📚 Year 8 CCEA Economics: Formula & Theorem Quick Reference Guide | 8 年级 CCEA 经济：公式定理速查手册
Welcome to your Year 8 Economics quick reference handbook. This guide collects the essential formulas, theorems and core definitions you will meet in CCEA Key Stage 3 Economics. Use it to revise, test yourself and build strong foundations for future study.
欢迎使用 8 年级经济速查手册。本手册汇集了 CCEA 关键阶段 3 经济课程中必须掌握的公式、定理和核心定义。用它来复习、自测，为今后的学习打下扎实基础。
1. Scarcity and Choice | 稀缺性与选择
The basic economic problem arises because people have unlimited wants but resources are limited. This forces individuals, businesses and governments to make choices.
基本经济问题源于人类的欲望无限但资源有限。这迫使个人、企业和政府做出选择。
Scarcity means there are not enough goods and services to satisfy everyone's wants. Every choice involves giving something up.
稀缺意味着没有足够的商品和服务来满足所有人的欲望。每一个选择都意味着放弃某些东西。
2. Opportunity Cost | 机会成本
Opportunity cost is the value of the next best alternative that is given up when a choice is made. It is not just money spent, but also time, effort or enjoyment lost.
机会成本是指做出选择时所放弃的次优方案的价值。它不只是花费的金钱，还包括失去的时间、精力或乐趣。
When a student decides to spend an hour revising Economics instead of playing video games, the opportunity cost is the enjoyment given up by not gaming.
当学生决定花一小时复习经济而不是玩电子游戏时，机会成本就是放弃打游戏所带来的乐趣。
3. Factors of Production | 生产要素
Resources are grouped into four factors of production: Land (natural resources), Labour (human effort), Capital (man‑made tools and machinery) and Enterprise (the ability to organise the other three and take risks).
资源被分为四种生产要素：土地（自然资源）、劳动（人力付出）、资本（人造工具和机器）以及企业家才能（组织其他三要素并承担风险的能力）。
The reward for each factor: Land earns rent, Labour earns wages, Capital earns interest, and Enterprise earns profit.
各要素的报酬：土地获得租金，劳动获得工资，资本获得利息，企业家才能获得利润。
4. Law of Demand | 需求定律
The law of demand states that, ceteris paribus, as the price of a good rises, the quantity demanded falls, and as price falls, quantity demanded rises. There is an inverse relationship between price and quantity demanded.
需求定律指出，在其他条件不变的情况下，商品价格上升，需求量下降；价格下降，需求量上升。价格与需求量之间呈反向关系。
A change in the good's own price causes a movement along the demand curve, while changes in income, tastes, prices of related goods or expectations shift the whole demand curve.
商品自身价格的变化导致沿需求曲线的移动，而收入、偏好、相关商品价格或预期的变化会使整条需求曲线位移。
5. Law of Supply | 供给定律
The law of supply states that, ceteris paribus, as the price of a good rises, the quantity supplied rises, and as price falls, quantity supplied falls. There is a direct relationship between price and quantity supplied.
供给定律指出，在其他条件不变的情况下，商品价格上升，供给量上升；价格下降，供给量下降。价格与供给量之间呈正向关系。
A change in the good's own price leads to a movement along the supply curve; changes in costs of production, technology, taxes or subsidies shift the supply curve.
商品自身价格的变化导致沿供给曲线的移动；生产成本、技术、税收或补贴的变化会使供给曲线位移。
6. Market Equilibrium | 市场均衡
Market equilibrium occurs where the quantity demanded equals the quantity supplied. At this point there is no excess demand or excess supply, and the market is cleared.
市场均衡出现在需求量等于供给量之处。此时没有超额需求或超额供给，市场出清。
Equilibrium price and quantity are found at the intersection of the demand and supply curves. If price is above equilibrium, a surplus arises; if below, a shortage arises.
均衡价格与均衡数量位于需求曲线和供给曲线的交点。若价格高于均衡水平，出现过剩；低于均衡水平，出现短缺。
7. Price Elasticity of Demand (Simple) | 需求价格弹性（简易）
Price elasticity of demand (PED) measures how responsive quantity demanded is to a change in price. It can be elastic (responsive), inelastic (unresponsive) or unit elastic.
