📚 Year 10 AQA Economics: Formula & Theorem Quick Guide | AQA 经济学公式定理速查指南
In Year 10 AQA Economics, mastering key formulas, theorems, and relationships is essential for understanding how markets and economies work. This quick-reference handbook brings together every important equation and principle from the GCSE specification, with clear explanations in both English and Mandarin. Use it to revise for tests, complete homework, and build a solid foundation for Year 11.
在 Year 10 的 AQA 经济学课程中，掌握关键的公式、定理和关系对于理解市场与经济的运行至关重要。这本速查手册汇集了 GCSE 大纲中的所有重要方程和原理，并提供清晰的中英双语解释。你可以用它来复习备考、完成作业，并为 Year 11 的学习打下坚实的基础。
1. Basic Concepts & Production Possibility Frontier | 基本概念与生产可能性边界
Scarcity means that resources are limited while human wants are infinite. This fundamental economic problem forces choices, and every choice involves an opportunity cost – the value of the next best alternative forgone.
稀缺性意味着资源是有限的，而人类的欲望是无限的。这一基本经济问题迫使人们做出选择，而每一个选择都涉及机会成本——即所放弃的次优选择的价值。
The Production Possibility Frontier (PPF) shows the maximum combinations of two goods an economy can produce with its existing resources and technology. The slope of the PPF reflects the opportunity cost of switching production.
生产可能性边界 (PPF) 展示了一个经济体在现有资源和技术条件下所能生产的两种商品的最大组合。PPF 的斜率反映了转换生产的机会成本。
Opportunity cost = Units of Good Y given up ÷ Units of Good X gained
机会成本 = 放弃的商品 Y 数量 ÷ 获得的商品 X 数量
Points inside the PPF are inefficient, points on the curve are efficient, and points outside are unattainable with current resources. Economic growth can shift the PPF outwards.
位于 PPF 内部的点表示无效率，曲线上的点是有效率的，而曲线之外的点在现有资源下无法实现。经济增长会使 PPF 向外移动。
2. Demand and Supply | 需求与供给
The law of demand states that, ceteris paribus (all other things being equal), as the price of a good rises, the quantity demanded falls. The law of supply states that as price rises, the quantity supplied rises.
需求定律指出，在其他条件不变的情况下，商品价格上升时，需求量下降。供给定律指出，价格上升时，供给量上升。
Market equilibrium occurs where quantity demanded equals quantity supplied. The equilibrium price and quantity can be expressed as:
市场均衡发生在需求量等于供给量之时。均衡价格和均衡数量可表示为：
Qd = Qs → (P*, Q*)
Qd = Qs → (P*, Q*)
A shift in the demand or supply curve changes equilibrium, whereas a movement along the curve is caused by a change in price only.
需求曲线或供给曲线的移动会改变均衡，而沿着曲线的移动仅由价格变动引起。
3. Price Elasticity of Demand (PED) | 需求价格弹性 (PED)
PED measures how responsive quantity demanded is to a change in price. Businesses use PED to set prices and predict revenue changes.
需求价格弹性衡量需求量对价格变化的反应程度。企业利用 PED 制定价格并预测收入变化。
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)
emand is unit elastic. The value is taken as an absolute number (ignoring the minus sign).
如果 PED > 1，需求富有弹性；PED < 1，需求缺乏弹性；PED = 1，需求为单位弹性。该数值取绝对值（忽略负号）。
Revenue implications: When demand is elastic, a price rise lowers total revenue; when demand is inelastic, a price rise increases total revenue.
对收入的影响：当需求富有弹性时，提价会减少总收入；当需求缺乏弹性时，提价会增加总收入。
4. Income Elasticity of Demand (YED) | 需求收入弹性 (YED)
YED shows the responsiveness of demand to changes in real income. It helps classify goods as normal or inferior.
需求收入弹性表示需求对实际收入变化的反应程度，用于区分正常商品和劣质商品。
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)
A positive YED indicates a normal good. If YED > 1, it is a luxury good; if 0 < YED < 1, it is a necessity. A negative YED indicates an inferior good.
正的 YED 表示正常商品。若 YED > 1，为奢侈品；若 0 < YED < 1，为必需品。负的 YED 表示劣质商品。
5. Cross Elasticity of Demand (XED) | 需求交叉弹性 (XED)
XED measures how the quantity demanded of one good changes when the price of another good changes. It identifies substitutes and complements.
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化的反应程度，用以识别替代品和互补品。
XED = (% Change in Qd of Good A) ÷ (% Change in Price of Good B)
需求交叉弹性 = (A 商品需求量变化百分比) ÷ (B 商品价格变化百分比)
If XED > 0, the two goods are substitutes. If XED < 0, they are complements. A value close to zero suggests the goods are unrelated.
若 XED > 0，两种商品互为替代品；若 XED < 0，二者为互补品；若接近零，则商品不相关。
6. Price Elasticity of Supply (PES) | 供给价格弹性 (PES)
PES measures the responsiveness of quantity supplied to a change in price. It depends on factors like production time, availability of resources, and spare capacity.
供给价格弹性衡量供给量对价格变化的反应程度，其影响因素包括生产周期、资源可得性以及剩余产能等。
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)
tic; if PES = 1, supply is unit elastic. In the long run, supply tends to be more elastic.
