📚 Year 8 AQA Economics: Formula & Theorem Quick Reference Guide | Year 8 AQA 经济：公式定理速查手册
Welcome to your go-to revision handbook for Year 8 AQA Economics. This guide collects the essential formulas, theorems and core concepts you need to master the subject. Each section presents a key idea in clear English, immediately followed by its Chinese translation, so you can learn bilingually and reinforce your understanding. Use this handbook to quickly recall definitions, practise calculations and build confidence before tests.
欢迎使用这本 Year 8 AQA 经济速查手册。本手册汇集了你必须掌握的核心公式、定理与关键概念。每个小节先用简明的英文阐述一个要点，紧接着提供中文翻译，帮助你用双语学习并加深理解。你可以用它快速回忆定义、练习计算、并在考试前建立信心。
1. Scarcity and the Basic Economic Problem | 稀缺性与基本经济问题
The fundamental economic problem is scarcity: there are finite resources but unlimited human wants. This forces individuals, firms and governments to make choices about how to allocate resources.
基本经济问题是稀缺性：资源有限，而人类的欲望无限。这迫使个人、企业和政府必须就如何分配资源做出选择。
Because of scarcity, every choice involves an opportunity cost. The true cost of any decision is not just the money spent, but the value of the next best alternative that is given up.
由于稀缺性的存在，每个选择都涉及机会成本。任何决策的真实成本不仅包括货币支出，还包括所放弃的次优选择的价值。
Scarcity is permanent; shortages are temporary. Scarcity exists in all economies, regardless of wealth, because wants always exceed available resources.
稀缺性是永恒的，短缺则是暂时的。无论贫富，所有经济体都存在稀缺性，因为欲望永远超过可用资源。
2. Opportunity Cost | 机会成本
Opportunity cost is defined as the value of the next best alternative foregone when a choice is made. It is a core concept that helps explain why trade-offs exist and why decision-making always involves a sacrifice.
机会成本被定义为做出一个选择时所放弃的次优选择的价值。这是一个核心概念，有助于解释为什么存在权衡取舍，以及为什么决策总是包含某种牺牲。
For example, if a government spends £10 million on a new motorway, the opportunity cost is the healthcare or education programme that could have been funded with that same money.
例如，如果政府花费 1000 万英镑修建一条新高速公路，那么机会成本就是本可以用同一笔资金资助的医疗或教育项目。
Opportunity cost is not always measured in money; it can also be measured in time, enjoyment or other non-monetary terms.
机会成本并不总是以金钱衡量；它也可以用时间、享受或其他非货币尺度来计量。
3. Law of Demand and Total Expenditure | 需求定律与总支出
The law of demand states that, ceteris paribus (all other things being equal), as the price of a good or service rises, the quantity demanded falls, and vice versa. This inverse relationship gives the demand curve its downward slope.
需求定律指出，在其他条件不变的情况下，商品或服务的价格上升时，需求量会下降；反之亦然。这种反向关系使需求曲线向下倾斜。
Consumers react to price changes because of two effects: the substitution effect (consumers switch to cheaper alternatives) and the income effect (a price rise reduces real purchasing power).
消费者对价格变动做出反应源于两种效应：替代效应（消费者转向更便宜的替代品）和收入效应（价格上涨会降低实际购买力）。
Total expenditure by consumers on a product is calculated using the formula:
消费者在一种产品上的总支出可以通过以下公式计算：
Total Expenditure = Price × Quantity Demanded
总支出 = 价格 × 需求量
This formula also represents the total revenue received by firms when the quantity sold equals quantity demanded at a given price.
这个公式同样表示当销售量等于给定价格下的需求量时，企业获得的总收入。
4. Law of Supply and Total Revenue | 供给定律与总收益
The law of supply states that, ceteris paribus, as the price of a good or service rises, the quantity supplied increases. Producers are willing to offer more because higher prices can cover rising production costs and generate greater potential profit.
