📚 Year 11 AQA Economics Formula & Theorem Quick Reference Handbook | AQA Year 11 经济公式定理速查手册
This handbook provides a concise summary of the essential formulas and theorems you need for the AQA GCSE Economics (Year 11) exam. Mastering these quantitative tools is crucial for analysing markets, understanding macroeconomic performance and answering data-response questions accurately.
本手册简要总结了 AQA GCSE 经济学（Year 11）考试所需的核心公式和定理。掌握这些量化工具对于分析市场、理解宏观经济表现以及准确回答数据分析题至关重要。
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 price. It is calculated using the formula:
需求价格弹性衡量需求量对价格变动的反应程度。其计算公式为：
PED = (%ΔQd) ÷ (%ΔP)
tic. If PED = 1, demand is unit elastic. And if PED = ∞, demand is perfectly elastic; if PED = 0, demand is perfectly inelastic.
若 PED > 1，需求富有价格弹性，价格变动导致需求量更大幅度变动。PED < 1 时，需求缺乏价格弹性。PED = 1 为单位弹性。PED = ∞ 时为完全弹性，PED = 0 时为完全无弹性。
| PED value | Elasticity type | Effect on total revenue (P↑) |
| PED > 1 | Elastic | Revenue falls |
| PED < 1 | Inelastic | Revenue rises |
| PED = 1 | Unit elastic | Revenue unchanged |
The table above shows the relationship between PED and total revenue when price increases. Knowing PED helps firms set prices to maximise sales revenue.
上表显示了价格上升时 PED 与总收入的关系。了解 PED 有助于企业制定价格以最大化销售收入。
2. Price Elasticity of Supply (PES) | 供给价格弹性
Price elasticity of supply measures how much the quantity supplied changes when the price changes. The formula is:
供给价格弹性衡量价格变化时供给量的变动程度。其公式为：
PES = (%ΔQs) ÷ (%ΔP)
an 1 indicates inelastic supply, often due to limited spare capacity or long production times. PES = 0 means perfectly inelastic supply, and PES = ∞ means perfectly elastic supply.
PES 值大于 1 表示供给弹性充足，生产者可以迅速增加产量而成本上升不大。PES 小于 1 表示供给缺乏弹性，通常由于闲置产能有限或生产周期长。PES = 0 为完全无弹性供给，PES = ∞ 为完全弹性供给。
3. Income Elasticity of Demand (YED) | 需求收入弹性
Income elasticity of demand measures the responsiveness of demand to changes in consumer income. The formula is:
需求收入弹性衡量需求对消费者收入变动的反应程度。其公式为：
YED = (%ΔQd) ÷ (%ΔIncome)
If YED is positive, the good is a normal good; if YED is negative, it is an inferior good. For normal goods, a YED greater than 1 indicates a luxury good, while a YED between 0 and 1 indicates a necessity. Firms use YED to forecast how demand will shift as the economy grows or shrinks.
若 YED 为正，该商品为正常品；若为负，则为低档品。对于正常品，YED 大于 1 表示奢侈品，0 至 1 之间表示必需品。企业利用 YED 预测经济增长或衰退时需求的变化。
4. Cross Elasticity of Demand (XED) | 需求交叉弹性
Cross elasticity of demand measures the responsiveness of demand for one good to a change in the price of another good. The formula is:
需求交叉弹性衡量一种商品的需求对另一种商品价格变动的反应程度。其公式为：
XED = (%ΔQd of good A) ÷ (%ΔP of good B)
A positive XED indicates substitute goods (e.g., tea and coffee). A negative XED indicates complementary goods (e.g., printers and ink cartridges). An XED close to zero suggests the goods are unrelated. Cross elasticity helps businesses understand competitors' pricing impact and plan marketing strategies.
XED 为正表示替代品（如茶和咖啡）。XED 为负表示互补品（如打印机和墨盒）。XED 接近于零表示商品不相关。交叉弹性帮助企业理解竞争对手定价的影响并制定营销策略。
5. Basic Cost Concepts | 基本成本概念
Firms face various types of costs in the short run. Total cost (TC) is the sum of total fixed costs (TFC) and total variable costs (TVC). The formula is:
企业在短期面临各种成本。总成本（TC）是总固定成本（TFC）与总可变成本（TVC）之和。其公式为：
TC = TFC + TVC
÷ Q, and average variable cost (AVC) is TVC ÷ Q. Therefore, ATC = AFC + AVC.
平均总成本（ATC 或 AC）等于总成本除以产量（Q）。平均固定成本（AFC）= TFC ÷ Q，平均可变成本（AVC）= TVC ÷ Q。因此，ATC = AFC + AVC。
change in total cost divided by the change in quantity: MC = ΔTC ÷ ΔQ.
边际成本（MC）是额外生产一单位产量所增加的成本。其计算公式为总成本变动除以产量变动：MC = ΔTC ÷ ΔQ。
6. Revenue and Profit Formulas | 收益与利润公式
Total revenue (TR) is the income a firm receives from selling its products. It is found by multiplying price (P) by quantity sold (Q):
总收入（TR）是企业销售产品所获得的收入，等于价格（P）乘以销量（Q）：
TR = P × Q
which equals the price when all units are sold at the same price: AR = TR ÷ Q = P.
