📚 Year 8 SQA Economics: Quick Reference Handbook of Formulas and Theorems | 八年级SQA经济：公式定理速查手册
This handbook provides a concise summary of essential formulas, key theorems and core economic concepts for Year 8 students following the SQA curriculum in Scotland. It is designed for quick revision, helping you understand and apply basic economic principles effectively.
本手册为苏格兰SQA课程八年级学生提供了基本公式、关键定理和核心经济概念的简明总结。它旨在帮助快速复习，有效理解和应用基本经济原理。
1. The Basic Economic Problem: Scarcity | 基本经济问题：稀缺性
Scarcity is the fundamental economic problem that arises because resources are limited while human wants are infinite. This means we cannot have everything we desire, forcing individuals, businesses and governments to make choices.
稀缺性是基本经济问题，它源于资源有限而人的欲望无限。这意味着我们无法拥有所有想要的东西，从而迫使个人、企业和政府做出选择。
rtunity Cost. The existence of scarcity means that every decision involves giving up something else.
关键定理：稀缺性 → 选择 → 机会成本。稀缺性的存在意味着每一个决定都涉及放弃其他东西。
The basic economic questions every society must answer are: "What to produce?", "How to produce?" and "For whom to produce?"
每个社会必须回答的基本经济问题是："生产什么？"、"如何生产？"以及"为谁生产？"
2. Opportunity Cost | 机会成本
Opportunity cost is the value of the next best alternative forgone when a choice is made. It represents the sacrifice of the most desired option that is not chosen.
机会成本是做出选择时所放弃的次优选择的价值。它代表了未被选择的最渴望选项的牺牲。
Opportunity Cost = Value of the Next Best Alternative Forgone
机会成本 = 放弃的次优选择的价值
For example, if you have £10 and choose to buy a cinema ticket instead of a new notebook, the opportunity cost is the value and usefulness you would have gained from the notebook.
例如，如果你有10英镑，选择购买一张电影票而不是一个新笔记本，那么机会成本就是你原本可以从笔记本中获得的价值和用处。
3. 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 over a given period of time.
需求是在给定时间内，消费者在不同价格水平下愿意且能够购买的商品或服务的数量。
The law of demand states that, ceteris paribus (all other factors unchanged), as the price of a good increases, the quantity demanded decreases; conversely, as the price decreases, the quantity demanded increases.
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；反之，价格下降时需求量上升。
Example Demand Schedule
需求表示例
| Price per unit (£) | Quantity Demanded (units) |
|---|---|
| 1 | 100 |
| 2 | 80 |
| 3 | 60 |
| 4 | 40 |
| 5 | 20 |
The inverse relationship between price and quantity demanded gives the demand curve its downward slope.
价格与需求量之间的反向关系使得需求曲线呈向下倾斜。
4. 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 over a given period of time.
供给是在给定时间内，生产者在不同价格水平下愿意且能够提供出售的商品或服务的数量。
The law of supply states that, ceteris paribus, as the price of a good increases, the quantity supplied increases; as the price decreases, the quantity supplied decreases.
供给定律指出，在其他条件不变的情况下，商品价格上升时供给量增加；价格下降时供给量减少。
Example Supply Schedule
供给表示例
| Price per unit (£) | Quantity Supplied (units) |
|---|---|
| 1 | 10 |
| 2 | 30 |
| 3 | 50 |
| 4 | 70 |
| 5 | 90 |
This positive relationship between price and quantity supplied means the supply curve slopes upward.
价格与供给量之间的正向关系意味着供给曲线向上倾斜。
5. Market Equilibrium | 市场均衡
Market equilibrium occurs at the price where the quantity demanded by consumers exactly equals the quantity supplied by producers. At this point, there is no tendency for price to change, and the market is in balance.
市场均衡出现在消费者需求量与生产者供给量正好相等的价格水平上。此时价格没有变化的趋势，市场处于平衡状态。
Equilibrium Condition: Qd = Qs
均衡条件：需求量 = 供给量
The equilibrium price (Pe) is also called the market-clearing price. If price is above equilibrium, a surplus exists; if below, a shortage occurs. In both cases, market forces will push the price back toward Pe.
均衡价格（Pe）也称市场出清价格。如果价格高于均衡，就会出现过剩；如果低于均衡，就会出现短缺。在这两种情况下，市场力量都会将价格推回至Pe。
6. Revenue, Costs and Profit | 收入、成本与利润
Total Revenue (TR) is the money a firm receives from selling its products. It is calculated by multiplying the selling price per unit by the quantity sold.
