📚 Common Mistakes in A-Level Economics Examinations | A-Level 经济学考试常见错误
Examiners’ reports from Cambridge International A-Level Economics consistently highlight the same avoidable errors: candidates know some theory but lose marks through imprecise terminology, incomplete diagrams, and weak evaluation. This article summarises the most frequent mistakes and how to fix them.
剑桥国际 A-Level 经济学的考官报告反复强调一些本可避免的相同错误：考生掌握了一些理论，却因术语不精确、图表不完整和评估薄弱而丢分。本文总结了最常见的错误及其纠正方法。
1. Confusing Movements Along and Shifts of Demand/Supply Curves | 混淆沿曲线移动与曲线整体平移
Many candidates write “demand increases” when they actually mean quantity demanded increases after a price fall. A movement along the demand curve is caused only by a change in the good’s own price, while a shift of the demand curve is caused by a non-price determinant such as income, tastes, advertising, or the price of substitutes/complements.
许多考生在价格下降后实际想表达 “需求量增加” 时却写成 “需求增加”。沿需求曲线的移动仅由商品自身价格变化引起，而需求曲线的整体平移则由收入、偏好、广告或替代品/互补品价格等非价格因素引起。
Similarly, a change in the price of the good causes a movement along the supply curve, not a shift. Supply shifts arise from changes in costs of production, technology, taxes, subsidies, or the number of firms.
同样，商品自身价格变化引起的是沿供给曲线的移动，而不是供给曲线平移。供给曲线平移源于生产成本、技术、税收、补贴或厂商数量等因素的变化。
Use precise language: say “contraction/extension of demand” or “fall/rise in quantity demanded” for movements, and “increase/decrease in demand” for shifts.
使用精确语言：对于移动，应说 “需求收缩/扩张” 或 “需求量下降/上升”；对于平移，应说 “需求增加/减少”。
2. Incomplete or Unlabelled Diagrams | 图表不完整或未标注
Diagrams are essential in A-Level Economics, but marks are often lost because axes, curves, equilibrium points, and shift directions are not labelled. A diagram without labels is just a drawing, not an economic model.
图表在 A-Level 经济学中至关重要，但考生常因未标注坐标轴、曲线、均衡点和移动方向而失分。没有标注的图表只是图画，而不是经济模型。
Always label price and quantity on the axes, label each curve D, S, SRAS, LRAS, AD, etc., and show the original equilibrium price and quantity. When a curve shifts, draw an arrow and label the new equilibrium clearly.
务必在坐标轴上标注价格和数量，为每条曲线标注 D、S、SRAS、LRAS、AD 等，并标出原均衡价格和数量。当曲线平移时，画出箭头并清楚标出新均衡。
A diagram should be integrated with the text. Refer to it in your explanation: “As shown in the diagram, the rise in costs shifts the supply curve from S to S1, raising price from P to P1.”
图表应与文字结合。在解释中引用图表：”如图所示，成本上升使供给曲线从 S 平移至 S1，价格从 P 上升至 P1。”
3. Vague Definitions and Misused Key Terms | 定义模糊与关键术语误用
Examiners expect precise, syllabus-based definitions. For example, “inflation is a sustained increase in the general price level” is acceptable, but “prices going up” is too vague. Define terms like opportunity cost, scarcity, PED, and externalities accurately.
考官期望基于考纲的准确定义。例如，”通货膨胀是总体价格水平的持续上升” 可以接受，但 “价格上涨” 过于笼统。要准确定义机会成本、稀缺性、需求价格弹性（PED）和外部性等术语。
Do not confuse money, income, and wealth. Money is a medium of exchange and store of value; income is a flow of earnings over time; wealth is a stock of assets at a point in time.
不要混淆货币、收入和财富。货币是交换媒介和价值储藏手段；收入是一段时间内的收入流量；财富是某一时点的资产存量。
Also avoid using “government” when you mean “central bank”. Monetary policy is conducted by the central bank, while fiscal policy is conducted by the government.
还要避免在指 “中央银行” 时使用 “政府”。货币政策由中央银行执行，财政政策由政府执行。
4. Ignoring Ceteris Paribus and Short Run versus Long Run | 忽略其他条件不变与短期/长期区别
Ceteris paribus means “other things being equal”. When explaining a cause-effect relationship, state the assumption. Without ceteris paribus, a price rise may not reduce quantity demanded if incomes are rising at the same time.
“其他条件不变” 是指 “其他因素保持不变”。在解释因果关系时，要说明这一假设。如果没有其他条件不变，当收入同时上升时，价格上涨可能不会减少需求量。
Confusing the short run and long run is another common error. In microeconomics, the short run has at least one fixed factor of production; in the long run all factors are variable. In macroeconomics, the short-run Phillips curve shows a trade-off between inflation and unemployment, but the long-run Phillips curve is vertical.
