📚 Analyzing Diagrams in the Cambridge International AS & A Level Economics Coursebook | CIE 经济学教材图表分析精要
Mastering diagrammatic analysis is essential for success in CIE AS and A Level Economics. The Cambridge International AS and A Level Economics Coursebook is filled with diagrams that illustrate core concepts, from microeconomic supply and demand to macroeconomic AD-AS models and international trade. This guide breaks down the key diagrams you will encounter, explaining how to interpret, draw, and apply them effectively in examinations.
掌握图表分析是成功应对 CIE AS 和 A Level 经济学考试的关键。剑桥国际 AS 与 A Level 经济学教材中充满了各种图表，从微观层面的供给需求到宏观层面的总需求—总供给模型以及国际贸易，一应俱全。本指南将逐一拆解你会遇到的关键图表，解释如何准确解读、绘制并在考试中灵活运用它们。
1. Demand, Supply and Market Equilibrium | 需求、供给与市场均衡
The demand curve slopes downwards, reflecting the law of demand: as price falls, quantity demanded increases. The supply curve slopes upwards, showing that higher prices incentivise producers to supply more. The intersection determines the equilibrium price and quantity, where there is no tendency for change.
需求曲线向下倾斜，反映了需求定律：价格下降，需求量增加。供给曲线向上倾斜，表明更高的价格会激励生产者供给更多商品。两条曲线的交点决定了均衡价格和均衡数量，此时市场没有自发变动的趋势。
A rightward shift of the demand curve, caused by factors such as rising income for a normal good, creates excess demand at the original price. This pushes the price up until a new equilibrium is reached with higher price and quantity. Conversely, a leftward shift of supply, perhaps due to increased production costs, causes excess demand and a higher price, but a lower quantity.
由于正常品收入上升等因素引起的需求曲线向右移动，会在原价格下造成超额需求。这将推动价格上升，直到达到价格更高、数量也更高的新均衡。相反，供给曲线因生产成本上升等原因向左移动，则会引发超额需求和更高的价格，但均衡数量会下降。
In exam diagrams, always label axes (Price, Quantity), curves (D, S), and the equilibrium point (E). Use arrows to indicate shifts, and show the new equilibrium clearly. Distinguish between a movement along a curve (caused by a change in the good's own price) and a shift of the entire curve (caused by changes in non-price determinants).
在考试绘图中，务必标注坐标轴（价格、数量）、曲线（D、S）以及均衡点（E）。用箭头标示曲线的移动，并清晰绘出新的均衡。要区分沿曲线的移动（由商品自身价格变动引起）和整条曲线的平移（由非价格决定因素变动引起）。
2. Elasticities: Price, Income, Cross and Supply | 弹性：价格弹性、收入弹性、交叉弹性和供给弹性
Price elasticity of demand (PED) measures the responsiveness of quantity demanded to a change in price. A diagram can illustrate perfectly inelastic demand (vertical line), inelastic demand (steep), unit elastic demand, and elastic demand (relatively flat). Perfectly elastic demand is shown as a horizontal line.
需求价格弹性（PED）衡量需求量对价格变动的反应程度。图表可以展示完全无弹性需求（垂直线）、缺乏弹性需求（陡峭）、单位弹性需求以及富有弹性需求（相对平缓）。完全弹性需求则表现为一条水平线。
The slope of the demand curve alone does not indicate elasticity; elasticity varies along a straight-line demand curve. At higher prices, demand is more elastic; at lower prices, it is more inelastic. You may be required to draw a diagram showing how total revenue changes with price changes depending on PED. When demand is inelastic, a price rise increases total revenue; when elastic, a price rise reduces total revenue.
仅凭需求曲线的斜率并不能判断弹性大小；在一条直线型需求曲线上，弹性会随位置变化。价格较高时需求更富有弹性，价格较低时需求更缺乏弹性。你可能需要画出图表来说明总收益如何随价格变动而变化，这取决于 PED。当需求缺乏弹性时，提价会增加总收益；当需求富有弹性时，提价会减少总收益。
Price elasticity of supply (PES) diagrams show the degree to which quantity supplied responds to price changes. A perfectly inelastic supply curve is vertical, while a perfectly elastic supply curve is horizontal. The PES is often linked to the time period: the momentary period is highly inelastic, the short run somewhat more elastic, and the long run even more elastic.
