📚 SQA Economics Formula & Theorem Quick Reference Handbook | SQA 经济公式定理速查手册
This handbook compiles the essential formulas, theorems and quantitative relationships required for the SQA Advanced Higher Economics course. It is designed as a rapid revision tool to help you recall definitions, calculate elasticities, interpret cost structures and analyse macroeconomic policy. Each entry is presented with the formula in standard notation, followed by a short explanation of its use and significance. Whether you are preparing for an end‑of‑topic test or the final examination, keep this guide close to hand.
本手册汇编了 SQA 高级高等经济课程所需的关键公式、定理和数量关系，旨在作为快速复习工具，帮助你回忆定义、计算弹性、理解成本结构并分析宏观经济政策。每条内容以标准符号列出公式，随后简要说明其用途和意义。无论你在准备单元测验还是最终考试，都可将本指南放在手边。
1. 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 the good’s own price. It is always negative (or zero), but by convention we often ignore the minus sign.
需求价格弹性衡量需求量对商品自身价格变化的反应程度。它始终为负（或零），但习惯上我们常忽略负号。
PED = (% Change in Quantity Demanded) ÷ (% Change in Price)
or|或
PED = (ΔQd / Qd) ÷ (ΔP / P)
If |PED| > 1, demand is elastic; luxury goods often fall here. If |PED| < 1, demand is inelastic, typically for necessities. If |PED| = 1, demand is unit elastic. Knowledge of PED helps firms predict revenue changes when altering price.
若 |PED| > 1，需求富有弹性，奢侈品往往如此；若 |PED| < 1，需求缺乏弹性，多为必需品；若 |PED| = 1，需求为单位弹性。掌握 PED 有助于企业预测价格变动对总收益的影响。
For a linear demand curve, PED varies along the curve: it is elastic above the midpoint and inelastic below. The total revenue test links PED to revenue: if demand is elastic, a price cut raises total revenue; if inelastic, a price cut lowers total revenue.
在线性需求曲线上，PED 沿曲线变化：中点以上富有弹性，中点以下缺乏弹性。总收益检验将 PED 与收益联系起来：需求富有弹性时，降价增加总收益；缺乏弹性时，降价减少总收益。
2. Price Elasticity of Supply (PES) | 供给价格弹性
Price elasticity of supply indicates how responsive quantity supplied is to a change in price. Unlike PED, it is normally positive because higher prices incentivise greater output.
供给价格弹性表明供给量对价格变化的反应程度。与 PED 不同，PES 通常为正，因为高价激励更多产出。
PES = (% Change in Quantity Supplied) ÷ (% Change in Price)
or|或
PES = (ΔQs / Qs) ÷ (ΔP / P)
Values above 1 indicate elastic supply (firms can easily expand output), values below 1 indicate inelastic supply (often due to capacity constraints or time lags). In the momentary period, supply is almost perfectly inelastic; in the long run, it tends to be more elastic as all factors become variable.
数值大于 1 表示供给富有弹性（企业可轻松扩大产量），小于 1 表示供给缺乏弹性（常因产能限制或时滞）。在瞬间期，供给几乎完全无弹性；长期中，所有要素可变，供给弹性通常更大。
3. Cross Elasticity of Demand (XED) and Income Elasticity of Demand (YED) | 需求交叉弹性与收入弹性
Cross elasticity of demand measures how the quantity demanded of one good responds to a price change of another good. Income elasticity measures the response of demand to a change in consumer incomes.
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。收入弹性衡量需求对消费者收入变动的反应。
XED = (% ΔQd of Good A) ÷ (% ΔPrice of Good B)
Positive XED → substitutes; negative XED → complements; zero → independents. Strong positive values indicate close substitutes; strongly negative values indicate strong complements.
正的 XED → 替代品；负的 XED → 互补品；零 → 独立品。数值越大越正，替代性越强；数值越小越负，互补性越强。
YED = (% ΔQd) ÷ (% ΔIncome)
Normal goods have positive YED (luxuries > 1, necessities 0‑1). Inferior goods have negative YED. These elasticities help businesses forecast demand shifts during economic cycles and plan product portfolios.
