受另一种商品价格变化影响的程度。它可以识别替代品和互补品。
XED = (% Δ Demand for Good A) ÷ (% Δ Price of Good B)
If XED is positive, the two goods are substitutes; if negative, they are complements. A value close to zero suggests the goods are unrelated. The larger the absolute value, the stronger the relationship.
若 XED 为正，两种商品为替代品；若为负，则为互补品。数值接近零表明商品不相关。绝对值越大，关系越强。
For instance, a 10% rise in the price of coffee might increase demand for tea by 15%. XED = +15% ÷ +10% = +1.5, so tea and coffee are close substitutes.
例如，咖啡价格上涨 10% 可能使茶叶需求增加 15%。XED = +15% ÷ +10% = +1.5，因此茶叶和咖啡是密切的替代品。
5. Total Revenue, Total Cost and Profit | 总收入、总成本与利润
Total revenue (TR) is the income a firm receives from selling its products. It is simply price multiplied by quantity sold.
总收入（TR）是企业销售产品所获得的收入。它等于价格乘以销售数量。
Total Revenue = Price × Quantity
Total cost (TC) includes all the expenses of production. It is the sum of fixed costs (FC) and total variable costs (TVC). Variable cost per unit multiplied by quantity gives TVC.
总成本（TC）包括所有生产费用。它是固定成本（FC）与总可变成本（TVC）之和。单位可变成本乘以产量得出 TVC。
Total Cost = Fixed Cost + Total Variable Cost
Total Variable Cost = Variable Cost per Unit × Quantity
Profit is the difference between total revenue and total cost.
利润是总收入与总成本之差。
Profit = Total Revenue − Total Cost
If a firm sells 500 units at £30 each, TR = £15,000. If fixed costs are £4,000 and variable cost per unit is £18, TVC = 500 × £18 = £9,000. TC = £13,000. Profit = £15,000 − £13,000 = £2,000.
若一家企业以每件 30 英镑的价格出售 500 件产品，TR = 15000 英镑。若固定成本为 4000 英镑，单位可变成本为 18 英镑，TVC = 500 × 18 = 9000 英镑。TC = 13000 英镑。利润 = 15000 − 13000 = 2000 英镑。
6. Break‑even Analysis | 盈亏平衡分析
Break‑even analysis identifies the level of output at which total revenue equals total cost, so the firm makes neither a profit nor a loss. Key formulas are contribution per unit and break‑even output.
盈亏平衡分析确定总收入等于总成本时的产出水平，此时企业既不盈利也不亏损。关键公式包括单位贡献和盈亏平衡产量。
Contribution per Unit = Selling Price − Variable Cost per Unit
Contribution per unit shows how much each unit sold contributes towards fixed costs and, after covering them, towards profit.
单位贡献表示每销售一件产品能为固定成本做多少贡献，在抵消固定成本后则贡献利润。
Break‑even Output = Fixed Costs ÷ Contribution per Unit
Once the break‑even point is known, a business can set sales targets. For example, if fixed costs are £20,000, selling price is £50 and variable cost per unit is £30, contribution per unit is £20. Break‑even output = £20,000 ÷ £20 = 1,000 units.
知道了盈亏平衡点，企业便可以设定销售目标。例如，假设固定成本为 20000 英镑，售价为 50 英镑，单位可变成本为 30 英镑，单位贡献为 20 英镑。盈亏平衡产量 = 20000 ÷ 20 = 1000 件。
7. Cash Flow and Liquidity | 现金流与流动性
Net cash flow shows the difference between cash inflows and cash outflows over a period. It is essential for managing liquidity.
净现金流表示一个时期内现金流入与现金流出的差额。这对流动性管理至关重要。
Net Cash Flow = Cash Inflows − Cash Outflows
The closing balance for a period is calculated by adding net cash flow to the opening balance.
期末余额的计算方式是将净现金流加上期初余额。
Closing Balance = Opening Balance + Net Cash Flow
Liquidity ratios measure a firm’s ability to meet short‑term obligations. The current ratio compares current assets to current liabilities.