供给价格弹性（PES）图显示了供给量对价格变动的反应程度。完全无弹性供给曲线是垂直的，而完全弹性供给曲线是水平的。PES 往往与时间期限相关：瞬时市场供给高度无弹性，短期供给弹性稍高，长期供给弹性更高。
3. Government Intervention: Price Controls and Taxes | 政府干预：价格管制与税收
A maximum price (price ceiling) set below equilibrium creates a shortage. The diagram shows the horizontal price line below equilibrium, the quantity demanded exceeding quantity supplied, and the welfare loss represented by the reduction in total surplus. Common examples include rent controls and food price caps.
价格上限（最高限价）设定在均衡价格以下会造成短缺。图中会出现一条低于均衡的水平价格线，需求量超过供给量，福利损失表现为总剩余的减少。常见的例子包括租金管制和食品限价。
A minimum price (price floor) set above equilibrium, such as agricultural support prices or minimum wages, results in excess supply. The diagram highlights the surplus quantity and potential government expenditure if the government purchases the surplus. Welfare analysis shows a deadweight loss and possibly a transfer from consumers to producers.
价格下限（最低限价）设定在均衡价格以上，例如农产品支持价格或最低工资，会造成超额供给。图中会突出过剩数量，如果政府收购剩余产品，还会展示潜在的政府支出。福利分析则显示出无谓损失以及消费者向生产者的剩余转移。
Indirect taxes shift the supply curve vertically upwards by the amount of the tax. The diagram can be used to illustrate the tax burden shared between consumers and producers, as well as the tax revenue collected by the government. The more inelastic the demand, the greater the burden on consumers. A subsidy shifts the supply curve downwards, increasing quantity and lowering the price paid by consumers.
间接税会使供给曲线垂直向上移动，幅度为税额。图表可用来展示消费者和生产者分摊的税负，以及政府收取的税收收入。需求越缺乏弹性，消费者承担的税负就越大。补贴则使供给曲线向下移动，增加产量并降低消费者支付的价格。
4. Costs, Revenues and Profit Maximization | 成本、收益与利润最大化
Short-run cost curves include average total cost (ATC), average variable cost (AVC) and marginal cost (MC). The MC curve intersects both ATC and AVC at their minimum points. These U-shaped curves reflect initially increasing and then eventually diminishing returns to the variable factor.
短期成本曲线包括平均总成本（ATC）、平均可变成本（AVC）和边际成本（MC）。MC 曲线分别在 ATC 和 AVC 的最低点与之相交。这些 U 形曲线反映了可变要素起初的收益递增和随后最终的收益递减规律。
A perfectly competitive firm's revenue curves show price, which equals marginal revenue (MR) and average revenue (AR), as a horizontal line at the market-determined price. For a monopolist, the AR curve (demand) slopes downwards, and the MR curve lies below it, falling twice as steeply in a linear case.
完全竞争厂商的收益曲线表现为一条水平线，代表价格，同时也是边际收益（MR）和平均收益（AR），由市场决定。对于垄断厂商，AR 曲线（即需求曲线）向下倾斜，MR 曲线位于其下方，在直线情况下斜率加倍陡峭。
, or loss (AR < ATC). The shut-down point occurs where price falls below AVC; if price covers AVC but not ATC, the firm continues to produce in the short run to minimise losses.
利润最大化产量在 MR = MC 处确定。利用图表可以显示超额利润区域（AR > ATC）、正常利润（AR = ATC）或亏损（AR < ATC）。当价格低于 AVC 时即为停业点；如果价格能覆盖 AVC 但无法覆盖 ATC，厂商在短期内会继续生产以最小化亏损。
5. Perfect Competition and Monopoly | 完全竞争与垄断
In a perfectly competitive market, diagrams show the firm as a price-taker with a horizontal demand curve. In the short run, the firm can earn supernormal profits or incur losses. Entry and exit of firms in the long run drive the price to the minimum of ATC, so only normal profit remains. The market diagram shows industry supply and demand intersecting to determine price, while the firm's diagram takes that price as given.
