📚 Year 7 AQA Economics: Formula & Theorem Quick Reference Handbook | Year 7 AQA 经济：公式定理速查手册
This quick reference handbook provides all the essential formulas and theorems for Year 7 AQA Economics. Whether you are revising key concepts like scarcity, demand and supply, or calculating costs, revenues and profit, this bilingual guide will help you master the fundamentals step by step. Use it to check definitions, reinforce understanding and build confidence before assessments.
本速查手册涵盖 Year 7 AQA 经济所有核心公式与定理。无论你是在复习稀缺性、需求与供给等关键概念，还是在计算成本、收入与利润，这份中英双语指南都能帮助你逐步掌握基础知识。你可以用它查定义、巩固理解、在测评前建立信心。
1. Scarcity and Opportunity Cost | 稀缺性与机会成本
Scarcity means our unlimited wants are greater than the limited resources available. Because we cannot have everything, we must make choices. Economics studies how people, businesses and governments make these choices to allocate scarce resources efficiently.
稀缺性意味着我们无限的欲望超过了有限的资源。由于无法拥有一切，我们必须做出选择。经济学研究个人、企业和政府如何做出这些选择以有效配置稀缺资源。
The opportunity cost of a choice is the value of the next best alternative that you give up. For example, if a student chooses to study economics instead of playing football, the opportunity cost is the enjoyment and health benefits of playing football. Opportunity cost is a key concept behind every economic decision.
某一选择的机会成本是你所放弃的次优选择的价值。例如，如果一名学生选择学习经济而不是踢足球，那么机会成本就是踢足球所带来的乐趣和健康益处。机会成本是每个经济决策背后的关键概念。
| Concept | Explanation |
| Scarcity | Limited resources vs unlimited wants |
| Choice | Deciding how to use limited resources |
| Opportunity Cost | The next best alternative foregone |
Opportunity Cost = Value of Next Best Alternative Foregone
机会成本 = 所放弃的次优选择的价值
2. Demand and the Law of Demand | 需求与需求定律
Demand is the quantity of a good or service that consumers are willing and able to buy at different prices during a given period. It reflects both desire and purchasing power. A demand schedule shows how quantity demanded changes with price, and a demand curve is its graphical representation, typically sloping downwards.
需求是指在一定时期内，消费者在不同价格水平上愿意并且能够购买的商品或服务的数量。它既反映了购买意愿，也体现了购买力。需求表显示需求量如何随价格变化，需求曲线是其图形表示，通常向右下方倾斜。
The law of demand states that, ceteris paribus (all other factors unchanged), as the price of a good rises, the quantity demanded falls, and as price falls, quantity demanded rises. This inverse relationship is due to the substitution effect and the income effect.
需求定律指出，在其他条件不变的情况下，当商品价格上升时，需求量下降；当价格下降时，需求量上升。这种反向关系源于替代效应和收入效应。
Factors that shift the demand curve include changes in income, tastes, prices of related goods (substitutes and complements), and expectations. A rightward shift means more is demanded at each price; a leftward shift means less.
导致需求曲线移动的因素包括收入变化、偏好改变、相关商品（替代品和互补品）价格变化以及预期变化。需求曲线向右移动意味着每个价格下需求量增加；向左移动则减少。
- Law of Demand: P ↑ → Qd ↓ / P ↓ → Qd ↑
- 需求定律：价格上升 → 需求量下降 / 价格下降 → 需求量上升
3. Supply and the Law of Supply | 供给与供给定律
Supply is the quantity of a good or service that producers are willing and able to offer for sale at different prices during a given period. Firms supply more at higher prices because greater potential profit encourages them to increase output.
供给是指在一定时期内，生产者在不同价格水平上愿意并且能够出售的商品或服务的数量。价格越高，企业供给越多，因为更大的潜在利润激励它们增加产出。
The law of supply says that, ceteris paribus, as price rises, the quantity supplied increases, and as price falls, quantity supplied decreases. This results in an upward‑sloping supply curve.
