📚 Year 11 OCR Economics: Quick Reference to Formulas and Theorems | OCR 经济公式定理速查手册
This handbook presents the essential formulas and economic laws you need for the OCR GCSE Economics exam. Each entry is explained in English with a mirrored Chinese translation, helping you consolidate understanding and apply concepts confidently in data-response and extended-writing questions.
本手册整理了OCR GCSE经济学考试必备的核心公式与定理。每个条目均提供中英文对照解释，帮助你巩固理解，并在数据分析题和论述题中自信运用。
1. Price Elasticity of Demand (PED) | 需求价格弹性
Price elasticity of demand measures how much the quantity demanded of a good responds to a change in its price. It is a key indicator of consumer responsiveness and is vital for businesses when setting prices.
需求价格弹性衡量一种商品的需求量对其价格变化的反应程度。它是反映消费者敏感度的重要指标，也是企业定价时的重要依据。
PED = % Change in Quantity Demanded / % Change in Price
需求价格弹性 = 需求量变化百分比 / 价格变化百分比
- % Change = [(New – Old) / Old] × 100% — 变化百分比 = [(新值 – 旧值) / 旧值] × 100%
- If |PED| > 1, demand is price elastic. — 若|PED| > 1，需求富有价格弹性。
- If |PED| < 1, demand is price inelastic. — 若|PED| < 1，需求缺乏价格弹性。
- If |PED| = 1, demand is unit elastic. — 若|PED| = 1，需求具有单位弹性。
2. Price Elasticity of Supply (PES) | 供给价格弹性
Price elasticity of supply captures the responsiveness of quantity supplied to a change in price. It depends on the flexibility of production and the time period considered.
供给价格弹性反映供给量对价格变化的反应程度，取决于生产的灵活性和所考察的时间段。
PES = % Change in Quantity Supplied / % Change in Price
供给价格弹性 = 供给量变化百分比 / 价格变化百分比
- Any PES value greater than 0 indicates a normal upward-sloping supply curve. — 任何大于0的PES值均表示正常向上倾斜的供给曲线。
- PES > 1: elastic supply (producers can adjust output quickly). — PES > 1：供给富有弹性，生产者能够迅速调整产量。
- PES < 1: inelastic supply (output is difficult to change in the short run). — PES < 1：供给缺乏弹性，短期内产量难以改变。
3. Income Elasticity of Demand (YED) | 需求收入弹性
Income elasticity of demand shows how demand changes as consumer incomes change. It helps classify goods as normal or inferior and predicts the impact of economic growth on sectors.
需求收入弹性表明需求量如何随消费者收入变化而变动，有助于区分正常品和劣质品，并预测经济增长对各部门的影响。
YED = % Change in Quantity Demanded / % Change in Income
需求收入弹性 = 需求量变化百分比 / 收入变化百分比
- YED > 0: normal good (demand rises with income). — YED > 0：正常品，收入增加时需求上升。
- YED < 0: inferior good (demand falls as income rises). — YED < 0：劣质品，收入增加时需求下降。
- 0 < YED < 1: necessity; YED > 1: luxury. — 0 < YED < 1：必需品；YED > 1：奢侈品。
4. Cross Elasticity of Demand (XED) | 需求交叉弹性
Cross elasticity of demand measures how the demand for one good reacts to a price change in another good. It identifies substitutes and complements in consumption.
需求交叉弹性衡量一种商品的需求量对另一种商品价格变动的反应，用以识别消费品中的替代品和互补品。
XED = % Change in Qd of Good A / % Change in Price of Good B
商品A的需求交叉弹性 = A商品需求量变化% / B商品价格变化%
- XED > 0: substitutes (e.g. tea and coffee). — XED > 0：替代品，如茶和咖啡。
- XED < 0: complements (e.g. printers and ink cartridges). — XED < 0：互补品，如打印机和墨盒。
- XED ≈ 0: unrelated goods. — XED ≈ 0：不相关商品。
5. Cost, Revenue and Profit Formulas | 成本、收入与利润公式
Understanding cost and revenue structures is fundamental to business economics. These formulas allow a firm to calculate its efficiency and profit at any level of output.
理解成本与收入结构是企业经济学的基础。这些公式能帮助企业在任意产量水平上计算效率和利润。
| English Formula | 中文公式 |
|---|---|
| Total Cost (TC) = Fixed Cost (FC) + Variable Cost (VC) | 总成本 = 固定成本 + 可变成本 |
| Average Total Cost (ATC) = TC / Quantity (Q) | 平均总成本 = 总成本 / 产量 |
| Average Fixed Cost (AFC) = FC / Q | 平均固定成本 = 固定成本 / 产量 |
| Average Variable Cost (AVC) = VC / Q | 平均可变成本 = 可变成本 / 产量 |
| Total Revenue (TR) = Price (P) × Quantity Sold (Q) | 总收益 = 价格 × 销售量 |
| Average Revenue (AR) = TR / Q = Price | 平均收益 = 总收益 / 销量 = 价格 |
| Profit = Total Revenue – Total Cost | 利润 = 总收益 – 总成本 |
6. Breakeven and Contribution | 盈亏平衡与边际贡献
Breakeven analysis identifies the output level at which a firm covers all its costs. Contribution helps determine how much each unit sold contributes toward fixed costs and profit.
