📚 IB & OCR Economics: Typical Example Questions Explained | IB OCR 经济：典型例题详解
Mastering economics exam technique requires more than memorising definitions — it demands the ability to apply concepts to unfamiliar scenarios and to structure answers logically. Whether you are preparing for IB or OCR assessments, worked examples are an excellent way to sharpen your analytical skills. This article walks you through ten typical questions drawn from microeconomics and macroeconomics, demonstrating how to break down prompts, use diagrams, perform calculations, and build evaluative commentary. Each example is designed to reflect the common command terms seen in both qualifications, such as ‘explain’, ‘calculate’, ‘analyse’ and ‘evaluate’.
掌握经济学考试技巧不只是背诵定义，更要求能够将概念应用于陌生情境并有条理地组织答案。不论你备考的是IB还是OCR，例题精解都是提升分析能力的绝佳途径。本文精选微观与宏观共十道典型题目，一步步展示如何拆解设问、运用图形、进行运算并撰写评价性评论。每道例题都贴合两大考试中常见的指令词，如“解释”、“计算”、“分析”与“评价”。
1. Demand and Supply Shifts | 需求与供给的移动
Question: The market for electric scooters has experienced a simultaneous increase in consumer incomes and a fall in the cost of lithium batteries. Explain the possible effects on equilibrium price and quantity.
题目：电动滑板车市场同时经历了消费者收入上升和锂电池成本下降。解释这对均衡价格与数量的可能影响。
Begin by identifying that electric scooters are likely normal goods, so higher income shifts demand to the right. Lower battery costs reduce production expenses, shifting supply to the right as well.
首先确认电动滑板车很可能是正常品，收入上升会使需求曲线向右移动。电池成本降低使生产费用下降，供给曲线也向右移动。
Draw a diagram with both demand and supply shifting right. The new equilibrium quantity will unambiguously increase, but the price change depends on the relative magnitudes of the shifts.
绘出需求与供给同时右移的图形。新的均衡数量必定增加，但价格变化取决于两条曲线移动的相对幅度。
If demand shifts more than supply, price rises; if supply shifts more, price falls. If they shift by the same amount, price remains constant. Conclude by noting that without knowing the exact elasticities and shift sizes, the price outcome is indeterminate, yet quantity rises.
如果需求移动幅度大于供给，价格上升；如果供给移动更大，价格下降；若移动幅度相同，价格不变。最后指出，在不知道具体弹性和移动大小的情况下，价格结果不确定，但数量一定上升。
2. Price Elasticity of Demand Calculation | 需求价格弹性计算
Question: When the price of a cinema ticket rises from £10 to £12, quantity demanded falls from 500 tickets per day to 400. Calculate PED and interpret the result.
题目：电影票价格从£10升至£12时，日需求量从500张降至400张。计算PED并解读。
Use the midpoint formula for accuracy:
PED = [ (Q₂ – Q₁) / ((Q₁+Q₂)/2) ] ÷ [ (P₂ – P₁) / ((P₁+P₂)/2) ]
采用中点公式以保证准确性：
PED = [ (Q₂ – Q₁) / ((Q₁+Q₂)/2) ] ÷ [ (P₂ – P₁) / ((P₁+P₂)/2) ]
Change in quantity = 400 – 500 = -100; average quantity = (500+400)/2 = 450. Change in price = £12 – £10 = £2; average price = (£10+£12)/2 = £11.
数量变化=400-500=-100；平均数量=(500+400)/2=450。价格变化= £12-£10=£2；平均价格=(£10+£12)/2=£11。
So %ΔQd = (-100/450)×100 ≈ -22.22%; %ΔP = (2/11)×100 ≈ 18.18%. PED = -22.22 / 18.18 ≈ -1.22 (in absolute terms, 1.22).
因此 %ΔQd = (-100/450)×100 ≈ -22.22%；%ΔP = (2/11)×100 ≈ 18.18%。PED = -22.22 / 18.18 ≈ -1.22（绝对值1.22）。
Interpretation: since |PED| > 1, demand is price elastic. The cinema’s total revenue will fall because the proportionate drop in quantity demanded outweighs the proportionate price rise.