正常品具有正的 YED（奢侈品 > 1，必需品 0‑1）。劣等品的 YED 为负。这些弹性有助于企业预测经济周期中的需求变化并规划产品组合。
4. Cost Structures: Total, Average and Marginal Cost | 成本结构：总成本、平均成本与边际成本
A firm’s cost curves are central to the theory of supply. Understanding how costs behave in the short run and long run underpins pricing and output decisions.
企业的成本曲线是供给理论的核心。理解成本在短期和长期中的行为是定价与产量决策的基础。
TC = TFC + TVC
Total cost (TC) is the sum of total fixed cost (TFC) and total variable cost (TVC). Fixed costs do not vary with output (e.g. rent), while variable costs rise with output (e.g. raw materials, labour).
总成本 (TC) 是总固定成本 (TFC) 与总可变成本 (TVC) 之和。固定成本不随产量变化（如租金），可变成本随产量增加而上升（如原材料、劳动力）。
AFC = TFC ÷ Q
AVC = TVC ÷ Q
ATC (or AC) = TC ÷ Q = AFC + AVC
Average fixed cost falls continuously as output increases (spreading overheads). Average variable cost typically falls initially due to increasing returns, then rises due to diminishing marginal returns. Average total cost (ATC) therefore has a U‑shape.
平均固定成本随产量增加而持续下降（分摊间接费用）。平均可变成本通常因报酬递增先降后升，呈 U 型；平均总成本 (ATC) 也呈 U 型。
MC = ΔTC ÷ ΔQ = ΔTVC ÷ ΔQ
Marginal cost is the extra cost of producing one more unit. The MC curve cuts the AVC and ATC curves at their minimum points. This relationship is essential for deriving the firm’s supply curve in perfect competition.
边际成本是增加一单位产量带来的总成本增量。MC 曲线穿过 AVC 和 ATC 曲线的最低点。这一关系对推导完全竞争下企业的供给曲线至关重要。
5. Revenue, Profit Maximisation and Shutdown Condition | 收益、利润最大化与停业条件
Revenue concepts are straightforward but form the core of profit analysis. Profit is maximised where marginal revenue equals marginal cost, provided the firm covers its variable costs in the short run.
收益概念简单，却是利润分析的核心。利润在边际收益等于边际成本处实现最大化，前提是企业在短期内至少能覆盖可变成本。
TR = P × Q
AR = TR ÷ Q = P
MR = ΔTR ÷ ΔQ
Under perfect competition, AR = MR = price, so the demand curve facing the firm is horizontal. For a monopolist, MR lies below AR because the firm must lower price to sell extra units.
在完全竞争下，AR = MR = 价格，企业面临水平的需求曲线。对垄断者而言，MR 低于 AR，因为要多卖就必须降价。
The profit‑maximising rule: produce where MC = MR. In the short run, a firm should shut down if P < AVC; in the long run, it exits if P < ATC. Normal profit occurs when TR = TC (AR = ATC); supernormal profit when TR > TC.
利润最大化规则：在 MC = MR 处生产。短期中，若 P < AVC，企业应停业；长期中，若 P < ATC，企业退出。当 TR = TC（AR = ATC）时获得正常利润；TR > TC 时获得超额利润。
6. Market Concentration Ratios and the Herfindahl–Hirschman Index | 市场集中度比率与赫芬达尔‑赫希曼指数
Market structure is often judged by concentration measures. The n‑firm concentration ratio and the Herfindahl–Hirschman Index (HHI) are the two most common tools used in competition policy.
市场结构常通过集中度指标判断。n 公司集中度比率和赫芬达尔‑赫希曼指数（HHI）是竞争政策中最常用的两种工具。
CRn = (Combined market share of the largest n firms) ÷ (Total market size) × 100
For example, a five‑firm concentration ratio CR₅ of 80% indicates a highly concentrated market. A ratio above 60% typically signals an oligopoly; above 80% a tight oligopoly or monopoly.
例如，五公司集中度比率 CR₅ 为 80% 表明市场高度集中。比率高于 60% 通常标志着寡头垄断；高于 80% 为紧密寡头或垄断。
HHI = Σ (market share of each firm)²
Market shares are expressed as whole numbers (e.g. 25% → 25, not 0.25). The HHI ranges from near zero (perfect competition) to 10,000 (pure monopoly). In the UK, an HHI above 1,000 is considered concentrated; above 2,000 suggests a merger may be challenged.