混淆短期和长期是另一个常见错误。在微观经济学中，短期至少有一种生产要素固定；长期所有要素都可变。在宏观经济学中，短期菲利普斯曲线显示通胀与失业之间存在权衡，但长期菲利普斯曲线是垂直的。
Always specify the time horizon when discussing adjustment. For example, the J-curve effect and the Marshall-Lerner condition apply to the short run versus long run effects of exchange rate changes.
在讨论调整时，务必说明时间范围。例如，J 曲线效应和马歇尔-勒纳条件适用于汇率变化的短期与长期影响。
5. Elasticity Misunderstandings and Calculation Errors | 弹性概念误解与计算错误
Price elasticity of demand (PED) is the percentage change in quantity demanded divided by the percentage change in price: PED = %ΔQd ÷ %ΔP. A common mistake is using absolute changes or inverting the formula.
需求价格弹性（PED）等于需求量变化百分比除以价格变化百分比：PED = %ΔQd ÷ %ΔP。常见错误是使用绝对变化量或将公式颠倒。
Remember that PED has a negative sign, but often quoted in absolute terms. Values less than one are inelastic, greater than one are elastic, and equal to one are unit elastic. Do not confuse elasticity with slope, which depends on units of measurement.
记住 PED 通常为负值，但多数引用其绝对值。小于 1 为缺乏弹性，大于 1 为富有弹性，等于 1 为单位弹性。不要把弹性与斜率混淆，斜率取决于度量单位。
For income elasticity of demand (YED), a positive value indicates a normal good, while a negative value indicates an inferior good. For cross elasticity of demand (XED), a positive value indicates substitutes, and a negative value indicates complements. Many candidates reverse these signs.
对于需求收入弹性（YED），正值表示正常商品，负值表示低档商品。对于需求交叉弹性（XED），正值表示替代品，负值表示互补品。许多考生会颠倒这些符号。
6. Confusing Positive and Normative Statements | 混淆实证表述与规范表述
Positive statements are testable and value-free: “A rise in interest rates is likely to reduce house prices.” Normative statements involve value judgements: “The central bank should raise interest rates.”
实证表述是可检验且不含价值判断的：”利率上升可能降低房价。” 规范表述涉及价值判断：”中央银行应该提高利率。”
In essays, you should mainly use positive analysis to explain and predict. Evaluation can include normative elements only if they are clearly identified as a judgement.
在论文中，应主要使用实证分析来解释和预测。评估可以包含规范要素，但必须明确说明这是价值判断。
Do not present a normative statement as though it were an objective fact. This undermines the analytical quality of your answer.
不要把规范表述当作客观事实来陈述。这会削弱答案的分析质量。
7. Superficial Evaluation and Unsupported Conclusions | 评价肤浅与结论缺乏依据
Cambridge A-Level Economics rewards evaluation that weighs alternatives, considers magnitudes, time lags, and unintended consequences. Simply saying “it depends” is not enough.
剑桥 A-Level 经济学会奖励那些权衡不同选择、考虑影响程度、时滞和意外后果的评估。只说 “视情况而定” 是不够的。
Use evaluative phrases such as “the effectiveness depends on the price elasticity of demand”, “the impact may be limited in the short run”, or “the policy may have unintended supply-side effects”. Support each judgement with economic reasoning.
使用评价性表述，如 “效果取决于需求价格弹性” “短期影响可能有限” 或 “政策可能产生意外的供给侧效应”。每个判断都要有经济学推理支撑。
Conclusions should be consistent with the analysis above. A strong conclusion summarises the main argument and gives a justified final judgement, not a new point or a vague compromise.
结论应与前面的分析一致。有力的结论总结主要论点并给出有依据的最终判断，而不是提出新观点或含糊的折中。
8. Macro Account and Trade Confusions | 宏观账户与贸易概念混淆
Do not confuse the current account, capital account, and financial account of the balance of payments. The current account records trade in goods and services, income flows, and transfers; the financial account records capital flows such as FDI and portfolio investment.
不要混淆国际收支中的经常账户、资本账户和金融账户。经常账户记录商品和服务贸易、收入流动和转移支付；金融账户记录外国直接投资和证券投资等资本流动。
A common error is to argue that a current account deficit is always bad. It may reflect strong domestic demand or a structural lack of competitiveness, and its sustainability depends on how it is financed and the exchange rate regime.
一个常见错误是认为经常账户赤字总是不好的。它可能反映了强劲的国内需求或结构性竞争力不足，其可持续性取决于融资方式和汇率制度。
Similarly, distinguish GDP from GNP. GDP measures output produced within a country’s borders; GNP measures output produced by a country’s residents, regardless of location.
同样，要区分 GDP 与 GNP。GDP 衡量一国境内生产的产出；GNP 衡量一国居民生产的产出，无论地点在哪里。
9. Misreading Inflation, Unemployment and Growth Data | 误读通胀、失业与经济增长数据
Deflation, disinflation,
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