📚 Year 11 Edexcel Economics: Formula & Theorem Quick Reference Handbook | 十一年级爱德思经济：公式定理速查手册
This quick reference handbook brings together every essential formula, theorem and key definition you need for Year 11 Edexcel Economics. Whether you are calculating elasticities, interpreting index numbers or analysing business costs, the paired English and Chinese explanations will help you master each tool quickly and confidently.
这本速查手册汇集了十一年级爱德思经济课程中每一个必学的公式、定理和关键定义。无论你是在计算弹性、解读指数数字还是分析企业成本，中英对照的讲解都能帮助你快速而自信地掌握每一个工具。
1. Percentage Changes and Key Calculations | 百分比变化与基本计算
Many economic formulas rely on the percentage change between an original value and a new value. The standard expression is: % change = (New Value − Original Value) ÷ Original Value × 100.
许多经济公式都依赖于原值和新值之间的百分比变化。标准表达式为：% 变化 = (新值 − 原值) ÷ 原值 × 100。
Always identify the original number correctly before applying the formula. A positive result indicates an increase, while a negative result shows a decrease. Economists use this tool for demand, supply, inflation, GDP and many other indicators.
应用公式前务必准确识别原值。正值表明增加，负值表明减少。经济学家将这一工具用于需求、供给、通胀、GDP 及许多其他指标。
2. Demand and Supply: The Laws | 需求与供给定律
The Law of Demand states that, ceteris paribus, as the price of a good rises, the quantity demanded falls. This inverse relationship is driven by the income effect and substitution effect.
需求定律指出，在其他条件不变时，商品价格上升，需求量下降。这一反向关系由收入效应和替代效应共同驱动。
The Law of Supply states that, ceteris paribus, as the price of a good rises, the quantity supplied increases. Producers are willing to offer more when the price is higher because profitability improves.
供给定律指出，在其他条件不变时，商品价格上升，供给量增加。更高的价格改善了盈利性，因此生产者愿意提供更多。
Demand curve: P ↑ → Qd ↓ | Supply curve: P ↑ → Qs ↑
3. Price Elasticity of Demand (PED) | 需求价格弹性
Price Elasticity of Demand measures the responsiveness of quantity demanded to a change in price. The core formula is:
需求价格弹性衡量需求量对价格变化的反应程度。核心公式为：
PED = %Δ Quantity Demanded ÷ %Δ Price
If PED > 1, demand is price elastic: a small price change causes a proportionally larger change in quantity demanded. If PED < 1, demand is price inelastic. If PED = 1, it is unit elastic. PED = ∞ signals perfectly elastic demand; PED = 0 signals perfectly inelastic demand.
若 PED > 1，需求富有价格弹性：微小的价格变动引起需求量更大幅度的变动。若 PED < 1，需求缺乏价格弹性。若 PED = 1，则为单位弹性。PED = ∞ 表示完全弹性需求；PED = 0 表示完全无弹性需求。
| PED Value | Classification | 分类 | Effect on Total Revenue |
|---|---|---|
| > 1 | Elastic | 富有弹性 | Price cut raises TR; price rise lowers TR |
| < 1 | Inelastic | 缺乏弹性 | Price cut lowers TR; price rise raises TR |
| = 1 | Unit elastic | 单位弹性 | TR unchanged when price changes |
PED is always expressed as a positive number although the underlying ratio is negative due to the law of demand. Edexcel uses the absolute value in most questions.
尽管受需求定律影响比值本为负数，PED 通常表示为正数。爱德思考试中多数题目使用绝对值。
4. Income Elasticity of Demand (YED) | 需求收入弹性
Income Elasticity of Demand measures how quantity demanded responds to a change in consumers’ income. The formula is:
需求收入弹性衡量需求量对消费者收入变动的反应程度。公式为：
YED = %Δ Quantity Demanded ÷ %Δ Income
A positive YED identifies a normal good. If YED > 1, the good is a luxury (income-elastic). A negative YED identifies an inferior good, where demand falls as income rises. YED between 0 and 1 indicates a necessity.
YED 为正表明商品是正常品。若 YED > 1，该商品为奢侈品（富有收入弹性）。YED 为负表明商品是低档品，收入上升时需求反而下降。YED 在 0 至 1 之间则显示为必需品。
| YED Value | Good Type | 商品类型 | Example |
|---|---|---|
| > 1 | Luxury | 奢侈品 | Overseas holidays, designer clothes |
| 0 – 1 | Necessity | 必需品 | Basic food, toothpaste |
| < 0 | Inferior good | 低档品 | Generic bread, second-hand clothes |
5. Price Elasticity of Supply (PES) | 供给价格弹性
Price Elasticity of Supply measures how responsive quantity supplied is to a price change. The formula is:
供给价格弹性衡量供给量对价格变动的反应程度。公式为：
PES = %Δ Quantity Supplied ÷ %Δ Price
PES is always positive because of the law of supply. PES > 1 indicates elastic supply; PES < 1 indicates inelastic supply. Key determinants include time period, spare production capacity, availability of raw materials and ease of storage.