市场份额以整数表示（如 25% → 25）。HHI 范围从近乎零（完全竞争）到 10,000（纯垄断）。在英国，HHI 超过 1,000 视为集中；超过 2,000 意味着合并可能受到审查。
7. Macroeconomic Indicators: GDP, Inflation and Unemployment | 宏观经济指标：GDP、通胀与失业
Understanding how key macro variables are calculated is vital for policy evaluation. This section provides the standard formulae for GDP (expenditure approach), the GDP deflator, CPI inflation and the unemployment rate.
理解关键宏观变量如何计算对政策评估至关重要。本节给出 GDP（支出法）、GDP 平减指数、CPI 通胀率及失业率的标准公式。
GDP = C + I + G + (X – M)
Where C = consumption, I = investment, G = government spending, X = exports, M = imports. This is the expenditure measure of GDP at market prices. To move from nominal to real GDP, we use a price index.
其中 C = 消费，I = 投资，G = 政府支出，X = 出口，M = 进口。这是按市场价格计算的 GDP 支出指标。从名义 GDP 到实际 GDP 需使用价格指数。
Real GDP = (Nominal GDP ÷ GDP Deflator) × 100
GDP Deflator = (Nominal GDP ÷ Real GDP) × 100
The CPI (Consumer Price Index) measures the average change in prices paid by households. Inflation rate is the annual percentage change in CPI.
消费者价格指数 (CPI) 衡量家庭支付价格的平均变动。通胀率为 CPI 年百分比变化。
Inflation Rate = [(CPIt – CPIt‑1) ÷ CPIt‑1] × 100
The unemployment rate is calculated from the Labour Force Survey and follows the ILO definition.
失业率根据劳动力调查按国际劳工组织定义计算。
Unemployment Rate = (Number of Unemployed ÷ Labour Force) × 100
The labour force comprises the employed plus the unemployed who are actively seeking work.
劳动力包括就业者加上正在积极寻找工作的失业者。
8. The Multiplier Effect and Marginal Propensities | 乘数效应与边际倾向
The multiplier is a cornerstone of Keynesian economics, explaining how an initial injection of spending leads to a larger final increase in aggregate demand and national income.
乘数是凯恩斯经济学的基石，解释了初始支出注入如何带来总需求和国民收入更大幅度的最终增长。
Multiplier (k) = 1 ÷ (1 – MPC) = 1 ÷ MPS + MPT + MPM
where MPC = marginal propensity to consume, MPS = marginal propensity to save, MPT = marginal propensity to tax, MPM = marginal propensity to import. The simple closed‑economy multiplier (no government or trade) is k = 1/(1 – MPC). In an open economy with government, the denominator expands to include all leakages.
其中 MPC = 边际消费倾向，MPS = 边际储蓄倾向，MPT = 边际税收倾向，MPM = 边际进口倾向。简单封闭经济乘数（无政府与贸易）为 k = 1/(1 – MPC)。在开放经济有政府时，分母扩展为包括所有漏出。
MPC + MPS = 1 (simplest case)
The larger the MPC, the larger the multiplier. Conversely, a high marginal propensity to withdraw dampens the multiplier effect. Policymakers use the multiplier to estimate the impact of fiscal stimulus.
MPC 越大，乘数越大。相反，高边际漏出倾向会减弱乘数效应。政策制定者利用乘数估算财政刺激的影响。
9. Comparative Advantage and the Terms of Trade | 比较优势与贸易条件
Comparative advantage is the principle that mutually beneficial trade is possible even when one country is absolutely more efficient in producing all goods. It is driven by differences in opportunity cost.
比较优势是指即使一国在所有商品生产上都绝对更高效，双方仍可从贸易中获益的原则。它源于机会成本的差异。
Opportunity Cost of Good X = (Units of Good Y sacrificed) ÷ (Units of Good X gained)
A country should specialise in the good for which its opportunity cost is lower, and trade for the other. The terms of trade reflect the rate at which goods are exchanged internationally.
一国应专业化生产其机会成本较低的商品，并用它交换其他商品。贸易条件反映国际间商品交换的比率。
Terms of Trade (TOT) = (Index of Export Prices ÷ Index of Import Prices) × 100
An improvement in the TOT (higher index) means a country can buy more imports for a given volume of exports. A deterioration has the opposite effect. TOT changes affect the current account and real national income.
