📚 Year 12 CCEA Economics: Formula & Theorem Quick Reference Handbook | 12年级 CCEA 经济公式定理速查手册
As a Year 12 Economics student following the CCEA specification, having a firm grasp of essential formulas and theorems is crucial for success. This quick reference handbook summarises key equations across microeconomics and macroeconomics, from elasticity calculations to the multiplier effect and beyond.
作为一名学习CCEA课程（12年级）的经济学学生，牢固掌握关键公式与定理对于考试成功至关重要。本速查手册总结了微观经济学和宏观经济学的核心公式，从弹性计算到乘数效应等，帮助你高效复习。
1. Price, Income, Cross & Supply Elasticities | 价格、收入、交叉与供给弹性
asures the responsiveness of quantity demanded to a change in price. The formula is: PED = %ΔQd / % icates elastic demand; less than 1 indicates inelastic demand; equal to 1 is unit elastic.
需求价格弹性（PED）衡量需求量对价格变化的反应程度。公式为：PED = %ΔQd / %ΔP。数值大于1表示富有弹性；小于1表示缺乏弹性；等于1为单位弹性。
icity of demand (YED) calculates the responsiveness of demand to a change in income: YED = %ΔQd / %. A positive YED indicates a normal good, while a negative YED signifies an inferior good.
需求的收入弹性（YED）衡量需求对收入变化的反应程度：YED = %ΔQd / %ΔY。正值为正常品，负值为低档品。
f demand (XED) shows how the demand for good A responds to a price change in good B: XED = %ΔQd of A / %ΔP of B. A positive value means substitutes; a negative value means complements.
需求的交叉价格弹性（XED）表示A商品需求量对B商品价格变化的反应：XED = %ΔQd A / %ΔP B。正值为替代品；负值为互补品。
e elasticity of supply (PES) captures how much quantity supplied changes with price: PES = %ΔQs / %ΔP. A value above 1 is elastic supply; below 1 is inelastic supply.
供给价格弹性（PES）反映供给量随价格变动的程度：PES = %ΔQs / %ΔP。数值大于1为富有弹性；小于1为缺乏弹性。
2. Costs of Production | 生产成本
t (TC) is the sum of total fixed cost (TFC) and total variable cost (TVC): TC = TFC + TVC.
总成本（TC）是总固定成本（TFC）与总可变成本（TVC）之和：TC = TFC + TVC。
Average cost (AC) is total cost per unit of output: AC = TC / Q, where Q is output.
平均成本（AC）是每单位产出的总成本：AC = TC / Q，Q为产量。
erage variable cost (AVC) are given by: AFC = TFC / Q; AVC = TVC / Q. Thus AC = AFC + AVC.
平均固定成本（AFC）和平均可变成本（AVC）计算如下：AFC = TFC / Q；AVC = TVC / Q。因此 AC = AFC + AVC。
arginal cost (MC) is the change in total cost from producing one more unit: MC = ΔTC / ΔQ.
边际成本（MC）是增加一单位产量带来的总成本变化：MC = ΔTC / ΔQ。
3. Revenue and Profit | 收益与利润
Total revenue (TR) equals price multiplied by quantity sold: TR = P × Q.
总收益（TR）等于价格乘以销售量：TR = P × Q。
Average revenue (AR) is revenue per unit sold, which equals the price: AR = TR / Q = P.
平均收益（AR）是每单位销售的收益，等于价格：AR = TR / Q = P。
revenue (MR) is the addition to total revenue from selling one extra unit: MR = ΔTR / ΔQ.
边际收益（MR）是增加销售一单位所带来的总收益变化：MR = ΔTR / ΔQ。
Profit (π) is the difference between total revenue and total cost: Profit = TR – TC. The break-even point occurs when TR = TC, so profit is zero.
利润（π）是总收益与总成本之差：利润 = TR – TC。盈亏平衡点出现在TR = TC时，利润为零。
4. Market Efficiency and Welfare | 市场效率与福利
the market price. For a straight-line demand, CS = ½ × (quantity) × (maximum willing price – market price).
消费者剩余（CS）是需求曲线以下、市场价格以上的面积。对于线性需求，CS = ½ × 数量 × (最大支付意愿 – 市场价格)。
s the area above the supply curve and below the price: PS = ½ × (quantity) × (market price – minimum supply price).
生产者剩余（PS）是供给曲线以上、价格以下的面积：PS = ½ × 数量 × (市场价格 – 最低供给价格)。
loss (DWL) is the loss in total surplus when the market is not at competitive equilibrium—often a triangle with area ½ × (change in quantity) × (price wedge).
社会剩余 = 消费者剩余 + 生产者剩余。无谓损失（DWL）是市场未达到竞争均衡时的总剩余损失，通常为三角形面积：½ × 数量变化 × 价格楔子。
oductive efficiency is achieved when firms produce at the lowest point on the average cost curve.
配置效率发生在价格等于边际成本（P = MC）时。生产效率则要求企业在平均成本曲线的最低点生产。
5. Macroeconomic Performance Indicators | 宏观经济表现指标
l: GDP deflator = (Nominal GDP / Real GDP) × 100. It is a comprehensive inflation measure.