总收入（TR）是企业从销售产品中获得的货币。它通过单位售价乘以销售数量来计算。
Total Revenue = Price × Quantity Sold
总收入 = 价格 × 销售数量
Total Cost (TC) is the sum of all expenses incurred in production. It equals total fixed costs plus total variable costs.
总成本（TC）是生产中发生的所有费用的总和。它等于总固定成本加上总可变成本。
Total Cost = Total Fixed Cost + Total Variable Cost
总成本 = 总固定成本 + 总可变成本
Average Cost (AC) is the cost per unit of output.
平均成本（AC）是每单位产出的成本。
Average Cost = Total Cost ÷ Quantity
平均成本 = 总成本 ÷ 数量
Profit is the financial gain when total revenue exceeds total cost. If TC is greater than TR, the firm makes a loss.
利润是总收入超过总成本时的财务收益。如果总成本大于总收入，企业就发生亏损。
Profit = Total Revenue − Total Cost
利润 = 总收入 − 总成本
The break-even point is where total revenue exactly equals total cost, resulting in neither profit nor loss. The break-even quantity can be found using the contribution per unit.
盈亏平衡点是总收入恰好等于总成本，不赚不亏。盈亏平衡产量可以用单位贡献额来计算。
ntity = Total Fixed Costs ÷ (Selling Price per Unit − Variable Cost per Unit)
盈亏平衡产量 = 总固定成本 ÷（单位售价 − 单位可变成本）
7. Factors of Production, Production and Productivity | 生产要素、生产与生产率
The four factors of production are land (natural resources), labour (human effort), capital (man-made tools and machinery) and enterprise (the skill of organising the other factors and taking risks).
四种生产要素是土地（自然资源）、劳动（人力）、资本（人造工具和机器）和企业精神（组织其他要素并承担风险的技能）。
Production is the process of converting inputs into outputs of goods and services. Productivity measures how efficiently inputs are turned into outputs.
生产是将投入转化为商品和服务产出的过程。生产率衡量投入转化为产出的效率。
A key measure is labour productivity, which shows output per worker or per hour worked.
一个关键指标是劳动生产率，它显示每名工人或每工作小时的产出。
Productivity = Total Output ÷ Total Input
生产率 = 总产出 ÷ 总投入
Improving productivity allows firms to produce more with the same resources, which can reduce average costs and increase profits.
提高生产率使企业能够用同样的资源生产更多产品，这样可以降低平均成本并增加利润。
8. The Circular Flow of Income | 收入循环流动
The circular flow model shows how money and resources move between two key sectors of the economy: households and firms.
循环流动模型展示了货币和资源如何在经济体的两个关键部门——家庭和厂商——之间流动。
Households supply factors of production (land, labour, capital, enterprise) to firms and in return receive income in the form of wages, rent, interest and profit.
家庭向厂商提供生产要素（土地、劳动、资本、企业精神），并以此换取工资、地租、利息和利润等收入。
Firms use these factors to produce goods and services, which they then sell to households. Households spend their income on these goods and services, creating a continuous flow.
厂商利用这些要素生产商品和服务，然后将其出售给家庭。家庭在这些商品和服务上花费收入，从而形成了持续的流动。
The inner loop represents the real flow of factors and goods, while the outer loop represents the monetary flow of incomes and spending.
内圈代表要素和商品的实际流动，而外圈代表收入和支出的货币流动。
9. Inflation and the Purchasing Power of Money | 通货膨胀与货币购买力
Inflation is a sustained increase in the general price level of goods and services in an economy over time. When inflation occurs, each unit of currency buys fewer goods and services.
通货膨胀是指一个经济体中商品和服务的总体价格水平持续上升。通货膨胀发生时，每一单位货币能购买的商品和服务减少。
Purchasing power is the quantity of goods and services that can be bought with a given amount of money. It is inversely related to the average price level.
购买力是指用给定数量的货币可以购买的商品和服务的数量。它与平均价格水平呈反比关系。
Purchasing Power = 1 ÷ Average Price Level
购买力 = 1 ÷ 平均价格水平
For example, if the price level doubles, the purchasing power of money halves, meaning your £10 now buys only what £5 used to buy.
例如，如果价格水平翻一番，货币的购买力就减半，意味着你的10英镑现在只能买到过去5英镑的东西。
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