📚 IGCSE AQA Economics: Demand and Supply | IGCSE AQA 经济：需求与供给 考点精讲
In IGCSE Economics, the principles of demand and supply form the cornerstone of market analysis. Understanding how buyers and sellers interact to determine prices and quantities is essential for explaining real-world economic events. This article breaks down key concepts, diagrams, and exam tips according to the AQA syllabus.
在 IGCSE 经济学中，需求与供给原理是市场分析的基石。理解买卖双方如何相互作用决定价格和数量，对于解释现实经济事件至关重要。本文根据 AQA 考纲，详细梳理了核心概念、图解与考试技巧。
1. Understanding Demand and Effective Demand | 理解需求与有效需求
In economics, demand is not simply a desire for a product; it must be backed by the ability to pay. Effective demand refers to the quantity of a good or service that consumers are willing and able to purchase at various prices over a given period, ceteris paribus.
在经济学中，需求不仅仅是对商品的渴望；它必须由支付能力支撑。有效需求是指在其他条件不变的情况下，消费者在一定时期内愿意并且能够购买的商品或服务的数量。
A demand schedule shows the relationship between price and quantity demanded in a table, while a demand curve plots this relationship on a graph. The demand curve normally slopes downwards from left to right, indicating an inverse relationship between price and quantity demanded.
需求表通过表格展示价格与需求量之间的关系，而需求曲线则在图形上绘制这种关系。需求曲线通常从左向右下方倾斜，表明价格与需求量之间存在反比关系。
2. The Law of Demand | 需求定律
The law of demand states that, ceteris paribus, as the price of a product falls, the quantity demanded rises, and as the price rises, the quantity demanded falls. This occurs because of two main effects: the income effect and the substitution effect.
需求定律指出，在其他条件不变的情况下，商品价格下降时，需求量上升；价格上升时，需求量下降。这源于两种主要效应：收入效应和替代效应。
The income effect: a lower price increases consumers’ real income, allowing them to purchase more of the good. The substitution effect: consumers switch from relatively more expensive alternatives to the now cheaper product.
收入效应：价格降低增加了消费者的实际收入，使他们能够购买更多该商品。替代效应：消费者从相对更贵的替代品转向现在更便宜的商品。
3. Movements Along the Demand Curve vs Shifts | 沿需求曲线的移动与需求曲线的平移
A movement along the demand curve occurs solely due to a change in the price of the good itself. For example, if the price decreases from P1 to P2, the quantity demanded increases from Q1 to Q2, resulting in a downward movement along the same curve. This is called an extension of demand. Conversely, a price increase leads to a contraction of demand.
沿需求曲线的移动仅由商品自身价格变化引起。例如，如果价格从 P1 下降到 P2，需求量从 Q1 增加到 Q2，导致在同一条曲线上向下移动，这称为需求量的增加（extension）。相反，价格上升导致需求量的减少（contraction）。
A shift of the entire demand curve happens when any non-price factor changes. If demand increases, the curve shifts to the right (from D1 to D2); if demand decreases, it shifts to the left. At every possible price, a different quantity is demanded.
当任何非价格因素变化时，整个需求曲线会发生平移。如果需求增加，曲线向右移动（从 D1 到 D2）；如果需求减少，则向左移动。在每个可能的价格水平上，需求量都不一样。
4. Factors Causing Shifts in Demand | 导致需求平移的因素
Several factors can shift the demand curve. It is vital to remember these for exam analysis. Use the acronym PASIFIC to recall them: Population, Advertising, Substitutes’ prices, Income, Fashion/tastes, Interest rates (for credit-based goods), Complements’ prices.
许多因素会导致需求曲线平移，记住它们对考试分析至关重要。可以使用首字母缩写 PASIFIC 来记忆：人口、广告、替代品价格、收入、时尚/偏好、利率（对于依赖信用的商品）、互补品价格。
| Factor (English) | 因素（中文） | Effect on Demand | 对需求的影响 |
|---|---|---|---|
| Income (normal good) | 收入（正常商品） | Increase in income → demand rises | 收入增加 → 需求上升 |
| Income (inferior good) | 收入（低档商品） | Increase in income → demand falls | 收入增加 → 需求下降 |
| Price of substitutes | 替代品价格 | If substitute price rises, demand for the good rises | 如果替代品价格上升，对该商品需求上升 |
| Price of complements | 互补品价格 | If complement price rises, demand falls | 如果互补品价格上升，需求下降 |
| Tastes and preferences | 偏好与品味 | Favourable change increases demand | 更多咨询请联系16621398022（同微信）
CommentsMore posts |
屏轩国际教育cambridge primary/secondary checkpoint, cat4, ukiset,ukcat,igcse,alevel,PAT,STEP,MAT, ibdp,ap,ssat,sat,sat2课程辅导，国外大学本科硕士研究生博士课程论文辅导