供给定律指出，在其他条件不变的情况下，价格上升时，供给量增加；价格下降时，供给量减少。因而供给曲线向右上方倾斜。
Shifts in supply are caused by factors such as production costs, technology, taxes and subsidies, and the number of sellers. A rightward shift indicates an increase in supply at every price, while a leftward shift indicates a decrease.
供给的移动受生产成本、技术、税收与补贴、以及卖者数量等因素影响。供给曲线向右移动表示每个价格下供给增加，向左移动则表示供给减少。
- Law of Supply: P ↑ → Qs ↑ / P ↓ → Qs ↓
- 供给定律：价格上升 → 供给量增加 / 价格下降 → 供给量减少
4. Market Equilibrium | 市场均衡
Market equilibrium occurs at the price where quantity demanded equals quantity supplied. At this point, there is no tendency for price to change, and the market is cleared. The equilibrium price is often called the market‑clearing price, and the corresponding quantity is the equilibrium quantity.
市场均衡出现在需求量等于供给量的价格水平上。此时价格没有变动的倾向，市场出清。均衡价格常被称为市场出清价格，对应的数量则是均衡数量。
If the market price is above equilibrium, a surplus (excess supply) exists, which puts downward pressure on price. If the price is below equilibrium, a shortage (excess demand) drives price upward. The interaction of demand and supply automatically pushes the market toward equilibrium.
若市场价格高于均衡水平，就会出现过剩（超额供给），对价格产生向下的压力；若价格低于均衡水平，则出现短缺（超额需求），推动价格上升。供求的相互作用会自动将市场推向均衡。
Equilibrium Condition: Qd = Qs
均衡条件：需求量 = 供给量
| Situation | Price relative to equilibrium | Market outcome |
| Surplus | Above equilibrium | Downward pressure on price |
| Shortage | Below equilibrium | Upward pressure on price |
| Equilibrium | At equilibrium price | No pressure for price change |
5. Price Elasticity of Demand (PED) | 需求的价格弹性 (PED)
Price elasticity of demand measures how responsive quantity demanded is to a change in price. It is calculated as the percentage change in quantity demanded divided by the percentage change in price.
需求的价格弹性衡量需求量对价格变化的反应程度。它的计算方法是需求量变动的百分比除以价格变动的百分比。
PED = (% Change in Quantity Demanded) ÷ (% Change in Price)
PED = (需求量变动%) ÷ (价格变动%)
If PED > 1, demand is elastic — consumers are very sensitive to price changes. If PED < 1, demand is inelastic — PED of zero means perfectly inelastic demand, while infinite PED means perfectly elastic.
若 PED > 1，需求富有弹性——消费者对价格变化很敏感。若 PED < 1，需求缺乏弹性——消费者不太敏感。若 PED = 1，需求为单位弹性。PED 为 0 表示完全无弹性，无穷大则表示完全有弹性。
Determinants of PED include the availability of substitutes, whether the good is a necessity or luxury, the proportion of income spent on it, and the time period considered.
PED 的决定因素包括替代品的可得性、商品是必需品还是奢侈品、支出占收入的比例以及所考虑的时间长短。
- Elastic demand: |PED| > 1 → Price rise → total revenue falls
- Inelastic demand: |PED| < 1 → Price rise → total revenue rises
- 富有弹性：|PED| > 1 → 提价 → 总收入下降
- 缺乏弹性：|PED| < 1 → 提价 → 总收入上升
6. Costs of Production | 生产成本
Firms incur costs when producing goods and services. Total cost (TC) is the sum of all expenses involved in production. It is divided into fixed costs (FC), which do not vary with output, and variable costs (VC), which change with the level of production.
