ALEVEL经济需求与供给均衡变化重难点汇总，犀牛教育Alevel培训课程抢位中
发布于：2026-06-30 16:43 阅读次数：次 编辑：董嘉瑞
需求与供给均衡变化真题精讲
CAIE 算数值、Edexcel 画箭头、AQA 读表格、OCR 讲过程——四大考局同一知识点，四种打开方式
总览：各考局近 3 年考查频率与风格
CAIE
题目 1：选择题 —— 同时变化比较
英文原题 (CAIE 9708/12/M/J/23 adapted)
The diagram shows the demand and supply curves for a good. There is an increase in demand and a decrease in supply. The increase in demand is larger in magnitude than the decrease in supply. What will happen to the equilibrium price and quantity?
中文翻译
下图显示了某种商品的需求曲线和供给曲线。需求增加，供给减少。需求增加的幅度大于供给减少的幅度。均衡价格和均衡数量会发生什么变化？
英文解答
Demand increase → price ↑, quantity ↑; Supply decrease → price ↑, quantity ↓. Net effect on price: both push price up → price definitely increases. Net effect on quantity: demand pushes up, supply pushes down. Since demand increase > supply decrease (in magnitude), the quantity increases. Correct answer: A
中文点评
关键点：分别分析需求变化和供给变化对价格和数量的独立影响，再合成。常见错误：忘记比较幅度，直接选“不确定”或“数量减少”。考官报告指出，CAIE学生常混淆“需求增加幅度大于供给减少幅度”的含义。
题目 2：数据回应题 —— 计算新均衡
英文原题 (CAIE 9708/22/O/N/22 adapted)
The demand and supply functions for a product are: Qd = 120 - 3P, Qs = 20 + 2P, where P is price in dollars.
(a) Calculate the equilibrium price and quantity. (b) Suppose the government provides a subsidy of $5 per unit to producers. Derive the new supply function and calculate the new equilibrium price and quantity. (c) Calculate the total cost of the subsidy to the government.
中文翻译
某产品的需求函数和供给函数为：Qd = 120 - 3P，Qs = 20 + 2P，其中 P 单位为美元。(a) 计算均衡价格和均衡数量。(b) 假设政府向生产者提供每单位 5 美元的补贴。推导新的供给函数，并计算新的均衡价格和数量。(c) 计算政府补贴的总支出。
英文解答
(a) Set Qd = Qs: 120 - 3P = 20 + 2P → 100 = 5P → P = 20. Substitute: Q = 120 - 3×20 = 60. Equilibrium: P=$20, Q=60.
(b) Subsidy to producer → new supply: Qs = 20 + 2(P+5) = 30 + 2P. Set equal to demand: 120 - 3P = 30 + 2P → 90 = 5P → P = 18 (price paid by consumers). Producer receives P+5 = 23. New quantity: Q = 120 - 3×18 = 66.
(c) Government cost = subsidy per unit × new quantity = 5 × 66 = $330.
中文点评
计算步骤：补贴给生产者时，新供给函数为 Qs = 原函数中 P 换成 (P + 补贴额)。常见错误：误将补贴加入需求函数。CAIE 要求写出完整推导步骤。考局差异：Edexcel 类似题会要求“用图像表示补贴的福利效果”。
Edexcel
题目 1：选择题 —— 画图判断移动方向
英文原题 (Edexcel IAL Unit 1 Jan 2023 adapted)
Which of the following would cause the supply curve for fresh salmon to shift to the left?
A. A rise in the price of fish feed (a major cost for salmon farms)
B. A fall in the price of frozen salmon (a substitute in production)
C. A government subsidy to salmon farmers
D. An improvement in fishing technology
中文翻译
以下哪一项会导致新鲜三文鱼的供给曲线左移？A. 鱼饲料价格上涨 B. 冷冻三文鱼（生产上的替代品）价格下降 C. 政府向三文鱼养殖户提供补贴 D. 捕捞技术改进
英文解答
Supply curve left = decrease in supply. A: Higher input cost → supply decreases → left shift. B: Fall in price of substitute in production makes producing fresh salmon more attractive → supply increases (right shift). C: Subsidy → right shift. D: Technology → right shift. Correct answer: A
中文点评
关键点：供给曲线左移 = 供给减少。Edexcel 特色：这类题目往往要求考生在草稿纸上画出原始供给曲线，用箭头标出移动方向。常见错误：混淆“生产上的替代品”与“消费上的替代品”。
题目 2：数据分析 + 画图题
英文原题 (Edexcel IAL Unit 1 Oct 2022 Data Response adapted)
Table 1 shows the demand and supply schedule for coffee in a country. (a) What is the equilibrium price and quantity? (b) On a diagram, draw the demand and supply curves. Label the equilibrium point E. (c) Suppose a successful advertising campaign increases demand for coffee by 30 kg at each price. Show the new demand curve and label the new equilibrium E₁. Explain the effect on price and quantity.