供给定律指出，在其他条件不变的情况下，商品或服务的价格上升时，供给量会增加。生产者愿意提供更多，因为更高的价格能够覆盖上升的生产成本并带来更多的潜在利润。
The supply curve typically slopes upwards. Profit motive is the key driver: when the market price rises, existing firms expand output and new firms may enter the market.
供给曲线通常向上倾斜。利润动机是关键驱动因素：当市场价格上升时，现有企业会扩大产出，新企业也可能进入市场。
Total revenue (TR) is the income a firm receives from selling its products. The basic formula is:
总收益 (TR) 是企业销售产品所获得的收入。基本公式为：
Total Revenue = Price × Quantity Sold
总收益 = 价格 × 销售数量
In equilibrium, the quantity sold equals the quantity demanded, so total revenue equals total expenditure. Understanding this link is essential for analysing market transactions.
在均衡状态下，销售数量等于需求量，因此总收益等于总支出。理解这一联系对于分析市场交易至关重要。
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 excess demand or excess supply, and the market clears.
市场均衡发生在消费者愿意购买的数量恰好等于生产者愿意出售的数量的价格水平上。此时，既不存在超额需求，也不存在超额供给，市场得以出清。
The equilibrium condition can be expressed as:
均衡条件可以表示为：
Qd = Qs
需求量 = 供给量
If the price is above equilibrium, a surplus occurs, putting downward pressure on price. If the price is below equilibrium, a shortage arises, pushing price upwards. These forces drive the market back to equilibrium.
如果价格高于均衡水平，会出现过剩，给价格带来下行压力；如果价格低于均衡水平，会出现短缺，推动价格上升。这些力量促使市场回到均衡状态。
6. Price Elasticity of Demand (PED) | 需求价格弹性
Price elasticity of demand measures how responsive the quantity demanded is to a change in price. It helps economists predict how a price change will affect total revenue and consumer behaviour.
需求价格弹性衡量需求量对价格变动的反应程度。它有助于经济学家预测价格变动将如何影响总收益和消费者行为。
The PED formula is:
PED 的计算公式为：
PED = %Δ in Quantity Demanded ÷ %Δ in Price
PED = 需求量的百分比变化 ÷ 价格的百分比变化
ice. If PED < 1, demand is price inelastic, and total revenue moves in the same direction as price. If PED = 1, demand is unit elastic.
如果 PED > 1，需求富有价格弹性：需求量变动的百分比大于价格变动的百分比，总收益与价格逆向变动。如果 PED < 1，需求缺乏价格弹性，总收益与价格同向变动。如果 PED = 1，需求为单位弹性。
Factors influencing PED include the availability of substitutes, whether the good is a necessity or a luxury, and the time period considered.
影响 PED 的因素包括替代品的可获得性、商品是必需品还是奢侈品，以及所考虑的时间跨度。
7. Costs, Revenue and Profit | 成本、收益与利润
A firm's profit is the reward for risk-taking and the key driver of production decisions. It is calculated as the difference between total revenue and total cost.
企业的利润是对承担风险的回报，也是生产决策的关键驱动力。它是总收益与总成本之间的差额。
Profit (π) = Total Revenue (TR) - Total Cost (TC)
利润 = 总收益 - 总成本
To evaluate efficiency, firms often use average measures. Average total cost (ATC) is the cost per unit of output:
为了评估效率，企业常使用平均指标。平均总成本 (ATC) 是每单位产出的成本：
ATC = Total Cost ÷ Quantity (Q)
平均总成本 = 总成本 ÷ 数量
Average revenue (AR) is simply the revenue per unit sold, which, under uniform pricing, equals the market price:
平均收益 (AR) 即每单位销售的收入，在统一定价下等于市场价格：
AR = Total Revenue ÷ Q = Price
平均收益 = 总收益 ÷ 数量 = 价格
When ATC is less than AR, the firm earns a profit per unit; when ATC exceeds AR, it makes a loss. These relationships guide production and pricing strategies.