盈亏平衡分析确定企业刚好弥补全部成本的产量水平。边际贡献则反映每售出一单位产品能为固定成本和利润做出的贡献。
Breakeven Output = Fixed Costs / (Price – Variable Cost per Unit)
盈亏平衡产量 = 固定成本 / (单价 – 单位可变成本)
Contribution per Unit = Selling Price – Variable Cost per Unit
单位边际贡献 = 销售单价 – 单位可变成本
- If TR = TC, the firm breaks even. — 当总收益 = 总成本时，企业实现盈亏平衡。
- Contribution must first cover fixed costs; any surplus is profit. — 边际贡献须先弥补固定成本，超出部分即为利润。
7. Market Structure and the Concentration Ratio | 市场结构与集中度比率
The concentration ratio measures the total market share held by the largest firms. It gives a quick indication of market power and the degree of competition. In OCR economics, a five-firm concentration ratio (CR5) is commonly used.
集中度比率衡量行业内最大几家企业所占市场份额的总和，是判断市场势力和竞争程度的快捷指标。OCR经济学中常用五企业集中度比率（CR5）。
CRₙ = Sum of market share of the top n firms (%)
CRₙ = 前n家企业市场份额之和（%）
- High CR5 (e.g. > 60%) suggests an oligopoly or monopoly. — 高CR5（如大于60%）表明寡头垄断或垄断市场。
- Low CR5 (e.g. < 40%) indicates a competitive market. — 低CR5（如小于40%）表明竞争性市场。
- It does not measure all dimensions of competition; qualitative factors also matter. — 集中度比率无法衡量竞争的所有维度，还需考虑定性因素。
8. Labour Market and Wage Differentials | 劳动力市场与工资差异
Wages are determined by the interaction of demand for labour and supply of labour. Diagrams help visualise equilibrium, and formulas like average wage and wage rate are basic accounting tools.
工资由劳动力需求与劳动力供给的相互作用决定。均衡图可直观展示，而平均工资和工资率等公式是基本的计量工具。
Average Weekly Wage = Total Wage Bill / Number of Workers
平均周薪 = 工资总额 / 劳动者人数
Factors affecting demand: productivity, product demand, cost of capital. Factors affecting supply: skills, migration, non-monetary benefits. These explain wage differentials between occupations.
影响劳动力需求的因素：生产率、产品需求、资本成本。影响劳动力供给的因素：技能、移民、非货币福利。这些可解释不同职业间的工资差异。
9. Macroeconomic Indicators | 宏观经济指标
National income, unemployment, and inflation are the three key performance indicators. Their formulas help students interpret economic data and government policy in the OCR exam.
国民收入、失业和通货膨胀是三大核心宏观经济指标。相关公式有助于学生在OCR考试中解读经济数据与政府政策。
Unemployment Rate = (Number Unemployed / Labour Force) × 100%
失业率 = (失业人数 / 劳动力总人数) × 100%
Inflation Rate via CPI = [(CPIₙ – CPIₙ₋₁) / CPIₙ₋₁] × 100%
通货膨胀率（消费者价格指数）= [(当期CPI – 上期CPI) / 上期CPI] × 100%
Real GDP per Capita = Real GDP / Population
人均实际国内生产总值 = 实际GDP / 人口数
Real values are adjusted for inflation using the base year, while nominal values are not. This distinction is critical when analysing living standards.
实际值已按基年剔除通胀影响，而名义值未作调整。在分析生活水平时，这一区别至关重要。
10. Exchange Rates and Balance of Payments | 汇率与国际收支
Exchange rates express the value of one currency in terms of another. They influence export competitiveness, import prices, and the current account balance.
汇率是用一种货币表示另一种货币的价格，会影响出口竞争力、进口价格和经常账户余额。
Currency Conversion: Amount in GBP × Exchange Rate = Amount in Foreign Currency
货币兑换：英镑金额 × 汇率 = 外币金额
- If GBP appreciates (exchange rate rises), exports become dearer and imports cheaper. — 若英镑升值（汇率上升），出口变贵，进口变便宜。
- If GBP depreciates, exports become cheaper and imports dearer. — 若英镑贬值，出口变便宜，进口变贵。
- goods + Balance of trade in services + Net primary income + Net secondary income. — 经常账户 = 货物贸易差额 + 服务贸易差额 + 初次收入净额 + 二次收入净额。
Published by TutorHao | Economics Revision Series | aleveler.com
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