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中文翻译
表1显示了某国咖啡的需求和供给表。(a) 均衡价格和均衡数量是多少？(b) 在图表上绘制需求曲线和供给曲线，标出均衡点 E。(c) 假设一次成功的广告宣传活动使咖啡在每个价格下的需求增加 30 公斤。在同一个图上画出新的需求曲线，标出新均衡点 E₁，解释对价格和数量的影响。
英文解答
(a) Equilibrium where Qd = Qs: at P=$3.00, Qd=80, Qs=80 → P=$3.00, Q=80 kg.
(b) Diagram: axes labeled, points plotted, downward demand, upward supply, intersection at E(80, 3.00).
(c) New demand: add 30 to each Qd. New schedule: at P=3.00→110, P=3.50→90, etc. New equilibrium between P=3.00 and 3.50, approx P=$3.25, Q≈95 kg. Effect: price rises from $3.00 to $3.25, quantity rises from 80 to 95 kg.
中文点评
作图要求：Edexcel 要求手绘图必须清晰标注坐标轴、曲线名称、初始均衡 E、新均衡 E₁，并用箭头标明需求曲线移动方向。常见错误：只写结论不引用数据。
AQA
题目 1：数据表题 —— 判断变化类型
英文原题 (AQA AS Economics Paper 1 May 2023 adapted)
Table A shows price and quantity data for a product over two years. Which of the following best explains the changes from Year 1 to Year 2? A. An increase in demand only B. An increase in supply only C. A decrease in supply only D. An increase in demand and a decrease in supply
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中文翻译
表 A 显示了某产品两年的价格和数量数据。哪一项最能解释从第 1 年到第 2 年的变化？A. 仅需求增加 B. 仅供给增加 C. 仅供给减少 D. 需求增加且供给减少
英文解答
Year 1 equilibrium (10,500). Year 2 at price 12, Qs=400, actual quantity traded is 400 (supply-constrained). Price rose, quantity fell. Only supply decrease can cause price rise and quantity fall. Correct answer: C
中文点评
AQA 特色：常给出非均衡数据，要求学生识别哪条曲线发生了移动。技巧：比较同一价格下的数量变化。常见错误：被第 2 年的高需求量（600）迷惑，误以为需求也增加了。
题目 2：短论述 —— 从表格到图像
英文原题 (AQA AS Economics Paper 2 June 2022 adapted)
The table shows the demand schedule for apples. (a) Plot the demand curve. (b) Supply is perfectly inelastic at 160 kg. Draw supply and find equilibrium price. (c) A new study increases demand by 20% at each price. Calculate the new equilibrium price and quantity.
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中文翻译
下表显示了苹果的需求表。(a) 绘制需求曲线。(b) 供给完全无弹性为 160 公斤，画出供给曲线并求均衡价格。(c) 新研究表明苹果极其健康，每个价格下的需求增加 20%，计算新的均衡价格和数量。
英文解答
(a) Plot points, downward demand.
(b) Supply vertical at Q=160 → equilibrium at P=70 pence, Q=160.
(c) New Qd = 1.2×(original). Original demand linear: Qd = 300 - 2P. New Qd = 360 - 2.4P. Set =160 → 360-2.4P=160 → P≈83.33 pence, Q=160 kg.
中文点评
计算注意：20% 增加是指每个价格下的需求量乘以 1.2，而不是在原均衡数量上加 20%。AQA 评分要求精确计算具体价格。
OCR
题目 1：情景分析 —— 动态调整过程
英文原题 (OCR A Level Economics Component 1 Jan 2023 adapted)
Explain the process by which the market for a good returns to equilibrium following an increase in demand. In your answer, refer to excess demand and the price mechanism.
中文翻译
解释某商品需求增加后，市场如何通过价格机制恢复均衡。在回答中提及“超额需求”和“价格机制”。
英文解答（结构化）
Initial equilibrium. Demand increase shifts D right → at original price, excess demand (shortage). Price mechanism: shortage puts upward pressure on price. Price rises, causing contraction of Qd and extension of Qs. Process continues until excess demand eliminated. New equilibrium at higher P and Q.
中文点评
OCR 偏好：必须使用“excess demand”“excess supply”术语，并描述价格变动的动态过程。常见错误：只写结果，不写中间过程。
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