若 PES > 1，供给富有弹性；PES < 1，供给缺乏弹性；PES = 1，供给为单位弹性。长期中，供给通常更具弹性。
7. Costs of Production | 生产成本
Firms face total fixed costs (TFC) that do not vary with output and total variable costs (TVC) that change as output changes. Total cost (TC) is the sum of the two.
企业面临不随产量变化的固定总成本 (TFC) 和随产量变化的可变总成本 (TVC)。总成本 (TC) 是两者之和。
TC = TFC + TVC
总成本 = 总固定成本 + 总可变成本
Average costs are calculated per unit of output:
平均成本按每单位产量计算：
ATC = TC ÷ Q, AFC = TFC ÷ Q, AVC = TVC ÷ Q
平均总成本 = 总成本 ÷ 产量, 平均固定成本 = 总固定成本 ÷ 产量, 平均可变成本 = 总可变成本 ÷ 产量
Marginal cost (MC) is the extra cost of producing one more unit. It is derived from the change in total cost:
边际成本 (MC) 是多生产一单位产品所带来的额外成本，由总成本的变动得出：
MC = ΔTC ÷ ΔQ
边际成本 = 总成本变动 ÷ 产量变动
Economies of scale occur when long-run average costs fall as output increases; diseconomies of scale occur when they rise.
规模经济出现在长期平均成本随产量增加而下降时；规模不经济则出现在其上升时。
8. Revenues and Profit Maximisation | 收益与利润最大化
Total revenue (TR) is the money a firm receives from selling its output. Average revenue (AR) is revenue per unit, which equals the price if all units sell at the same price.
总收入 (TR) 是企业销售产品所获得的收入。平均收入 (AR) 是每单位产品的收入，如果所有产品以相同价格出售，则等于价格。
TR = P × Q, AR = TR ÷ Q = P
总收入 = 价格 × 产量, 平均收入 = 总收入 ÷ 产量 = 价格
Marginal revenue (MR) is the additional revenue from selling one more unit:
边际收入 (MR) 是多卖一单位产品带来的额外收入：
MR = ΔTR ÷ ΔQ
边际收入 = 总收入变动 ÷ 产量变动
Profit is the difference between total revenue and total cost. The profit-maximising condition for any firm is where marginal revenue equals marginal cost.
利润是总收入与总成本之差。任何企业的利润最大化条件是边际收入等于边际成本。
Profit = TR − TC, Maximised when MR = MC
利润 = 总收入 − 总成本, 当 MR = MC 时利润最大
Firms should shut down in the short run if price falls below average variable cost (P < AVC), as they cannot cover variable costs.
在短期中，如果价格低于平均可变成本 (P < AVC)，企业应停产，因为无法弥补可变成本。
9. Macroeconomic Indicators | 宏观经济指标
Gross Domestic Product (GDP) measures the value of all finished goods and services produced within a country in a given period. It can be calculated via the expenditure approach:
国内生产总值 (GDP) 衡量一国在特定时期内生产的所有最终产品和服务的价值，可通过支出法计算：
GDP = C + I + G + (X − M)
GDP = 消费 + 投资 + 政府支出 + (出口 − 进口)
The inflation rate measures the annual percentage increase in the general price level, commonly using the Consumer Price Index (CPI):
通货膨胀率衡量一般物价水平的年增长率，常用消费者价格指数 (CPI) 计算：
Inflation rate = [(CPIcurrent − CPIprevious) ÷ CPIprevious] × 100
通胀率 = [(本年 CPI − 上年 CPI) ÷ 上年 CPI] × 100
The unemployment rate shows the proportion of the labour force that is actively seeking work but cannot find a job:
失业率表示劳动力中积极寻找工作却找不到工作的人口比例：
Unemployment rate = (Number of unemployed ÷ Labour force) × 100
失业率 = (失业人数 ÷ 劳动力总数) × 100
Economic growth is the percentage change in real GDP from one period to another.
经济增长是指实际 GDP 从一个时期到另一个时期的百分比变化。
10. Aggregate Demand and Government Policy | 总需求与政府政策
Aggregate demand (AD) is the total spending on domestic goods and services at a given price level. Its components are consumption (C), investment (I), government spending (G), and net exports (X − M).
总需求 (AD) 是在特定价格水平下，对国内商品和服务的总支出。其组成部分为消费 (C)、投资 (I)、政府支出 (G) 和净出口 (X − M)。
Fiscal policy involves changes in government spending and taxation to influence AD. The government budget balance is:
财政政策通过改变政府支出和税收来影响总需求。政府预算平衡为：
Budget balance = Tax revenue − Government spending
预算平衡 = 税收收入 − 政府支出
Monetary policy uses interest rates and money supply to manage inflation and support growth. The relationship between real and nominal interest rates (simplified) is:
货币政策利用利率和货币供应量来管理通胀并支持增长。实际利率与名义利率的关系（简化版）是：
Real interest rate ≈ Nominal interest rate − Inflation rate
实际利率 ≈ 名义利率 − 通胀率
Exchange rates determine the price of one currency in terms of another. A depreciation makes exports cheaper and imports dearer, boosting AD; an appreciation has the opposite effect.
汇率决定了一种货币以另一种货币表示的价格。贬值会使出口变便宜、进口变贵，从而刺激总需求；升值则产生相反效果。
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