Economics HKDSE Knowledge Library

全英文对标 HKEAA 官方课纲。每个术语给出【官方英文定义 + 中文注解】。定义题必须一字不差背诵英文原文。

考試結構（2025 官方 Public Assessment）

Paper	Section	題型	比重	時長	範圍
Paper 1	—	45 題 MC（必答）	30%	60 分鐘	Compulsory Part
Paper 2	A	9 題 Short Q（必答）	26%（44 分）	2 小時 30 分	Compulsory Part
	B	Structured / Essay（含 1 題 DRQ，必答）	35%（60 分）		Compulsory Part
	C	Elective Part（2 選 1）	9%（16 分）		Elective Part

2024 因特殊安排 Paper 2 取消 C 部、Section A 50 分 / B 70 分；2025 起恢復正常結構。Paper 1 平均分約 57–64%（即 45 題對 26–29 題），MC 是性價比最高的 30 分。

Compulsory Part 課程架構（A–J，溫習優先級）

微觀 Micro	宏觀 Macro
A Basic Economic Concepts	F Measurement of Economic Performance
B Firms and Production	G National Income Determination & Price Level
C Market and Price	H Money and Banking
D Competition & Market Structure	I Macroeconomic Problems & Policies
E Efficiency, Equity & Role of Government	J International Trade & Finance

Paper 1 MCQ 各課題命中率（2017–2024 平均，決定溫習先後）

課題	平均題數 / 卷	備註
B Firms and Production	7–8	年年必出大戶
C Market and Price	7–10	供需圖是靈魂
H Money and Banking	4–6	存款創造必考
I Macro Problems & Policies	7–9	政策分析重災區
J International Trade	4–6	比較優勢年年見
A / E / F / G	各 2–5	基礎但要拿穩

策略：先攻 B、C、H、I、J 五大戶（佔 MC 一半以上），A/E/F/G 用碎片時間補。试卷題目分佈零散，不能 tip 哪課不考，想拿 5/5* 必須全面。

Part 1 Microeconomics 微观经济

Unit 1 Basic Economic Concepts ★★★

本单元 Command Word 答题模板

Command Word	一-line 规则	本单元示例
State	仅1句官方定义，无需解释	Define scarcity. → "Scarcity is the condition that wants are unlimited but resources are limited."
Describe	趋势 + 对应图表数据引用	Describe a point inside the PPC. → "A point inside the PPC shows under-utilisation, e.g. unemployment of labour."
Explain	定义 + 因果推导（必须使用 because 逻辑链）	Explain opportunity cost. → "OC is the highest-valued option forgone because choosing one alternative means giving up the next best."
Discuss	正方论点 + 反方论点，无主观判断	Discuss whether growth is always desirable. → "For: more output; against: may harm the environment."
Evaluate	正反分析 + 个人合理评判（高分必备）	Evaluate the PPC model. → "PPC shows trade-offs clearly but assumes only two goods; on balance it is a useful tool despite simplification."

Term	Official English Definition	中文注解
Scarcity	The situation in which wants are unlimited but resources are limited	欲望无限而资源有限
Opportunity cost	The highest-valued option forgone when a choice is made	所放弃选项中价值最高者
Free good	A good with zero opportunity cost; at zero price, quantity supplied ≥ quantity demanded	零机会成本的物品
Economic good	A good with a positive opportunity cost	具正机会成本的物品
Positive statement	A statement about what is / what will be, which can be tested by facts	可用事实检验的实证陈述
Normative statement	A statement involving value judgement about what ought to be	含价值判断的规范陈述
Factors of production	Land, labour, capital and entrepreneurship used to produce goods and services	四大生产要素
Production possibility curve (PPC)	A curve showing the maximum combination of two goods an economy can produce given its resources and technology	生产可能性曲线，反映稀缺与取舍
Economic efficiency	A situation where resources are allocated to maximise the satisfaction of society's wants	资源已做最优配置

答题铁律：Opportunity cost 题必须写 "the highest-valued option forgone"，写 "the option given up" 不给满分。

经典陷阱：

• 免费得到的物品 ≠ free good（判断标准是机会成本，不是价格）
• Opportunity cost 只计 最高价值的一个 放弃选项，不是全部加总
• Positive 与 normative 的判别关键：能否用数据/事实证伪。带 "should / good / fair / ought" 等价值判断词的是 normative。

本单元必背官方定义（默写用）

① HKEAA Official Definition（一字不改原版英文）

Scarcity is the situation in which wants are unlimited but resources are limited.

② Exam Short Answer Sentence（2分简答默写短句，附中文注解）

简答默写："Scarcity means wants are unlimited while resources are limited, so every society must choose."（稀缺：欲望无限、资源有限，必须取舍。）

① HKEAA Official Definition（一字不改原版英文）

Opportunity cost is the highest-valued option forgone when a choice is made.