解读：因|PED|>1，需求富有弹性。影院的收入将下降，因为需求量的下降幅度超过了价格上升幅度。
3. Maximum Price Control | 最高限价
Question: The government imposes a maximum price (ceiling) on rented accommodation below the free-market equilibrium. Analyse the market consequences.
题目：政府对租房市场设定低于自由市场均衡的最高限价。分析市场后果。
A binding ceiling set below equilibrium creates a shortage: quantity demanded exceeds quantity supplied at that price.
低于均衡的有约束力限价会造成短缺：在该价格下需求量超过供给量。
Graphically, the horizontal price line cuts the demand curve at a point further right than the supply curve. The vertical distance between Qd and Qs is the excess demand.
图形上，水平限价线与需求曲线的交点比供给曲线交点位置更靠右。Qd与Qs的垂直距离即为超额需求。
Consequences include black markets, reduced quality, longer waiting lists, and allocative inefficiency. Landlords may exit the market, further compressing supply. However, equity for low-income tenants improves.
后果包括黑市、质量下降、等待名单加长与配置效率缺失。房东可能退出市场，进一步压缩供给。但对低收入租户的公平性有所改善。
Evaluate by noting that the magnitude of the shortage depends on the elasticities of demand and supply. If supply is inelastic, shortage is smaller, but quality deterioration may be worse.
评价时指出短缺程度取决于供需弹性。若供给缺乏弹性，短缺较小，但质量恶化可能更严重。
4. Indirect Tax and Incidence | 间接税与税负归宿
Question: A specific tax of £3 per unit is levied on sugar-sweetened beverages. Using a diagram, explain how the tax burden is shared between consumers and producers.
题目：对含糖饮料征收每单位£3的从量税。用图形解释税负如何在消费者与生产者之间分摊。
A specific tax shifts the supply curve vertically upwards by £3. The new equilibrium price paid by consumers (Pc) is higher than the pre-tax equilibrium, while the price received by producers (Pp) is Pc minus £3.
从量税使供给曲线垂直上移£3。消费者支付的新均衡价格(Pc)高于税前均衡，而生产者实际收到的价格(Pp)为Pc减去£3。
Consumer incidence = Pc – P*, producer incidence = P* – Pp. The more inelastic the demand relative to supply, the greater the consumer share.
消费者负担 = Pc – P*，生产者负担 = P* – Pp。需求相对于供给越缺乏弹性，消费者承担的份额越大。
In this market, add a diagram with relatively elastic demand; producer incidence is larger. Discuss how tax revenue is represented by the shaded rectangle. The deadweight loss triangle illustrates net welfare reduction.
在本市场中，假设需求较有弹性，生产者负担更大。讨论税收收入由阴影矩形表示。无谓损失三角形体现了净福利下降。
5. Subsidy and Welfare Effects | 补贴与福利效应
Question: Analyse the impact of a per-unit subsidy to producers of solar panels on consumer surplus, producer surplus, and government cost.
题目：分析对太阳能板生产者的单位补贴对消费者剩余、生产者剩余和政府支出的影响。
A subsidy shifts the supply curve down vertically by the subsidy amount. The new equilibrium price falls from P* to Pc (consumers pay less), while the producer price rises to Pp = Pc + subsidy.
补贴使供给曲线垂直下移补贴金额。新均衡价格由P*降至Pc（消费者支付更少），而生产者价格上升至Pp=Pc+补贴。
Consumer surplus increases because of the lower price and higher quantity. Producer surplus rises as they receive a higher effective price on more units.
消费者剩余因价格下降和数量上升而增加。生产者剩余增加，因为他们对更多数量获得更高的有效价格。
The government cost equals the subsidy per unit multiplied by the new equilibrium quantity. The area overshadows a deadweight loss where marginal social cost exceeds marginal social benefit beyond the efficient output.
