📚 OCR GCSE Economics Formula & Theorem Quick-Reference Handbook | OCR 经济学公式定理速查手册
The OCR GCSE Economics exam tests your ability to apply key formulas, interpret data, and explain economic concepts. This quick-reference handbook compiles the essential formulas and theorems you need to master, organised by topic, with clear definitions and illustrative examples. Use it to revise efficiently and build confidence for your assessments.
OCR GCSE 经济学考试会考查关键公式的应用、数据解读和经济学概念解释。本速查手册按主题整理了必须掌握的核心公式与定理，并附有清晰定义和示例说明。高效备考，自信应考，从这里开始。
1. Basic Economic Problem & Opportunity Cost | 基本经济问题与机会成本
The fundamental economic problem arises because resources are scarce relative to unlimited wants. Every choice involves an opportunity cost — the value of the next best alternative forgone.
基本经济问题源于相对于无限欲望的资源稀缺性。任何选择都涉及机会成本——即所放弃的次优选项的价值。
Opportunity cost is not always monetary; it can be measured in time, satisfaction or output sacrificed. A simple way to express it is:
机会成本不一定是货币形式；它可以用时间、满足感或牺牲的产出来衡量。一个简单的表达是：
Opportunity Cost = Value of Next Best Alternative Forgone
For example, if a government spends £10 million on a new hospital, the opportunity cost could be the schools or roads not built with that same money.
例如，如果政府投入1000万英镑新建医院，机会成本可能就是放弃用这笔资金建造学校或道路。
2. Production Possibility Frontier (PPF) | 生产可能性边界（PPF）
The PPF shows the maximum combinations of two goods an economy can produce when all resources are fully and efficiently employed. Points inside the curve indicate inefficiency, while points outside are unattainable with current resources.
PPF 展示了一个经济体在所有资源得到充分有效利用时能够生产的两种商品的最大组合。曲线内侧的点代表低效率，曲线外侧的点在当前资源下无法达到。
The slope of the PPF is the marginal rate of transformation (MRT), which measures the opportunity cost of producing one more unit of a good.
PPF 的斜率是边际转换率（MRT），用来衡量多生产一单位某种产品的机会成本。
MRT = ΔY / ΔX
Where ΔY is the quantity of good Y given up and ΔX is the extra quantity of good X produced. A concave PPF illustrates increasing opportunity cost.
其中 ΔY 表示放弃的产品 Y 的数量，ΔX 表示额外生产的产品 X 的数量。凹向原点的 PPF 反映了递增的机会成本。
3. Elasticity of Demand & Supply | 需求与供给的弹性
Elasticity measures the responsiveness of quantity demanded or supplied to changes in price, income or related goods' prices. The four key elasticities are given below.
弹性衡量需求量或供给量对价格、收入或相关商品价格变动的反应程度。以下为四种关键弹性公式。
Price elasticity of demand (PED):
PED = % Change in Quantity Demanded / % Change in Price
Price elasticity of supply (PES):
PES = % Change in Quantity Supplied / % Change in Price
Income elasticity of demand (YED):
YED = % Change in Quantity Demanded / % Change in Income
Cross elasticity of demand (XED):
XED = % Change in Quantity Demanded of Good A / % Change in Price of Good B
The numerical values lead to different elasticity categories. For PED:
根据数值大小，弹性可分为不同类别。以需求价格弹性为例：
| PED Value | Elasticity Type | Meaning |
|---|---|---|
| > 1 | Price elastic | %ΔQd > %ΔP; total revenue moves with quantity |
| < 1 | Price inelastic | %ΔQd < %ΔP; total revenue moves with price |
| = 1 | Unit elastic | %ΔQd = %ΔP; total revenue unchanged |
| = 0 | Perfectly inelastic | Quantity demanded does not change with price |
| = ∞ | Perfectly elastic | Any price increase reduces quantity demanded to zero |
YED > 0 indicates a normal good; YED < 0 indicates an inferior good. XED > 0 for substitutes and XED < 0 for complements.