在完全竞争市场中，图表显示厂商是价格接受者，面临一条水平需求曲线。短期内，厂商可能赚取超额利润，也可能遭受亏损。长期中，厂商的进入和退出将推动价格降至 ATC 的最低点，因此市场中仅剩下正常利润。市场图展示行业供给与需求相交决定价格，而单个厂商图则以该价格为前提。
ges a higher price P on the demand curve. Welfare loss is shown by the area of deadweight loss relative to the competitive outcome. The diagram can also illustrate price discrimination if separate markets are identified.
垄断图表具有向下倾斜的需求（AR）曲线和位于其下方的 MR 曲线。垄断者在 MR = MC 处将产量限制在 Q，并依据需求曲线索要更高的价格 P。与完全竞争结果相比，福利损失表现为无谓损失的区域。该图还可以在区分不同市场时用于说明价格歧视。
Natural monopoly diagrams show a continuously falling ATC curve over the relevant range of output, implying that one large firm can supply the market at a lower cost than multiple firms. This justifies regulation or state ownership in some cases.
自然垄断图表显示在相关产量范围内 ATC 曲线持续下降，这意味着由一家大企业供应市场的成本低于多家企业。这为某些情况下的政府监管或国有化提供了理由。
6. Monopolistic Competition and Oligopoly | 垄断竞争与寡头
In monopolistic competition, the firm's short-run diagram looks similar to a monopoly, with the possibility of supernormal profits. In the long run, entry shifts the firm's demand curve leftwards and makes it more elastic until it is tangent to the ATC curve, eliminating supernormal profits. The result is excess capacity: the firm produces below the minimum efficient scale.
在垄断竞争中，厂商的短期图看起来与垄断相似，存在超额利润的可能。长期中，进入者使厂商的需求曲线向左移动并变得更富有弹性，直至与 ATC 曲线相切，从而消除超额利润。这导致了过剩生产能力：厂商的产量低于最低有效规模。
Oligopoly is often analysed using the kinked demand curve model. The demand curve has a kink at the prevailing price. The upper segment is relatively elastic (competitors do not match price rises), while the lower segment is inelastic (competitors match price cuts). This creates a discontinuous MR curve, helping to explain price rigidity in oligopolistic markets.
寡头市场常用弯折需求曲线模型来分析。需求曲线在现行价格处有一个弯折点。上半部分相对富有弹性（对手不跟着提价），下半部分则缺乏弹性（对手会跟着降价）。这导致 MR 曲线出现不连续的区间，有助于解释寡头市场中的价格粘性。
Game theory payoff matrices (not strictly diagrams, but often required) illustrate interdependence and the incentive to collude or cheat. The prisoner's dilemma explains why firms may not cooperate even when it seems mutually beneficial.
博弈论收益矩阵（尽管不完全是图表，但考试常要求）说明了寡头间的相互依赖以及合谋或欺骗的动机。囚徒困境解释了为什么即使看似对双方都有利，厂商也可能不选择合作。
7. Labour Market | 劳动市场
In a perfectly competitive labour market, the wage rate is determined by the intersection of market demand for labour (derived from marginal revenue product, MRP) and supply of labour. The individual firm faces a perfectly elastic labour supply at the market wage. The firm hires workers up to the point where MRP equals the wage.
在完全竞争的劳动市场中，工资率由市场需求（源自边际收益产品 MRP）与劳动供给的交点决定。单个厂商在既定市场工资下面临完全弹性的劳动供给。厂商雇用工人直至 MRP 等于工资为止。
l cost of labour (MCL) curve above it. It hires where MCL = MRP and pays a wage determined on the ACL curve, which is lower than the competitive wage. The diagram shows fewer workers employed and lower wages, generating exploitation and deadweight loss.
在买方垄断中，存在唯一的劳动购买者。厂商面临向上倾斜的劳动供给（即平均劳动力成本 ACL）曲线，而劳动的边际成本（MCL）曲线位于其上方。它按 MCL = MRP 的条件决定雇用量，并根据 ACL 曲线支付工资，该工资低于完全竞争工资。图表显示就业量更少、工资更低，造成剥削和无谓损失。
Trade union intervention and minimum wages can be shown in labour diagrams. A minimum wage set above the equilibrium in a competitive market creates unemployment; in a monopsony, a carefully set minimum wage can actually increase both employment and wages.