GDP平减指数衡量整体价格水平变化：GDP平减指数 = (名义GDP / 实际GDP) × 100。它是一个综合性的通货膨胀指标。
Inflation rate using the Consumer Price Index (CPI): Inflation rate = [(CPI₂ – CPI₁) / CPI₁] × 100, where CPI₁ is the earlier period.
使用消费者价格指数（CPI）计算通胀率：通胀率 = [(CPI₂ – CPI₁) / CPI₁] × 100，CPI₁为前期指数。
ut actively seeking work: Unemployment rate = (Number of unemployed / Labour force) × 100.
失业率是劳动力中失业但积极寻找工作的人口比例：失业率 = (失业人数 / 劳动力总数) × 100。
population) × 100. It tells us what share of the adult population is economically active.
劳动参与率 = (劳动力 / 劳动年龄人口) × 100。它表明成年人中参与经济活动的比例。
6. Aggregate Demand and the Multiplier | 总需求与乘数
Aggregate demand (AD) is the total spending on domestic output: AD = C + I + G + (X – is consumption, I is investment, G is government spending, X is exports, and M is imports.
总需求（AD）是国内产出的总支出：AD = C + I + G + (X – M)，其中C为消费、I为投资、G为政府支出、X为出口、M为进口。
income: MPC = ΔC / ΔY. The marginal propensity to save (MPS) = ΔS / ΔY, and MPC + MPS = 1.
边际消费倾向（MPC）是收入增加一单位所带来的消费变化：MPC = ΔC / ΔY。边际储蓄倾向（MPS）= ΔS / ΔY，并且MPC + MPS = 1。
In a closed economy with no government, the simple multiplier (k) is: k = 1 / (1 – PC) = 1 / MPS. This shows the magnified effect of an initial injection on national income.
在无政府的封闭经济中，简单乘数（k）为：k = 1 / (1 – MPC) = 1 / MPS。它表示初始注入对国民收入的放大效应。
tiplier becomes: k = 1 / (MPS + MPT + MPM). This is the realistic open-economy multiplier.
考虑到税收（MPT）和进口（MPM）等漏出时，乘数变为：k = 1 / (MPS + MPT + MPM)，即现实中的开放经济乘数。
7. Equilibrium National Income | 均衡国民收入
tional income occurs where aggregate demand equals national output (Y): Y = C + I + G + (X – M). Alternatively, injections (I + G + X) equal withdrawals (S + T + M).
均衡国民收入发生在总需求等于国民产出（Y）时：Y = C + I + G + (X – M)。也可表达为注入（I + G + X）等于漏出（S + T + M）。
The output gap is the difference between actual GDP and potential (full-employment) GDP. A negative output gap indicates spare capacity; a positive gap suggests an overheating economy.
产出缺口是实际GDP与潜在（充分就业）GDP之差。负缺口表示产能过剩；正缺口暗示经济过热。
8. Money and the Credit Multiplier | 货币与信用乘数
ement ratio (r): Money multiplier = 1 / r. For example, with r = 0.2, the multiplier is 5.
信用（货币）乘数表示基于准备金率（r），货币供应从初始存款的扩张倍数：货币乘数 = 1 / r。例如，r = 0.2时，乘数为5。
Money multiplier. This process continues until there are no more excess reserves to lend.
创造的货币供应总量 = 初始超额准备金 × 货币乘数。这一过程持续到没有超额准备金可贷出为止。
9. International Trade and Exchange Rates | 国际贸易与汇率
An increase indicates that the country can buy more imports for a given volume of exports.
贸易条件衡量出口相对于进口的价格：贸易条件 = (出口价格指数 / 进口价格指数) × 100。数值上升表示同等数量的出口能换回更多的进口。
, where P* is the foreign price level and P is the domestic price level. An increase implies a real appreciation.
实际汇率（RER）用价格水平差异调整名义汇率（e）：RER = e × (P* / P)，P*为外国价格水平，P为本国价格水平。上升表示实际升值。
ccount balance = 0. In practice, net errors and omissions ensure the accounts sum to zero.
国际收支恒等式：经常账户余额 + 资本账户余额 + 金融账户余额 = 0。实务中，净误差与遗漏确保各账户总和归零。
10. Economic Growth and Productivity | 经济增长与生产率
rowth rate measures the percentage change in real GDP over time: Growth rate = [(Real GDPₜ – Real GDPₜ₋₁) / Real GDPₜ₋₁] × 100%. Sustained growth raises living standards.
实际经济增长率衡量实际GDP随时间的变化百分比：增长率 = [(当期实际GDP – 前期实际GDP) / 前期实际GDP] × 100%。持续增长提高生活水平。
ome per person: GDP per capita = Real GDP / Population. It is a key development indicator.
人均GDP表示人均平均收入：人均GDP = 实际GDP / 人口。它是一个关键的发展指标。
ur input (hours or workers). Productivity growth is vital for long-run economic expansion.
劳动生产率衡量每
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