② Exam Short Answer Sentence（2分简答默写短句，附中文注解）

简答默写："The opportunity cost is the single highest-valued alternative given up, e.g. the $50 movie."（机会成本为所放弃选项中价值最高者，不能加总。）

How it works 核心机理

Scarcity forces every society to choose among alternatives, and choosing one option means giving up the next best alternative — that next best alternative is the opportunity cost. 所谓稀缺，是因为人的欲望无限而资源（土地、劳力、资本、企业家才能）有限，所以必须做取舍。The existence of opportunity cost is exactly what separates an economic good (positive opportunity cost) from a free good (zero opportunity cost). 在 PPC 上，任何一点都代表资源被充分利用；PPC 以内的点表示资源闲置，以外的点当前技术下不可达。当资源增加或技术进步时，整条 PPC 向外移动，代表经济能生产更多。理解稀缺与机会成本是整张经济科的地基，因为后面所有供需、政策取舍都建立在"有代价地放弃别的选择"之上。

Worked Example 1.1 — Opportunity Cost (2 marks)

Context: Tom has 1 hour. He can either (a) earn $80 tutoring, or (b) watch a movie he values at $50, or (c) sleep which he values at $30. He chooses tutoring.

Step 1: List the forgone options and their values: movie = $50, sleep = $30. (1 mark)
Step 2: Opportunity cost = highest-valued option forgone = $50 (the movie). State: "The opportunity cost is the movie valued at $50." (1 mark)

Worked Example 1.2 — Identifying a Free Good (2 marks)

A person picks up a fallen leaf in a park and keeps it. The leaf has zero price and collecting it requires no sacrifice of any other valued activity.

Step 1: Apply the test: does using this good mean giving up the next best alternative? Here, no time/resource of value is sacrificed. (1 mark)
Step 2: Since opportunity cost = 0, the leaf is a FREE good, not an economic good. State the defining criterion clearly. (1 mark)
Note: A free ticket to a concert is NOT a free good if attending it means giving up a paid shift — then its opportunity cost is the shift wage.

Worked Example 1.3 — Positive vs Normative (2 marks)

Statement A: "The minimum wage in Hong Kong should be raised to $50." Statement B: "Hong Kong's minimum wage was $40 in 2023."

Step 1: Classify A — contains "should", a value judgement about what ought to be → NORMATIVE statement. (1 mark)
Step 2: Classify B — a factual claim about the past, testable against government records → POSITIVE statement. (1 mark)
Scoring tip: Always underline the value word (should/ought/fair) to earn the classification mark.

Worked Example 1.4 — Ranking Forgone Options (3 marks)

Mary spends Saturday either (i) part-time job $200, (ii) study group she values $120, (iii) hiking she values $90. She chooses the study group.

Step 1: The chosen option is the study group, so the forgone options are job ($200) and hiking ($90). (1 mark)
Step 2: Among forgone, the highest-valued is the job at $200. (1 mark)
Step 3: Opportunity cost = $200 (the job), NOT $200 + $90. State: "OC is the single highest-valued alternative forgone = $200." (1 mark)

Worked Example 1.5 — PPC and Scarcity (3 marks)

An economy can produce at most 100 units of food OR 200 units of clothing if it devotes all resources to one good. Currently it produces 60 food and 120 clothing.

Step 1: Plot shows point inside the PPC is possible but indicates UNDER-utilisation of resources (e.g. unemployment). (1 mark)
Step 2: To get more food it must give up clothing — the slope gives the opportunity cost (here 2 clothing per 1 food). (1 mark)
Step 3: A point outside the current PPC is unattainable now; only economic growth (more resources / better tech) shifts PPC outward. (1 mark)

Common Trap：A free ticket or a gift is NOT automatically a free good. A free good must have zero opportunity cost — if using it means giving up something else valuable, it is an economic good. Also, opportunity cost is the SINGLE highest-valued alternative, never the sum of all alternatives. 另一常见错：把 positive statement 当 normative —— 只要句子可被事实检验（哪怕预测未来），就是 positive；只有带价值判断、无法证伪的主张才是 normative。

练习题库 Economics 卷见 /question-bank/economics/（A 单元基础概念题）。

Unit 2 Firms and Production ★★

本单元 Command Word 答题模板

Command Word	一-line 规则	本单元示例
State	仅1句官方定义，无需解释	Define division of labour. → "Division of labour means workers specialise in different stages of a production process."
Describe	趋势 + 对应图表数据引用	Describe diminishing marginal returns. → "As more workers are added to fixed capital, MP rises then falls, e.g. 14 → 9 → 5."
Explain	定义 + 因果推导（必须使用 because 逻辑链）	Explain economies of scale. → "Economies of scale occur because a larger output spreads fixed costs, lowering LRAC."
Discuss	正方论点 + 反方论点，无主观判断	Discuss sole proprietorship vs limited company. → "For: easy to set up; against: unlimited liability and limited capital."
Evaluate	正反分析 + 个人合理评判（高分必备）	Evaluate division of labour. → "It raises output but causes monotony; on balance beneficial where tasks are separable."