平均收入（AR）是每单位销售所得收入，当所有商品同价出售时，AR = TR ÷ Q = P。
Profit is the difference between total revenue and total costs. The accounting profit formula is:
利润是总收入与总成本之间的差额。会计利润公式为：
Profit = TR - TC
ormal profit occurs when TR > TC, and a loss occurs when TR < TC. Understanding profit maximisation is central to the theory of the firm.
当 TR = TC 时企业盈亏平衡。TR > TC 时获得超额利润，TR < TC 时出现亏损。理解利润最大化是企业理论的核心。
7. Total, Average and Marginal Relationships | 总、平均与边际关系
In economics, the relationship between totals, averages and marginals helps to analyse production and costs. For any variable, if the marginal value is above the average, the average rises; if the marginal is below the average, the average falls.
在经济学中，总量、平均量与边际量的关系有助于分析生产和成本。对于任何变量，若边际量高于平均量，平均量上升；若边际量低于平均量，平均量下降。
For example, when marginal cost (MC) is less than average total cost (ATC), ATC is falling. When MC > ATC, ATC is rising. The MC curve always intersects the ATC curve at its minimum point. This marginal-average rule applies to product curves as well: when marginal product (MP) > average product (AP), AP increases.
例如，当边际成本（MC）低于平均总成本（ATC）时，ATC 下降。当 MC > ATC 时，ATC 上升。MC 曲线总是在 ATC 曲线的最低点与其相交。这一边际-平均法则同样适用于产量曲线：当边际产量（MP）> 平均产量（AP）时，AP 递增。
8. Aggregate Demand Components | 总需求构成
Aggregate demand (AD) is the total spending on goods and services produced in an economy over a period of time. It is calculated as:
总需求（AD）是在一段时期内，经济中用于所生产商品和服务的总支出。其计算公式为：
AD = C + I + G + (X - M)
C represents consumption spending by households, I is investment spending by firms, G is government spending, X is exports and M is imports. Net exports (X - M) is the difference between the value of exports and imports. A rise in any component, ceteris paribus, will increase AD and shift the AD curve to the right.
C 表示家庭消费支出，I 为企业投资支出，G 为政府支出，X 为出口，M 为进口。净出口（X - M）是出口值与进口值之差。其他条件不变，任何一个组成部分的增加都会提高总需求，使 AD 曲线右移。
9. The Multiplier and Marginal Propensities | 乘数与边际倾向
nsities. The marginal propensity to consume (MPC) is the proportion of additional income spent on consumption. The marginal propensity to save (MPS) is the proportion saved. MPC + MPS = 1.
乘数效应解释了一笔初始支出变动如何导致国民收入更大的最终变动。其基础在于边际倾向。边际消费倾向（MPC）是新增收入中用于消费的比例。边际储蓄倾向（MPS）是储蓄的比例。MPC + MPS = 1。
For a closed economy with no government, the simple multiplier (k) is:
在一个没有政府的封闭经济中，简单乘数（k）为：
k = 1 ÷ (1 - MPC) = 1 ÷ MPS
C is 0.8, the multiplier is 1 ÷ 0.2 = 5. Thus, an initial increase in investment of £1 million could eventually raise national income by £5 million. The multiplier concept helps policymakers gauge the impact of fiscal stimulus.
如果 MPC 为 0.8，乘数为 1 ÷ 0.2 = 5。因此，初始增加 100 万英镑的投资最终可使国民收入增加 500 万英镑。乘数概念有助于决策者衡量财政刺激的效果。
10. Measuring the Economy: Inflation, Unemployment and Growth | 衡量经济：通货膨胀、失业与增长
Inflation is the sustained rise in the general price level. The most common measure is the Consumer Prices Index (CPI). The inflation rate can be calculated using:
通货膨胀是物价总水平的持续上升。最常用的衡量指标是消费者价格指数（CPI）。通货膨胀率可用下式计算：
= [(CPI in current year - CPI in previous year) ÷ CPI in previous year] × 100
Unemployment rate is the percentage of the labour force that is willing and able to work but cannot find a job. It is calculated as:
失业率是劳动力中愿意且有能力工作但找不到工作的人所占的百分比。其计算公式为：
Unemployment rate = (Number of unemployed ÷ Labour force) × 100
Economic growth is measured by the percentage change in real Gross Domestic Product (GDP). Real GDP strips out the effect of inflation:
经济增长通过实际国内生产总值（GDP）的百分比变动来衡量。实际 GDP 剔除了通货膨胀的影响：
eal GDP current year - Real GDP previous year) ÷ Real GDP previous year × 100
These indicators form the basis of a government's macroeconomic objectives. In AQA GCSE questions, you may be asked to calculate or interpret these rates from data tables and graphs.
这些指标构成政府宏观经济目标的基础。在 AQA GCSE 考题中，可能要求你根据数据表和图表计算或解读这些比率。
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