贸易条件改善（指数上升）意味着一国以一定量出口可购买更多进口；恶化则相反。贸易条件变化影响经常账户和实际国民收入。
10. Exchange Rates: Real and Nominal | 汇率：名义与实际
Exchange rates determine the price of one currency in terms of another. In examinations, you need to distinguish between nominal and real exchange rates and understand how they are calculated.
汇率决定了一种货币用另一种货币表示的价格。考试中需要区分名义汇率与实际汇率，并理解计算方法。
Nominal exchange rate: e.g. £1 = $1.25
Real Exchange Rate = (Nominal Rate × Domestic Price Level) ÷ Foreign Price Level
A real appreciation occurs when the real exchange rate rises, making domestic goods relatively more expensive. The effective exchange rate is a weighted average against a basket of trading partners’ currencies, often expressed as an index.
实际升值出现在实际汇率上升时，使得本国商品相对更贵。有效汇率是对一篮子贸易伙伴货币的加权平均值，常以指数表示。
In a floating system, exchange rates are determined by supply and demand for currencies. In a fixed system, the central bank intervenes to maintain a target rate. Managed floats combine the two.
在浮动汇率制下，汇率由货币供求决定。固定汇率制下，央行干预以维持目标汇率。管理浮动则结合两者。
11. The Quantity Theory of Money | 货币数量论
The quantity theory of money provides a long‑run link between the money supply and the price level. It is often associated with monetarism and the work of Milton Friedman.
货币数量论提供了货币供给与物价水平之间的长期联系，常与货币主义及弗里德曼的著作联系在一起。
MV = PQ
Where M = money supply, V = velocity of circulation (assumed stable in the long run), P = general price level, Q = real output (or real GDP). In growth rate form: ΔM + ΔV ≈ ΔP + ΔQ. Monetarists argue that inflation is primarily a monetary phenomenon: if the money supply grows faster than real output, the price level will rise.
其中 M = 货币供给，V = 货币流通速度（长期假定稳定），P = 一般物价水平，Q = 实际产出（或实际 GDP）。以增长率形式表达：ΔM + ΔV ≈ ΔP + ΔQ。货币主义者认为通胀主要是货币现象：若货币供给增长快于实际产出，物价水平将上升。
Velocity is defined as V = (Nominal GDP) ÷ M. While the simple form suggests a direct proportionality, modern refinements consider that V may vary in the short run due to financial innovation or changes in confidence.
流通速度定义为 V = 名义 GDP ÷ M。虽然简单形式表明直接比例关系，现代修正认为 V 在短期内可能因金融创新或信心变化而波动。
12. The Phillips Curve and the Output Gap | 菲利普斯曲线与产出缺口
The Phillips Curve illustrates a short‑run trade‑off between inflation and unemployment. The concept is important for evaluating demand‑side policies and supply‑side improvements.
菲利普斯曲线描述了短期中通胀与失业之间的权衡取舍。这一概念对评估需求侧政策和供给侧改善十分重要。
The original curve: lower unemployment → higher wage inflation → higher price inflation. The expectations‑augmented Phillips Curve shows that in the long run the curve is vertical at the natural rate of unemployment (NAIRU), meaning no long‑run trade‑off exists.
原始曲线：较低的失业 → 较高的工资通胀 → 较高的物价通胀。附加预期的菲利普斯曲线显示长期中曲线在自然失业率 (NAIRU) 处垂直，即不存在长期权衡。
Output Gap = (Actual GDP – Potential GDP) ÷ Potential GDP × 100
A positive output gap (actual > potential) puts upward pressure on inflation; a negative gap (recessionary gap) creates downward pressure. This relationship is captured by the short‑run Phillips Curve and helps central banks set interest rates using the Taylor Rule or similar frameworks.
正产出缺口（实际 > 潜在）给通胀带来上行压力；负缺口（衰退缺口）则带来下行压力。这种关系通过短期菲利普斯曲线体现，帮助中央银行借助泰勒规则或类似框架设定利率。
Published by TutorHao | Economics Revision Series | aleveler.com
更多咨询请联系16621398022（同微信）
屏轩国际教育cambridge primary/secondary checkpoint, cat4, ukiset,ukcat,igcse,alevel,PAT,STEP,MAT, ibdp,ap,ssat,sat,sat2课程辅导，国外大学本科硕士研究生博士课程论文辅导Cancel reply