流动性比率衡量企业偿还短期债务的能力。流动比率将流动资产与流动负债进行比较。
Current Ratio = Current Assets ÷ Current Liabilities
The acid test ratio (also called quick ratio) is a stricter measure, excluding inventory from current assets. Inventory may not be quickly converted to cash.
速动比率（又称酸性测试比率）是更严格的衡量标准，将存货从流动资产中剔除。存货可能无法快速变现。
Acid Test Ratio = (Current Assets − Inventory) ÷ Current Liabilities
A current ratio of 1.5:1 and an acid test ratio of 0.9:1 are often seen as healthy, though acceptable values vary across industries.
流动比率为 1.5:1、速动比率为 0.9:1 通常被视为健康水平，但不同行业可接受的值有所不同。
8. Profitability Ratios | 盈利能力比率
Profitability ratios assess how effectively a business converts revenue into profit. The gross profit margin focuses on trading operations before overheads.
盈利能力比率评估企业将收入转化为利润的效率。毛利率重点关注扣除间接费用之前的贸易运营。
Gross Profit Margin (%) = (Gross Profit ÷ Revenue) × 100
Gross profit is revenue minus cost of goods sold. A higher margin indicates stronger pricing power or lower production costs.
毛利润是收入减去销售成本。较高的毛利率表明更强的定价能力或更低的生产成本。
The net profit margin takes all expenses into account, showing the percentage of revenue remaining as net profit.
净利润率考虑了所有费用，显示收入中以净利润形式留下的百分比。
Net Profit Margin (%) = (Net Profit ÷ Revenue) × 100
For example, a firm with revenue of £200,000 and a net profit of £30,000 has a net profit margin of (30,000 ÷ 200,000) × 100 = 15%.
例如，一家企业收入为 200000 英镑，净利润为 30000 英镑，其净利润率 = (30000 ÷ 200000) × 100 = 15%。
9. Return on Capital Employed (ROCE) and Average Rate of Return (ARR) | 已用资本回报率与平均回报率
ROCE measures how efficiently a business uses its long‑term capital to generate profit. It is a key indicator for investors.
ROCE 衡量企业利用长期资本创造利润的效率。它是投资者关注的关键指标。
ROCE (%) = (Net Profit ÷ Capital Employed) × 100
Capital employed is often taken as total equity plus non‑current liabilities, or total assets minus current liabilities. A higher ROCE suggests more effective use of capital.
已用资本通常指总权益加非流动负债，或总资产减去流动负债。ROCE 越高，表明资本运用越有效。
The average rate of return (ARR) helps evaluate investment projects by comparing average annual profit to the initial investment cost.
平均回报率（ARR）通过比较平均年利润与初始投资成本来评估投资项目。
ARR (%) = (Average Annual Profit ÷ Initial Investment) × 100
If a project costs £50,000 and generates total profits of £80,000 over 4 years, the average annual profit is £80,000 ÷ 4 = £20,000. ARR = (20,000 ÷ 50,000) × 100 = 40%.
若一个项目成本为 50000 英镑，4 年间产生总利润 80000 英镑，平均年利润为 80000 ÷ 4 = 20000 英镑。ARR = (20000 ÷ 50000) × 100 = 40%。
10. Macroeconomic Indicators: GDP, Growth, Inflation and Unemployment | 宏观经济指标：GDP、增长、通胀与失业
GDP per capita gives an average income per person and is widely used to compare living standards across countries.
人均 GDP 提供每人平均收入，广泛用于比较各国生活水平。
GDP per Capita = Total GDP ÷ Population
The economic growth rate measures how much a country’s output has increased from one period to the next.
经济增长率衡量一国产出从一个时期到下一个时期增加了多少。
Economic Growth Rate (%) = (Change in GDP ÷ Original GDP) × 100
Inflation is measured using a price index such as the Consumer Price Index (CPI). The inflation rate is the percentage change in the index.
通货膨胀通过消费者价格指数（CPI）等价格指数来衡量。通胀率即该指数的百分比变化。
Inflation Rate (%) = (Change in CPI ÷ Original CPI) × 100
The unemployment rate shows the proportion of the labour force that is actively seeking work but unable to find it.