收入弹性 YED > 0 代表正常品；YED < 0 代表低档品。交叉弹性 XED > 0 代表替代品，XED < 0 代表互补品。
4. Costs, Revenue & Profit | 成本、收益与利润
Firms need to understand their cost structure and revenue streams to maximise profit. The key formulas are:
企业需要了解成本结构和收入来源才能实现利润最大化。关键公式如下：
Total Cost (TC):
TC = Total Fixed Cost (TFC) + Total Variable Cost (TVC)
Average Total Cost (ATC or AC):
ATC = TC / Quantity (Q)
Total Revenue (TR):
TR = Price (P) × Quantity Sold (Q)
Profit (or Loss):
Profit = TR - TC
quals zero, set TR = TC. For a single product, the break-even output can be calculated as:
要找到利润为零的盈亏平衡点，令 TR = TC。对于单一产品，盈亏平衡产量可按如下公式计算：
Break-even Output = TFC / (Price - Average Variable Cost)
The denominator (P - AVC) is known as the contribution per unit. It shows how much each unit sold contributes towards covering fixed costs after variable costs are paid.
分母（P - AVC）称为单位贡献利润，反映每销售一单位产品在支付变动成本后对回收固定成本的贡献额。
5. Market Equilibrium & Disequilibrium | 市场均衡与非均衡
Market equilibrium occurs at the price where quantity demanded equals quantity supplied. Algebraically:
市场均衡出现在需求量与供给量相等的价格水平上。代数表达为：
Qd = Qs
At any price above equilibrium, there is excess supply (surplus), putting downward pressure on price. At a price below equilibrium, excess demand (shortage) pushes price upward. The market-clearing price is the equilibrium price.
当价格高于均衡水平时，会出现超额供给（盈余），对价格产生下行压力；当价格低于均衡水平时，超额需求（短缺）推动价格上升。市场出清价格就是均衡价格。
d = 100 - 2P and supply is Qs = -20 + 4P, set them equal to solve for equilibrium P and Q.
当需求或供给发生移动时，可将新的函数式代入求解新的均衡。例如，需求函数为 Qd = 100 - 2P，供给函数为 Qs = -20 + 4P，令两者相等即可解出均衡价格与数量。
6. Government Intervention: Indirect Taxation & Subsidies | 政府干预：间接税与补贴
An indirect tax shifts the supply curve vertically upwards by the amount of the tax. The incidence (burden) is shared between consumers and producers depending on relative elasticities.
间接税使供给曲线向上垂直平移相当于税额的幅度。税收负担根据供需弹性的大小在消费者与生产者之间分摊。
Tax per unit = New equilibrium price paid by consumers - Price received by producers
Total tax revenue for the government is the per-unit tax multiplied by the new equilibrium quantity:
政府税收总收入等于单位税额乘以新的均衡数量：
Government Tax Revenue = Tax per unit × Q (post-tax)
Similarly, a subsidy shifts the supply curve downwards. The subsidy per unit is the difference between the price received by producers and the price paid by consumers. The total cost to the government is:
同样地，补贴使供给曲线向下平移。单位补贴额等于生产者收到的价格与消费者支付价格之差。政府总补贴成本为：
Total Subsidy Cost = Subsidy per unit × Q (post-subsidy)
7. Macroeconomic Objectives & Aggregates | 宏观经济目标与总量
Governments typically pursue low inflation, sustainable growth, low unemployment, and a balanced current account. Key formulas to measure these are:
政府通常追求低通胀、可持续增长、低失业和国际收支平衡。用以衡量这些目标的关键公式包括：
Gross Domestic Product (GDP) – expenditure approach:
GDP = C + I + G + (X - M)
where C = consumption, I = investment, G = government spending, X = exports, M = imports.
其中 C = 消费，I = 投资，G = 政府支出，X = 出口，M = 进口。
GDP per capita:
GDP per capita = GDP / Population
Inflation rate (using Consumer Price Index, CPI):
Inflation Rate = (CPI current year - CPI previous year) / CPI previous year × 100
Unemployment rate:
Unemployment Rate = (Number of Unemployed / Labour Force) × 100
Economic growth rate:
P Growth = (Real GDP current year - Real GDP previous year) / Real GDP previous year × 100
8. The Multiplier Effect | 乘数效应
The multiplier measures how much national income changes following an initial change in spending (injection). It depends on the marginal propensity to consume (MPC) or withdraw (MPW).
乘数用于衡量初始支出（注入量）变动所引发的国民收入总变动。它取决于边际消费倾向（MPC）或边际漏出倾向（MPW）。
Multiplier (k) = 1 / (1 - MPC) = 1 / MPW
(marginal propensity to save, tax, and import), a high MPW leads to a smaller multiplier.