企业生产商品和服务时会产生成本。总成本 (TC) 是生产中全部费用的总和，分为固定成本 (FC) 和变动成本 (VC)。固定成本不随产量变化，变动成本则随生产水平变化。
Total Cost = Fixed Cost + Variable Cost
总成本 = 固定成本 + 变动成本
Average total cost (ATC) is the cost per unit of output. It is found by dividing total cost by the quantity produced. Marginal cost (MC) is the additional cost of producing one more unit.
平均总成本 (ATC) 是每单位产出的成本，等于总成本除以产量。边际成本 (MC) 是额外生产一单位产品所增加的成本。
ATC = TC ÷ Q and MC = Change in TC ÷ Change in Q
平均总成本 = 总成本 ÷ 数量 边际成本 = 总成本的变化 ÷ 数量的变化
7. Revenue | 收入
Revenue is the income a firm receives from selling its goods or services. Total revenue (TR) is calculated by multiplying the price per unit by the quantity sold. Average revenue (AR) is revenue per unit, which equals price.
收入是企业通过销售商品或服务获得的所得。总收入 (TR) 等于每单位价格乘以销售量。平均收入 (AR) 是每单位收入，等于价格。
Total Revenue = Price × Quantity Sold
总收入 = 价格 × 销售量
Average Revenue = TR ÷ Q = Price
平均收入 = 总收入 ÷ 数量 = 价格
Understanding revenue helps firms make pricing decisions. If demand is elastic, lowering price can increase total revenue; if demand is inelastic, raising price can increase total revenue.
理解收入有助于企业进行定价决策。若需求富有弹性，降低价格可增加总收入；若需求缺乏弹性，提高价格则可增加总收入。
8. Profit | 利润
Profit is the difference between total revenue and total cost. It is the reward entrepreneurs receive for taking risks. Profit can be normal profit (the minimum needed to keep resources in their current use) or supernormal profit (profit above normal profit).
利润是总收入与总成本之间的差额，是企业家承担风险所获得的回报。利润可分为正常利润（维持资源现有用途所需的最低回报）和超常利润（超过正常利润的部分）。
Profit = Total Revenue − Total Cost
利润 = 总收入 − 总成本
it is zero. Negative profit is called a loss. Businesses aim to maximise profit by managing costs and choosing optimal output levels.
当总收入等于总成本时，企业达到盈亏平衡，此时利润为零。负利润称为亏损。企业通过管理成本、选择最优产量来实现利润最大化。
9. Production Possibility Frontier (PPF) | 生产可能性边界 (PPF)
The production possibility frontier shows the maximum possible combinations of two goods or services an economy can produce with its available resources and technology. Points on the PPF are efficient, points inside are inefficient, and points outside are unattainable given current resources.
生产可能性边界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或服务的最大可能组合。边界上的点代表有效率的生产，边界内的点代表无效率，边界外的点在现有资源下无法实现。
The shape of the PPF reflects opportunity cost. A straight‑line PPF implies constant opportunity cost, while a concave (bowed‑outward) PPF indicates increasing opportunity cost — as more of one good is produced, larger amounts of the other must be sacrificed.
PPF 的形状反映了机会成本。直线的 PPF 意味着机会成本不变，而凹向原点的 PPF 则表示机会成本递增——当生产更多的一种商品时，就必须牺牲更多的另一种商品。
Economic growth shifts the PPF outward when the quantity or quality of resources improves, or when technology advances. Recessions or natural disasters can shift it inward.
当资源数量或质量提高，或技术进步时，经济增长会使 PPF 向外移动。经济衰退或自然灾害则可能使其向内移动。
- Point on PPF: efficient use of resources
- Point inside PPF: underutilisation of resources
- Point outside PPF: not currently achievable
- PPF上的点：资源有效利用
- PPF内的点：资源未充分利用
- PPF外的点：当前无法实现
10. Functions of Money | 货币的功能
Money serves four main functions in an economy: it acts as a medium of exchange, a unit of account, a store of value, and a standard of deferred payment. These functions make trade and saving much easier compared to a barter system.
