📚 AS WJEC Economics: Core Concepts Review | AS WJEC 经济：核心知识点梳理
Welcome to this comprehensive review of the core topics for AS WJEC Economics. This guide covers the fundamental concepts from both microeconomics and macroeconomics that are essential for success in the examination. By revisiting scarcity, demand and supply, market failure, government intervention, and key macroeconomic principles, you can strengthen your understanding and tackle typical WJEC questions with confidence.
欢迎阅读这篇 AS WJEC 经济核心知识点的全面梳理。本指南涵盖了微观经济学和宏观经济学的核心概念，这些概念对考试成功至关重要。通过回顾稀缺性、需求与供给、市场失灵、政府干预以及关键的宏观经济原理，你可以加深理解，自信地应对 WJEC 的典型试题。
1. The Economic Problem and Scarcity | 经济问题与稀缺性
The fundamental economic problem is scarcity: resources are finite, but human wants are unlimited. This forces economic agents to make choices, leading to opportunity cost — the value of the next best alternative forgone.
基本经济问题是稀缺性：资源是有限的，而人类的欲望是无限的。这迫使经济主体做出选择，从而产生机会成本——即所放弃的次优选择的价值。
The three basic economic questions every society must answer are: 'What to produce?', 'How to produce?', and 'For whom to produce?'. Market, planned, and mixed economies address these questions differently.
每个社会都必须回答三个基本经济问题："生产什么？"、"如何生产？" 以及 "为谁生产？"。市场经济、计划经济和混合经济以不同方式解答这些问题。
2. Factors of Production and Opportunity Cost | 生产要素与机会成本
Resources, or factors of production, are classified into four categories: land (natural resources), labour (human effort), capital (man-made goods used in production), and enterprise (the ability to organise the other factors and bear risk).
资源，或称生产要素，分为四类：土地（自然资源）、劳动力（人类努力）、资本（用于生产的人造物品）和企业（组织其他要素并承担风险的能力）。
Opportunity cost is central to decision-making. For consumers, it may be the forgone enjoyment; for firms, the lost profit from the next best investment; for governments, the value of public goods sacrificed when allocating a budget.
机会成本是决策的核心。对于消费者，可能是放弃的享受；对于企业，是次优投资所丧失的利润；对于政府，是预算分配时所牺牲的公共物品的价值。
3. Production Possibility Frontier (PPF) | 生产可能性边界
A PPF illustrates the maximum possible output combinations of two goods an economy can produce given fixed resources and technology. Points on the curve represent efficient production; points inside indicate underutilisation of resources.
生产可能性边界（PPF）展示了一个经济体在既定资源和技术下所能生产的两种商品的最大产量组合。曲线上的点表示有效率的生产；曲线内的点表示资源未充分利用。
An outward shift of the PPF signifies economic growth, caused by an increase in the quantity or quality of resources, or technological progress. The curve is typically concave to the origin, reflecting increasing opportunity cost as resources are not equally suited to producing all goods.
PPF 向外移动表示经济增长，原因可能是资源数量或质量的提高，或技术进步。曲线通常凹向原点，反映出机会成本递增，因为资源并非同样适用于生产所有商品。
4. Demand and Supply Analysis | 需求与供给分析
Demand is the quantity of a good or service consumers are willing and able to purchase at various prices over a given period. The law of demand states that as price rises, quantity demanded falls, ceteris paribus, due to income and substitution effects.
需求是指在一定时期内，消费者在各种价格水平下愿意并能够购买的商品或服务的数量。需求定律指出，在其他条件不变的情况下，价格上升，需求量下降，原因在于收入效应和替代效应。
Supply reflects the quantity producers are willing and able to sell at different prices. A rise in price usually leads to an expansion of supply, as higher prices increase profitability. Factors shifting the demand curve include changes in income, tastes, prices of related goods, and expectations. Supply shifters include costs of production, technology, taxes, subsidies, and the number of sellers.
供给反映生产者在不同价格下愿意并能够出售的数量。价格上涨通常导致供给量增加，因为更高的价格提高了盈利性。导致需求曲线移动的因素包括收入变化、偏好、相关商品的价格和预期。供给的移动因素包括生产成本、技术、税收、补贴和卖者数量。
5. Elasticity Concepts | 弹性概念
demand (PED) measures the responsiveness of quantity demanded to a change in price. PED = %ΔQd / %ΔP. If |PED| > 1, demand is elastic; if |PED| < 1, it is inelastic; if |PED| ubstitutes, the proportion of income spent, and whether the good is a necessity or luxury.
需求价格弹性（PED）衡量需求量对价格变化的反应程度。PED = %ΔQd / %ΔP。如果 |PED| > 1，需求富有弹性；|PED| < 1，缺乏弹性；|PED| = 1，为单位弹性。决定因素包括替代品的可用性、支出占收入的比例以及商品是必需品还是奢侈品。
Income elasticity of demand (YED) = %ΔQd / % ties 0 < YED < 1, and inferior goods have negative YED. Cross elasticity of demand (XED) = %ΔQd of good A / % ments have negative XED, substitutes have positive XED. Price elasticity of supply (PES) = %ΔQs / %ΔP, influenced by production time, spare capacity, and stock levels.
需求收入弹性（YED）= %ΔQd / %ΔY。正常品 YED 为正，奢侈品 YED > 1，必需品 0 < YED < 1，低档品 YED 为负。交叉弹性（XED）= A 商品需求量变化% / B 商品价格变化%。互补品 XED 为负，替代品 XED 为正。供给价格弹性（PES）= %ΔQs / %ΔP，受生产时间、剩余产能和存货水平影响。
6. Market Equilibrium and Efficiency | 市场均衡与效率
Market equilibrium occurs where quantity demanded equals quantity supplied, establishing an equilibrium price (P₀) and quantity (Q₀). Any price above equilibrium creates a surplus, exerting downward pressure on price; a price below creates a shortage, forcing price upward.
市场均衡出现在需求量等于供给量时，形成均衡价格（P
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