工会干预和最低工资可以用劳动力市场图表示。在竞争性市场中，高于均衡的最低工资会造成失业；而在买方垄断中，一个设置得当的最低工资实际上可以同时增加就业和工资。
8. Aggregate Demand and Aggregate Supply | 总需求与总供给
The AD curve shows the relationship between the price level and real GDP demanded, sloping downwards due to the wealth effect, interest rate effect, and net export effect. The short-run aggregate supply (SRAS) curve slopes upwards because at least one input price (often wages) is sticky. Shifts in AD or SRAS cause changes in real GDP and the price level.
AD 曲线表示价格水平与实际 GDP 需求之间的关系，因财富效应、利率效应和净出口效应而向下倾斜。短期总供给（SRAS）曲线向上倾斜，因为至少有一种要素价格（通常是工资）具有粘性。AD 或 SRAS 的移动会引起实际 GDP 和价格水平的变化。
The long-run aggregate supply (LRAS) curve is vertical, representing the economy's full-employment output, which depends on the quantity and quality of factors of production. A diagram showing AD intersecting both SRAS and LRAS can illustrate an inflationary gap (equilibrium beyond LRAS) or a deflationary gap (equilibrium below LRAS).
长期总供给（LRAS）曲线是一条垂直线，代表经济体的充分就业产出水平，该水平取决于生产要素的数量和质量。一张同时包含 AD、SRAS 和 LRAS 的图表可以说明通胀缺口（均衡点位于 LRAS 右侧）或紧缩缺口（均衡点位于 LRAS 左侧）。
Supply-side policies that increase the productive potential shift the LRAS curve to the right. Demands-side policies shift the AD curve. Effective diagrams can demonstrate the trade-offs between growth, unemployment and inflation.
提升生产潜力的供给侧政策会使 LRAS 曲线向右移动。需求侧政策则会使 AD 曲线移动。有效的图表能够展示经济增长、失业和通胀之间的权衡取舍。
9. Macroeconomic Policy and the Phillips Curve | 宏观经济政策与菲利普斯曲线
The short-run Phillips curve shows an inverse relationship between the rate of unemployment and the rate of wage or price inflation. It can be derived from an AD-AS diagram by showing how a rise in AD reduces unemployment but increases the price level, moving along the short-run Phillips curve.
短期菲利普斯曲线显示了失业率与工资或物价通胀率之间的反向关系。它可以通过 AD-AS 图推导得出：AD 上升会降低失业但抬高价格水平，即沿着短期菲利普斯曲线移动。
In the long run, there is no trade-off. The long-run Phillips curve is vertical at the natural rate of unemployment. Expected inflation shifts the short-run Phillips curve; attempts to keep unemployment below the natural rate only lead to accelerating inflation. Diagrams should clearly distinguish the short-run curve from the long-run vertical line.
长期中不存在这种权衡。长期菲利普斯曲线在自然失业率处是一条垂直线。预期通胀会使短期菲利普斯曲线发生移动；试图将失业率维持在自然率之下只会导致加速通胀。图表应清晰区分短期曲线与长期垂直线。
Stagflation (rising unemployment and rising inflation) can be shown by a rightward shift of the short-run Phillips curve, often caused by supply shocks such as an oil price rise. This links back to the SRAS shifting left in the AD-AS framework.
滞胀（失业上升同时通胀上升）可以通过短期菲利普斯曲线向右移动来表现，通常由石油价格上涨等供给冲击引起。这与 AD-AS 框架中 SRAS 向左移动相对应。
10. International Trade and Protectionism | 国际贸易与保护主义
A comparative advantage diagram uses production possibility frontiers (PPFs) to show how specialisation and trade enable countries to consume beyond their own PPFs. Often a simple diagram with two linear PPFs is enough to illustrate gains from trade.
比较优势图利用生产可能性边界（PPF）来说明专业化和贸易如何使国家能够消费超出其自身 PPF 的组合。通常用一个包含两条线性 PPF 的简单图表就足以展示贸易收益。
For a small open economy, a tariff diagram shows the world supply as perfectly elastic at the world price. A tariff shifts the domestic supply curve that includes imports upwards, raising domestic price, reducing imports, and creating deadweight loss. The areas representing consumer loss, producer gain, government revenue and net welfare loss must be clearly labelled.