由于供给定律，PES 始终为正。PES > 1 表示供给富有弹性；PES < 1 表示供给缺乏弹性。关键决定因素包括考察的时间长度、闲置产能、原材料的可得性以及储存的难易程度。
6. Consumer Price Index (CPI) and Inflation | 消费者价格指数与通货膨胀
A price index tracks the cost of a fixed basket of goods over time. The base year is always given an index number of 100. The formula for the index is:
价格指数追踪固定一篮子商品随时间推移的成本。基年的指数值恒为 100。指数公式为：
Price Index = (Cost of Basket in Current Year ÷ Cost of Basket in Base Year) × 100
Inflation rate is then calculated as the percentage change in a price index (usually CPI) between two periods:
随后，通胀率计算为两期之间价格指数（通常为 CPI）的百分比变化：
Inflation Rate = [(Current Year Index − Previous Year Index) ÷ Previous Year Index] × 100
Low and stable inflation is one of the government’s key macroeconomic objectives in the UK, often targeted at 2% by the Bank of England.
低且稳定的通胀是英国政府的关键宏观经济目标之一，英格兰银行通常将目标定为 2%。
7. Unemployment Rate | 失业率
The unemployment rate expresses the unemployed as a percentage of the labour force. Two important definitions from the UK’s Office for National Statistics are used: the Claimant Count and the Labour Force Survey (ILO measure).
失业率将失业人口表示为劳动力的百分比。英国国家统计局使用两个重要定义：申领人数统计与劳动力调查（ILO 口径）。
Unemployment Rate = (Number of Unemployed ÷ Labour Force) × 100
The labour force includes all people who are either employed or actively seeking work. Students, retirees and those not seeking work are not counted in the labour force. Governments aim for low unemployment, often referred to as full employment, where anyone willing and able to work can find a job.
劳动力包括所有已就业或正在积极寻找工作的人。学生、退休人员和不愿工作者不计入劳动力。政府追求低失业率，常称为充分就业，即任何一个愿意且有能力工作的人都能找到工作。
8. Economic Growth and GDP | 经济增长与国内生产总值
Gross Domestic Product (GDP) measures the total value of all goods and services produced in an economy over a period. Economic growth is typically measured by the percentage change in real GDP.
国内生产总值（GDP）衡量一个经济体在一定时期内所生产的所有最终商品和服务的总价值。经济增长通常以实际 GDP 的百分比变化来衡量。
Real GDP Growth = [(Real GDP Year 2 − Real GDP Year 1) ÷ Real GDP Year 1] × 100
Real GDP strips out the effect of inflation so that we measure changes in output rather than prices. Another useful tool is GDP per capita:
实际 GDP 剔除了通胀的影响，以便衡量产出而非价格的变化。另一个有用工具是人均 GDP：
GDP per Capita = Real GDP ÷ Population
This gives a rough guide to living standards, although it does not account for income distribution or well-being.
它大致反映了生活水平，但并未计入收入分配或福利状况。
9. Business Costs, Revenue and Profit | 企业成本、收益与利润
Total revenue (TR) is the income a firm receives from selling its output. Total cost (TC) is the sum of all production expenses. Profit is the key incentive for entrepreneurs.
总收益（TR）是企业销售产出所获得的收入。总成本（TC）是所有生产开支的总和。利润是企业家最核心的激励。
Total Revenue = Price × Quantity Sold
Total Cost = Total Fixed Cost + Total Variable Cost
Profit = Total Revenue − Total Cost
Average cost (unit cost) is calculated as Total Cost ÷ Output. A firm makes a profit when price exceeds average cost; it breaks even when price equals average cost.
平均成本（单位成本）计算公式为：总成本 ÷ 产出。当价格高于平均成本时企业盈利；价格等于平均成本时达到盈亏平衡。
10. Productivity | 生产率
Productivity measures how efficiently inputs are turned into outputs. Labour productivity is the most common measure at GCSE.
生产率衡量投入转化为产出的效率。GCSE 阶段最常用的是劳动生产率。
Labour Productivity = Total Output ÷ Number of Workers
Higher productivity can lower average costs, increase wages and improve international competitiveness. Investment in technology, training and better management are ways to raise productivity.
更高的生产率能降低平均成本、提高工资并增强国际竞争力。投资于技术、培训和优化管理是提升生产率的途径。
11. Tax Revenue and Government Budget | 税收与政府预算
Governments collect tax revenue to fund public services. The total revenue from a specific tax can be estimated by multiplying the tax per unit by the quantity sold.
政府征税以资助公共服务。某税种的总收入可通过单位税额乘以销售数量来估算。
Tax Revenue = Tax per Unit × Quantity Sold
A government budget balance compares revenue with spending. A budget surplus occurs when revenue > spending; a deficit when spending > revenue. The formula for the budget position is:
政府预算平衡比较收入与支出。当收入大于支出时出现预算盈余；支出大于收入时出现赤字。预算状况公式为：
Budget Balance = Total Government Revenue − Total Government Spending
12. Exchange Rates and Currency Conversion | 汇率与货币兑换
An exchange rate is the price of one currency expressed in terms of another. For example, if GBP/USD = 1.25, one pound buys 1.25 US dollars. Converting between currencies uses two straightforward rules:
汇率是用一种货币表示的另一种货币的价格。例如，若 GBP/USD = 1.25，则 1 英镑可购买 1.25 美元。货币兑换遵循两条简单规则：
To convert from home currency to foreign currency, multiply by the exchange rate: Amount in USD = Amount in GBP × Exchange Rate (GBP/USD).
将本币兑换为外币时，乘以汇率：美元金额 = 英镑金额 × 汇率 (GBP/USD)。
To convert back from foreign currency to home currency, divide by the exchange rate: Amount in GBP = Amount in USD ÷ Exchange Rate.
将外币兑回本币时，除以汇率：英镑金额 = 美元金额 ÷ 汇率。
A weaker pound means exports become cheaper and imports become dearer; a stronger pound has the opposite effect.
英镑走弱意味着出口更便宜而进口更贵；英镑走强则效果相反。
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