政府支出为每单位补贴乘以新均衡数量。该面积中有一部分属于无谓损失，因为超出有效产出后边际社会成本超过边际社会收益。
Evaluation: if the subsidy encourages positive externalities (e.g., reduced carbon emissions), the welfare gain may offset the deadweight loss. However, opportunity cost of public funds must be weighed.
评价：若补贴激励了正外部性（如减少碳排放），福利收益可能抵消无谓损失。但必须权衡公共资金的机会成本。
6. Profit Maximisation and Shut-down Point | 利润最大化与停业点
Question: A firm in a perfectly competitive market faces a market price of £25. Its total cost function is TC = 100 + 2q + 0.1q². Determine the profit-maximising output and assess whether the firm should continue production.
题目：完全竞争市场中的一家企业面临市场价格£25。总成本函数为TC=100+2q+0.1q²。求利润最大化产出，并判断企业应否继续生产。
In perfect competition, P = MR. So MR = £25. Marginal cost (MC) is the derivative of TC: MC = 2 + 0.2q.
完全竞争下P=MR，故MR=£25。边际成本(MC)是TC的导数：MC = 2 + 0.2q。
Set MR = MC: 25 = 2 + 0.2q → 0.2q = 23 → q = 115 units.
令MR=MC：25 = 2 + 0.2q → 0.2q = 23 → q=115单位。
Profit = TR – TC = 25×115 – [100 + 2(115) + 0.1(115²)] = 2875 – (100+230+1322.5) = 2875 – 1652.5 = £1222.5 profit. So firm is profitable.
利润 = TR – TC = 25×115 – [100+2(115)+0.1(115²)] = 2875 – (100+230+1322.5) = 2875 – 1652.5 = £1222.5利润。企业盈利。
Even if loss-making, the firm should continue if P > AVC. AVC = (2q + 0.1q²)/q = 2 + 0.1q. At q=115, AVC = 2+11.5=13.5, far below P=25, so definitely continue.
即使亏损，只要P>AVC，企业也应继续生产。AVC=(2q+0.1q²)/q=2+0.1q。在q=115时，AVC=13.5，远低于£25，故肯定继续。
7. Oligopoly Kinked Demand Curve | 寡头弯折需求曲线
Question: Explain the kinked demand curve model and its implication for price rigidity in oligopolistic markets.
题目：解释弯折需求曲线模型及其对寡头市场价格刚性的含义。
The model assumes that if a firm raises its price, rivals will not follow, causing a large loss of market share. If it cuts its price, rivals will match to protect sales.
该模型假设：若一家企业提价，对手不会跟进，导致市场份额大幅丧失；若降价，对手会跟随以保卫销量。
This creates a demand curve that is relatively elastic above the current price and relatively inelastic below it, hence the kink at the prevailing price.
这导致需求曲线在当前价格上方相对富有弹性，下方相对缺乏弹性，因而在现行价格处形成弯折。
The marginal revenue curve has a vertical discontinuity exactly below the kink. Even if marginal cost changes within that gap, the firm’s profit-maximising price and output stay unchanged, explaining price stickiness.
边际收益曲线在弯折正下方出现垂直断裂。只要边际成本在该断裂区间内变化，企业的最优价格与产出保持不变，这就解释了价格粘性。
Criticism: the model does not explain how the initial price is determined; it only addresses non-price competition such as advertising and branding.
局限：模型未解释初始价格如何形成，只突出了广告与品牌等非价格竞争的重要性。
8. The Multiplier Effect | 乘数效应
Question: In a closed economy, the marginal propensity to consume (MPC) is 0.8. Calculate the simple multiplier. If the government increases spending by £50 million, what is the total increase in national income?
题目：封闭经济中，边际消费倾向(MPC)为0.8。计算简单乘数。若政府支出增加£5000万，国民收入总共增加多少？
The multiplier k = 1 / (1 – MPC) = 1 / (1 – 0.8) = 1/0.2 = 5. Alternatively, k = 1 / MPS, where MPS = 0.2, giving the same result.
乘数 k = 1/(1-MPC) = 1/(1-0.8) = 1/0.2 = 5。亦可用k=1/MPS，MPS=0.2，结果相同。
Total increase in national income ΔY = k × ΔG = 5 × £50 million = £250 million.