货币在经济中发挥四项主要功能：交换媒介、计价单位、价值储藏和延期支付标准。与物物交换相比，这些功能使交易和储蓄变得极为便利。
Medium of exchange: Money is widely accepted for buying and selling goods and services, eliminating the need for a double coincidence of wants. Unit of account: Prices are quoted in monetary terms, allowing easy comparison of value. Store of value: Money can be saved and used later without losing much purchasing power, provided inflation is low. Standard of deferred payment: Debts and future payments are expressed in money, enabling credit and loans.
交换媒介：货币被广泛用于买卖商品和服务，避免了双重需求巧合。计价单位：价格用货币标注，便于比较价值。价值储藏：只要通胀较低，货币可以储存并在未来使用而不过多丧失购买力。延期支付标准：债务和未来付款都以货币表示，使信用和贷款成为可能。
| Function | What it means |
| Medium of exchange | Used to buy and sell goods |
| Unit of account | Measures the value of goods |
| Store of value | Holds value over time |
| Standard of deferred payment | Allows borrowing and lending |
11. Interest Rates and Savings | 利率与储蓄
Interest is the cost of borrowing money or the reward for saving. The interest rate is usually expressed as a percentage of the principal (the amount borrowed or saved) per year. Simple interest is calculated on the original principal only.
利息是借钱的成本或储蓄的回报。利率通常表示为每年本金（借入或存入的金额）的百分比。单利仅按原始本金计算。
Simple Interest = Principal × Rate × Time (in years)
单利 = 本金 × 利率 × 时间（年）
For example, saving £100 at 5% simple interest for 3 years yields £15 in interest, so the total amount becomes £115. In compound interest, each year’s interest is added to the principal, so interest is earned on previously accumulated interest. Compound interest grows savings faster over time.
例如，以 5% 的年单利储蓄 100 英镑，3 年可获得 15 英镑利息，总额变为 115 英镑。而复利是将每年的利息加入本金，从而对已积累的利息也计算利息。随着时间推移，复利使储蓄增长更快。
Higher interest rates encourage saving and discourage borrowing; lower interest rates tend to stimulate borrowing and spending. Central banks adjust the base interest rate to help manage inflation and economic growth.
较高的利率鼓励储蓄、抑制借贷；较低的利率则倾向于刺激借贷和消费。央行通过调整基准利率来帮助管理通胀和经济增长。
12. Basic Economic Indicators | 基本经济指标
Economies are measured by indicators such as Gross Domestic Product (GDP), inflation, and unemployment. GDP is the total value of all final goods and services produced in a country in one year. GDP per capita divides GDP by the population and gives an average output per person.
经济体的表现通过国内生产总值 (GDP)、通货膨胀和失业率等指标来衡量。GDP 是一国在一年内生产的所有最终商品和服务的总价值。人均 GDP 是 GDP 除以人口，反映人均产出。
GDP per capita = GDP ÷ Population
人均 GDP = GDP ÷ 人口
Inflation is the sustained rise in the general price level. It is measured by the annual percentage change in a price index such as the Consumer Price Index (CPI). Low and stable inflation is usually a target for governments and central banks.
通货膨胀是物价总水平的持续上涨，通常通过消费者价格指数 (CPI) 等价格指数的年变动百分比来衡量。低而稳定的通胀通常是政府和央行的目标。
Unemployment rate measures the percentage of the labour force that is willing and able to work but cannot find a job. These indicators help policymakers assess economic health and design appropriate responses.
失业率衡量劳动力中愿意且有能力工作但无法找到工作的人所占的百分比。这些指标帮助政策制定者评估经济健康状况并制定相应对策。
- GDP growth: signals economic expansion or contraction
- Inflation rate: signals rising cost of living
- Unemployment rate: signals underutilisation of labour
- GDP 增长：显示经济扩张或收缩
- 通胀率：显示生活成本上升
- 失业率：显示劳动力利用不足
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