由于 MPW = MPS + MPT + MPM（边际储蓄、税收和进口倾向），较高的 MPW 会导致较小的乘数。
The final change in national income is:
国民收入的最终变动为：
Δ National Income = k × Δ Injection
For example, if the MPC is 0.8, the multiplier is 1 / (1 - 0.8) = 5. An initial £100 million investment would ultimately raise national income by £500 million.
例如，若 MPC 为 0.8，则乘数为 1 / (1 - 0.8) = 5。一笔初始 1 亿英镑的投资最终将使国民收入增加 5 亿英镑。
9. Fiscal Policy & Budget Balance | 财政政策与预算平衡
The government's budget balance is the difference between its revenue (mainly taxes) and its expenditure. It can be a surplus, deficit, or balanced.
政府预算余额是指政府收入（主要是税收）与支出之间的差额，可以是盈余、赤字或平衡。
Budget Balance = Government Revenue - Government Spending
A positive balance is a fiscal surplus; a negative balance is a deficit. The structural budget position excludes cyclical effects and shows the underlying fiscal stance.
正余额代表财政盈余，负余额代表财政赤字。结构性预算余额剔除了周期性影响，用于反映潜在的财政立场。
Changes in tax rates or government spending are tools of fiscal policy used to influence aggregate demand. For example, a cut in income tax increases disposable income, raising consumption (C) in the GDP equation.
调整税率或政府支出是财政政策的工具，用来影响总需求。例如，降低个人所得税能增加可支配收入，从而提升 GDP 公式中的消费 C。
10. International Trade & Exchange Rates | 国际贸易与汇率
The exchange rate is the price of one currency expressed in terms of another. A change in the exchange rate affects export and import prices. The percentage change in the exchange rate is:
汇率是一种货币用另一种货币表示的价格。汇率变动会影响进出口价格。汇率变动百分比为：
% Change in Exchange Rate = (New Rate - Old Rate) / Old Rate × 100
For trade performance, the terms of trade index measures the relative price of exports to imports:
就贸易表现而言，贸易条件指数衡量出口相对进口的价格水平：
Terms of Trade Index = (Export Price Index / Import Price Index) × 100
An improvement in the terms of trade means a country can buy more imports with a given volume of exports. However, it may worsen the current account if export demand is price elastic.
贸易条件改善意味着用既定数量的出口可以购买更多进口品。但如果出口需求富有弹性，经常账户可能反而恶化。
11. Interest Rates & Monetary Policy | 利率与货币政策
Interest rates are a key tool of monetary policy, set by the central bank to influence borrowing, saving, and aggregate demand. The real interest rate adjusts for inflation:
利率是货币政策的关键工具，由中央银行设定以影响借贷、储蓄和总需求。实际利率扣除了通胀因素：
Real Interest Rate = Nominal Interest Rate - Inflation Rate
Lower real interest rates encourage borrowing and investment, boosting consumption (C) and investment (I) in the circular flow, whereas higher rates have the opposite effect. Changes in the base rate also influence the exchange rate through 'hot money' flows.
较低的实际利率鼓励借款和投资，提升循环流量中的消费 C 和投资 I，而较高的利率则相反。基准利率的变动还会通过“热钱”流动影响汇率。
The central bank uses interest rate policy to keep inflation close to the target (e.g., 2% in the UK) and support economic growth. The transmission mechanism describes how a rate change feeds through to spending and output.
中央银行运用利率政策将通胀率控制在目标附近（如英国为2%），并支持经济增长。传导机制描述了利率变动如何影响支出和产出。
12. Key Ratios & Additional Quick Checks | 常用比率与快速核查
Besides the main formulas, some ratios and quick checks are useful in data-response questions:
除了主要公式外，一些比率和快速核查方法在数据分析题中非常有用：
Average propensity to consume (APC): APC = Consumption / Disposable Income
平均消费倾向（APC）： APC = 消费 / 可支配收入
Index numbers: Index = (Value in current year / Value in base year) × 100
指数： 指数 = （当年数值 / 基年数值）× 100
Share of income spent: Percentage of income on a good = (Spending on good / Total income) × 100
支出份额： 某种商品支出占收入比重 = （在该商品上的支出 / 总收入）× 100
These can help you interpret inflation indices, time-series data, and patterns of consumption.
这些有助于解读通胀指数、时间序列数据和消费模式。
Always remember to show your workings clearly in calculations and relate your answer to the economic context provided in the exam question.
在计算题中始终清晰地展示运算步骤，并将答案与考题提供的经济背景联系起来。
Published by TutorHao | Economics Revision Series | aleveler.com
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