需求价格弹性衡量需求量对价格变化的反应程度。它可以是富弹性的（敏感）、欠弹性的（不敏感）或单位弹性的。
A basic formula for PED: Percentage change in quantity demanded ÷ Percentage change in price. For Year 8, it is enough to know that necessities tend to be inelastic while luxuries tend to be elastic.
需求价格弹性的基本公式：需求量变动的百分比 ÷ 价格变动的百分比。对于 8 年级，知道必需品往往缺乏弹性而奢侈品富有弹性就已足够。
8. Costs, Revenue and Profit | 成本、收入与利润
Firms aim to make a profit. Total Revenue is the money a firm receives from selling its goods or services.
企业以赚取利润为目标。总收入是企业销售商品或服务获得的全部货币。
Total Revenue (TR) = Price (P) × Quantity sold (Q)
总收入 (TR) = 单价 (P) × 销售量 (Q)
Total Cost includes all the expenses of production. It is split into Fixed Costs (do not change with output, e.g. rent) and Variable Costs (change with output, e.g. raw materials).
总成本包括所有生产费用。它分为固定成本（不随产量变动，如租金）和变动成本（随产量变动，如原材料）。
Total Cost (TC) = Fixed Cost (FC) + Variable Cost (VC)
总成本 (TC) = 固定成本 (FC) + 变动成本 (VC)
Average Cost is the cost of producing one unit. Profit is the difference between total revenue and total cost.
平均成本是生产一单位产品的成本。利润是总收入与总成本的差额。
Average Cost (AC) = TC ÷ Q
平均成本 (AC) = 总成本 (TC) ÷ 产量 (Q)
Profit = TR − TC
利润 = 总收入 (TR) − 总成本 (TC)
9. Economic Growth and GDP | 经济增长与 GDP
Economic growth is an increase in a country's output of goods and services over time. It is usually measured by the Gross Domestic Product (GDP).
经济增长是指一个国家商品和服务产出随着时间的推移而增加。它通常用国内生产总值（GDP）来衡量。
GDP is the total value of all final goods and services produced within a country in a year. Real GDP takes inflation into account to show true growth.
GDP 是一国在一年内生产的所有最终商品和服务的总价值。实际 GDP 扣除了通货膨胀的影响，以反映真实增长。
GDP₁) ÷ GDP₁ × 100. Sustainable growth avoids harming the environment or future resources.
增长可用百分比变动表示：(GDP₂ − GDP₁) ÷ GDP₁ × 100。可持续增长避免损害环境或未来的资源。
10. Inflation | 通货膨胀
Inflation is a sustained rise in the general price level of goods and services in an economy over time. It reduces the purchasing power of money.
通货膨胀是指一个经济体中商品和服务总体价格水平在一段时间内持续上升。它降低了货币的购买力。
It is measured by the Consumer Price Index (CPI) or the Retail Price Index (RPI). A low and stable rate of inflation (often around 2%) is a common government target.
它通过消费者物价指数（CPI）或零售物价指数（RPI）来测量。低而稳定的通胀率（通常约为 2%）是常见的政府目标。
11. Employment and Unemployment | 就业与失业
Unemployment occurs when people who are willing and able to work cannot find a job. The unemployment rate is the percentage of the labour force that is unemployed.
失业是指愿意并且有能力工作的人找不到工作。失业率是劳动力中失业人口所占的百分比。
s not mean zero unemployment; there is always some frictional and structural unemployment.
失业率的简单公式：(失业人数 ÷ 劳动力) × 100。充分就业并不意味着零失业，总存在一些摩擦性和结构性失业。
12. International Trade Basics | 国际贸易基础
Countries trade because they have different resources and can specialise in producing goods where they have a comparative advantage. Exports are goods sold abroad; imports are goods bought from abroad.
国家之间进行贸易是因为它们拥有不同的资源，并且可以专门生产具有比较优势的商品。出口是卖给国外的商品；进口是从国外购买的商品。
The balance of trade is the difference between the value of a country's exports and imports. A trade surplus occurs when exports > imports; a trade deficit occurs when imports > exports.
贸易差额是一国出口值与进口值之间的差额。当出口大于进口时出现贸易顺差；当进口大于出口时出现贸易逆差。
Exchange rates influence trade: a weaker home currency makes exports cheaper and imports dearer; a stronger currency does the opposite.
汇率影响贸易：本币贬值使出口更便宜、进口更贵；本币升值则相反。
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