失业率显示了劳动力中积极寻找工作但未能找到的人口比例。
Unemployment Rate (%) = (Number of Unemployed ÷ Labour Force) × 100
For example, if a country’s GDP rises from $500 billion to $530 billion, the growth rate is (30 ÷ 500) × 100 = 6%.
例如，若某国 GDP 从 5000 亿美元上升至 5300 亿美元，增长率 = (300 ÷ 5000) × 100 = 6%。（注意数值调整，原文可用比例。）
11. Exchange Rates | 汇率
Exchange rates show how much one currency is worth in terms of another. Simple currency conversions are tested in IGCSE Economics. To convert an amount into a foreign currency, multiply by the exchange rate.
汇率表示一种货币以另一种货币衡量时的价值。IGCSE 经济学考试中会考查简单的货币换算。要将一笔金额换算成外币，乘以汇率即可。
Amount in Foreign Currency = Amount in Home Currency × Exchange Rate
If the exchange rate is £1 = $1.30, then £200 would be converted to $200 × 1.30 = $260. To convert back, divide by the same rate.
若汇率为 1 英镑 = 1.30 美元，则 200 英镑可兑换为 200 × 1.30 = 260 美元。换算回来时除以相同汇率。
Changes in exchange rates affect the prices of exports and imports, and therefore the trade balance. A weaker home currency makes exports cheaper and imports dearer.
汇率变动会影响进出口价格，进而影响贸易平衡。本币贬值会使出口变得更便宜，进口变得更昂贵。
12. Formula Summary Table | 公式汇总表
The table below lists all the important formulas for IGCSE Edexcel Economics in one place. Use it for quick revision.
下表汇总了 IGCSE 爱德思经济学的所有重要公式，方便快速复习。
| Formula Name | 公式名称 | Formula | 公式 | Key Use | 主要用途 |
|---|---|---|
| PED | 需求价格弹性 | (% Δ QD) ÷ (% Δ Price) | Pricing decisions |
| PES | 供给价格弹性 | (% Δ QS) ÷ (% Δ Price) | Supply responsiveness |
| YED | 需求收入弹性 | (% Δ Demand) ÷ (% Δ Income) | Classifying normal/inferior goods |
| XED | 需求交叉弹性 | (% Δ Demand for A) ÷ (% Δ Price of B) | Substitutes/complements |
| Total Revenue | 总收入 | Price × Quantity | Revenue analysis |
| Total Cost | 总成本 | FC + TVC | Cost control |
| Profit | 利润 | TR − TC | Performance measure |
| Contribution per Unit | 单位贡献 | Selling Price − VC per Unit | Break‑even and decision making |
| Break‑even Output | 盈亏平衡产量 | FC ÷ Contribution per Unit | Target setting |
| Net Cash Flow | 净现金流 | Cash Inflows − Cash Outflows | Liquidity management |
| Closing Balance | 期末余额 | Opening Balance + Net Cash Flow | Cash flow forecasting |
| Current Ratio | 流动比率 | Current Assets ÷ Current Liabilities | Short‑term solvency |
| Acid Test Ratio | 速动比率 | (Current Assets − Inventory) ÷ Current Liabilities | Stricter liquidity test |
| Gross Profit Margin | 毛利率 | (Gross Profit ÷ Revenue) × 100 | Profitability from trading |
| Net Profit Margin | 净利润率 | (Net Profit ÷ Revenue) × 100 | Overall cost efficiency |
| ROCE | 已用资本回报率 | (Net Profit ÷ Capital Employed) × 100 | Investment returns |
| ARR | 平均回报率 | (Average Annual Profit ÷ Initial Investment) × 100 | Project appraisal |
| GDP per Capita | 人均 GDP | GDP ÷ Population | Living standards comparison |
| Economic Growth | 经济增长率 | (Δ GDP ÷ Original GDP) × 100 | Economic performance |
| Inflation Rate | 通胀率 | (Δ CPI ÷ Original CPI) × 100 | Price stability |
| Unemployment Rate | 失业率 | (Unemployed ÷ Labour Force) × 100 | Labour market health |
| Currency Conversion | 货币兑换 | Home Currency × Exchange Rate | International trade and travel |
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