国民收入总增加 ΔY = k × ΔG = 5 × £5000万 = £2.5亿。
Explain the process: initial spending creates income for households, who spend 80% of it, generating further income and consumption rounds until the total reaches five times the injection.
解释过程：初始支出为家庭创造收入，他们消费其中80%，进而引发更多收入与消费轮次，直至总收入达到初始注入的五倍。
Evaluation: the simple multiplier assumes idle capacity. In reality, crowding out, imports, and taxes lower the value. The actual multiplier may be closer to 1.5-2 in an open economy.
评价：简单乘数假设存在闲置产能。现实中挤出效应、进口和税收会使乘数变小。在开放经济中实际乘数可能仅为1.5-2。
9. Comparative Advantage and Terms of Trade | 比较优势与贸易条件
Question: Country X can produce 20 units of wheat or 10 units of wine per hour. Country Y can produce 15 wheat or 30 wine. Determine who has comparative advantage in each good and suggest a mutually beneficial terms of trade.
题目：X国每小时可生产20单位小麦或10单位葡萄酒。Y国每小时可生产15小麦或30葡萄酒。判断各国的比较优势，并提出互利的贸易条件。
| Country | Wheat/hour | Wine/hour |
|---|---|---|
| X | 20W | 10Wi |
| Y | 15W | 30Wi |
Opportunity cost of 1 wheat: for X = 10/20 = 0.5 wine; for Y = 30/15 = 2 wine. So X has lower opportunity cost in wheat → comparative advantage in wheat. Y has comparative advantage in wine (opportunity cost of 1 wine in X: 2 wheat, in Y: 0.5 wheat).
1单位小麦的机会成本：X国=10/20=0.5葡萄酒；Y国=30/15=2葡萄酒。故X国在小麦上机会成本更低→比较优势在小麦。Y国在葡萄酒上具有比较优势（葡萄酒的机会成本：X国2小麦，Y国0.5小麦）。
Terms of trade for 1 wheat must lie between 0.5 wine (X’s cost) and 2 wine (Y’s cost), e.g., 1 wheat for 1 wine. Both would gain from trade.
贸易条件中1单位小麦交换的葡萄酒须介于0.5（X国成本）和2（Y国成本）之间，例如1小麦换1葡萄酒。两国均可从贸易中获利。
10. Monetary Policy Transmission Mechanism | 货币政策传导机制
Question: Explain how a central bank’s decision to lower the policy interest rate is transmitted to aggregate demand and inflation.
题目：解释央行下调政策利率如何传导至总需求与通胀。
A lower policy rate reduces commercial banks’ borrowing costs, so they reduce interest rates on loans and mortgages. This encourages consumption (C) and investment (I).
政策利率下降降低商业银行借贷成本，它们进而调低贷款利率与按揭利率，刺激消费(C)和投资(I)。
Lower interest rates also reduce the reward for saving, disincentivising saving and boosting spending. Asset prices such as shares and houses may rise, creating a positive wealth effect.
低利率还降低了储蓄回报，抑制储蓄又刺激支出。股价与房价可能上涨，产生正财富效应。
In an open economy, lower rates can lead to a depreciation of the currency, boosting net exports (X-M). The overall AD increases, shifting AD to the right.
在开放经济中，利率下降会导致本币贬值，促进净出口(X-M)。总需求上升，AD曲线右移。
If the economy is near full capacity, higher AD may cause demand-pull inflation. The strength of transmission depends on confidence, bank lending willingness, and time lags.
若经济接近充分产能，总需求上升可能引发需求拉上型通胀。传导强度取决于信心、银行放贷意愿和时滞。
Evaluation: during a liquidity trap, even zero interest rates may fail to stimulate AD because consumers and firms prefer to hold cash. Quantitative easing might then be used as an unconventional tool.
评价：在流动性陷阱中，即使零利率也难以刺激总需求，因为消费者和厂商宁愿持有现金。此时可能动用量化宽松等非常规工具。
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