当 ATC 小于 AR 时，企业每单位产品盈利；当 ATC 大于 AR 时，企业亏损。这些关系指导生产与定价策略。
8. Productivity | 生产率
Productivity measures the efficiency with which inputs are converted into outputs. Higher productivity means more output is produced from the same amount of inputs, which can lower costs and raise living standards.
生产率衡量将投入转化为产出的效率。更高的生产率意味着用同样数量的投入生产出更多产出，这能够降低成本并提高生活水平。
Labour productivity, one of the most common measures, is defined as:
劳动生产率是最常见的衡量指标之一，定义为：
Labour Productivity = Total Output ÷ Number of Workers
劳动生产率 = 总产出 ÷ 劳动者数量
Productivity can also be measured in terms of capital or other inputs. Improvements in productivity arise from better technology, more skilled workers, and investment in machinery.
生产率也可以用资本或其他投入来衡量。生产率的提高源于技术进步、劳动力技能提升以及机器设备的投资。
Specialisation and division of labour are key drivers of higher productivity, as they allow workers to focus on tasks where they are most efficient.
专业化和劳动分工是提高生产率的关键驱动力，因为它们使劳动者能够专注于自己最高效的任务。
9. Inflation | 通货膨胀
Inflation is a sustained increase in the general price level of goods and services in an economy over a period of time. It reduces the purchasing power of money, meaning each unit of currency buys fewer goods and services.
通货膨胀是指一个经济体在一段时期内商品和服务总体价格水平的持续上升。它会降低货币的购买力，意味着每一单位货币能购买的商品和服务变少了。
The inflation rate is typically measured using a consumer price index (CPI). The formula is:
通货膨胀率通常用消费者价格指数 (CPI) 来衡量。计算公式为：
Inflation Rate = [(CPI₂ - CPI₁) ÷ CPI₁] × 100%
通货膨胀率 = [(第二年CPI - 第一年CPI) ÷ 第一年CPI] × 100%
Low and stable inflation is generally seen as a sign of a healthy economy, while very high inflation (hyperinflation) can erode savings and damage economic confidence. Deflation, a sustained fall in the price level, can also be harmful.
低且稳定的通货膨胀通常被视为经济健康的标志，而过高的通货膨胀（恶性通胀）会侵蚀储蓄、损害经济信心。通货紧缩，即价格水平的持续下跌，同样可能带来危害。
10. Specialisation and Comparative Advantage | 专业化与比较优势
Specialisation occurs when individuals, firms or countries concentrate on producing a limited range of goods or services. By focusing on what they do best, they can raise productivity and overall output.
专业化发生在个人、企业或国家专注于生产有限种类的商品或服务时。通过专注于自身最擅长的事，他们能够提高生产率和总产出。
Absolute advantage refers to the ability to produce a good using fewer resources than another producer. Comparative advantage, a deeper concept, is the ability to produce a good at a lower opportunity cost than others.
绝对优势是指用比另一个生产者更少的资源生产某种商品的能力。比较优势是一个更深层的概念，指以低于他人的机会成本生产某种商品的能力。
The theory of comparative advantage shows that trade can benefit all parties, even if one party holds an absolute advantage in producing everything. Specialisation according to comparative advantage and then trading allows more efficient worldwide resource use.
比较优势理论表明，即使一方在生产所有东西上都具有绝对优势，贸易仍能使各方受益。依照比较优势进行专业化生产然后进行贸易，可以更有效地利用全球资源。
In Year 8 Economics, you do not need to calculate comparative advantage mathematically, but you should understand that specialisation and trade are built on the idea of differing opportunity costs.
在 Year 8 经济学中，你不需要对比较优势进行数学计算，但应当理解专业化和贸易建立在机会成本差异这一理念之上。
Published by TutorHao | Economics Revision Series | aleveler.com
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