对于一个小型开放经济体，关税图将世界供给表示为在世界价格处的一条完全弹性线。关税使国内供给（含进口）曲线向上移动，抬高了国内价格，减少了进口，并造成无谓损失。必须清楚标出消费者损失、生产者获利、政府收入和净福利损失等区域。
An import quota diagram shows a vertical import supply curve beyond the quota amount. The price rises to the level where domestic demand minus domestic supply equals the quota. Quotas can create a worse welfare outcome than tariffs because the quota rent may be captured by foreign exporters rather than the domestic government.
进口配额图在配额数量以上表现为一条垂直的进口供给曲线。价格会上升至国内需求减去国内供给等于配额的水平。配额可能导致比关税更差的福利结果，因为配额租金可能被外国出口商攫取，而非像关税一样成为政府收入。
11. Exchange Rates and Balance of Payments | 汇率与国际收支
A floating exchange rate is determined by demand and supply in the foreign exchange market. The demand for a currency derives from exports and capital inflows, while the supply comes from imports and capital outflows. An increase in demand appreciates the currency; an increase in supply depreciates it.
浮动汇率由外汇市场的需求和供给决定。对一国货币的需求源于其出口和资本流入，而供给则来自进口和资本流出。需求增加会使货币升值，供给增加会使货币贬值。
Changes in the exchange rate can be used to correct a current account deficit. A depreciation makes exports cheaper and imports dearer, thereby improving net exports. However, the J-curve effect diagram shows that in the short run, the trade balance may worsen before it improves because of existing contracts and inelastic short-run demand.
汇率变动可用于纠正经常账户逆差。贬值会使出口更便宜、进口更昂贵，进而改善净出口。然而，J 曲线效应图显示，由于现有合同和短期需求缺乏弹性，贸易收支在短期中可能会先恶化，然后才会改善。
A fixed exchange rate diagram shows a central bank intervening to buy or sell its own currency to maintain the peg. If the equilibrium exchange rate is below the fixed rate, the central bank must sell foreign reserves to buy domestic currency, shifting the demand curve to the right, and vice versa.
固定汇率图显示央行通过买卖本币来维持钉住汇率。如果均衡汇率低于固定汇率，央行必须出售外汇储备以购买本币，从而使需求曲线向右移动，反之亦然。
12. Income Inequality and the Lorenz Curve | 收入不平等与洛伦兹曲线
The Lorenz curve plots the cumulative percentage of income against the cumulative percentage of the population. A perfectly equal distribution would be a 45-degree line. The further the Lorenz curve bows below the line of equality, the greater the inequality. The Gini coefficient is the ratio of the area between the line of equality and the Lorenz curve to the entire area under the equality line.
洛伦兹曲线描绘了累计收入百分比与累计人口百分比之间的关系。完全平等的分配将是一条 45 度线。洛伦兹曲线越偏离平等线，不平等程度就越高。基尼系数就是平等线与洛伦兹曲线之间的面积除以平等线下方总面积所得的比率。
Shifts in the Lorenz curve over time or between countries can illustrate changes in inequality. Reasons for shifts include changes in taxation, welfare benefits, education, and the minimum wage. A diagram can also incorporate the role of redistribution by showing pre-tax and post-tax Lorenz curves.
洛伦兹曲线随时间或在不同国家之间发生的移动可以反映不平等程度的变化。移动的原因包括税收、福利、教育和最低工资的变化。该图还可以引入再分配的角色，通过显示税前和税后的洛伦兹曲线加以说明。
The Kuznets curve hypothesises a relationship between economic development and inequality, with inequality first rising and then falling as GDP per capita increases. Though not always empirically robust, the inverted-U shape diagram is useful for discussing structural change and policy.
库兹涅茨曲线提出了一个经济发展与不平等关系的假说：随着人均 GDP 的增长，不平等程度先上升后下降，呈倒 U 形。尽管该假说在实证上并非总是成立，但这张倒 U 形图对于讨论结构变迁和政策很有帮助。
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