Term	Official English Definition	中文注解
Division of labour	Workers specialise in different stages of a production process	分工
Labour productivity	Output per worker in a period of time	人均产量
Limited liability	Shareholders' loss is limited to their capital contribution	有限责任
Private / Public limited company	Shares not / can be transferred publicly（私人公司股份不可公开转让）	私人/公众有限公司
Diminishing marginal returns	As more units of a variable factor are added to a fixed factor, the marginal product eventually falls	边际产量递减
Economies of scale	A fall in long-run average cost as output expands	规模经济
Sole proprietorship	A business owned and managed by one person who bears unlimited liability	独资

必背比较：Sole proprietorship vs Partnership vs Limited company —— 从 liability / legal entity / continuity / capital raising 四角度作答。

本单元必背官方定义（默写用）

① HKEAA Official Definition（一字不改原版英文）

Division of labour means workers specialise in different stages of a production process.

② Exam Short Answer Sentence（2分简答默写短句，附中文注解）

简答默写："Under division of labour, each worker repeats one task, raising output per worker."（分工：每人专做一道工序，提升人均产量。）

① HKEAA Official Definition（一字不改原版英文）

Economies of scale are a fall in long-run average cost as output expands.

② Exam Short Answer Sentence（2分简答默写短句，附中文注解）

简答默写："As output rises, LRAC falls, so the firm enjoys economies of scale."（规模经济：产量扩大令长期平均成本下降。）

How it works 核心机理

Division of labour raises output because workers repeat one task, build skill, and save time switching. 分工让工人专做一道工序，熟能生巧、减少换岗耗时，所以总产出上升。But beyond a point, adding more workers to a fixed amount of capital (land/machine) causes diminishing marginal returns — each extra worker adds less output than the previous one. 注意区分：marginal product（边际产量）下降不等于 total product 下降——总产量仍可上升，只是升得越来越慢。在 long run 所有要素都可变，此时看 economies of scale：产量扩大令平均成本下降才是规模经济，与短期的边际产量递减是两套概念，考生极易混。

Worked Example 2.1 — Labour Productivity (2 marks)

A factory employs 10 workers and produces 1,000 units per day. After hiring 5 more workers (total 15) with no extra machines, output rises to 1,350 units per day.

Step 1: Initial productivity = 1,000 ÷ 10 = 100 units/worker/day. (1 mark)
Step 2: New productivity = 1,350 ÷ 15 = 90 units/worker/day. State that productivity FALLS because of diminishing marginal returns. (1 mark)

Worked Example 2.2 — Marginal Product Table (3 marks)

A fixed farm uses 1,2,3,4 workers. Total product = 10, 24, 33, 38 units.
Step 1: MP of 1st worker = 10 − 0 = 10. (1 mark)
Step 2: MP of 2nd = 24 − 10 = 14; MP of 3rd = 33 − 24 = 9; MP of 4th = 38 − 33 = 5. (1 mark)
Step 3: MP rises then falls → law of diminishing marginal returns sets in after the 2nd worker. State conclusion. (1 mark)

Worked Example 2.3 — Division of Labour Benefit (2 marks)

A pin factory splits pin-making into 10 specialised tasks instead of each worker making a whole pin.

Step 1: Identify three benefits: (a) skill gain from repetition, (b) time saved not switching tasks, (c) machinery suited to one narrow task. (1 mark)
Step 2: Conclude total output per worker rises — this is the classic Smithian division-of-labour argument. (1 mark)

Worked Example 2.4 — Business Form Comparison (4 marks)

Compare sole proprietorship and public limited company on four dimensions.
Step 1: Liability — sole prop has UNLIMITED liability; plc has LIMITED liability. (1 mark)
Step 2: Legal entity — sole prop is NOT separate from owner; plc IS a separate legal entity. (1 mark)
Step 3: Continuity — sole prop ends if owner dies; plc continues regardless of shareholders. (1 mark)
Step 4: Capital raising — sole prop limited to owner's funds/loans; plc can raise large capital by selling shares to public. (1 mark)

Worked Example 2.5 — Economies of Scale (3 marks)

A firm's long-run average cost falls from $20 to $14 as output rises from 1,000 to 5,000 units.
Step 1: Falling LRAC with rising output = economies of scale present. (1 mark)
Step 2: Possible sources: bulk-buying discounts, specialised machinery, division of labour, lower cost of capital. (1 mark)
Step 3: Note this is a LONG-RUN concept (all inputs variable), distinct from short-run diminishing returns. (1 mark)

Common Trap：More workers does NOT automatically mean higher productivity per worker. If capital is fixed, the law of diminishing marginal returns applies, so average labour productivity can fall even when total output rises. 另：economies of scale（长期平均成本降）与 diminishing marginal returns（短期边际产量降）是不同时间段的概念，卷二 essay 常要求区分，即 confusing them will lose comparative marks。

练习题库 Economics 卷见 /question-bank/economics/（B 单元生产理论）。

Unit 3 Demand, Supply and Price Determination ★★★

💡 写 DRQ 前先回看本单元 Command Word 模板与上方 DRQ 强制提醒。

本单元 Command Word 答题模板

Command Word	一-line 规则	本单元示例
State	仅1句官方定义，无需解释	Define equilibrium price. → "The equilibrium price is the price at which quantity demanded equals quantity supplied."
Describe	趋势 + 对应图表数据引用	Describe a demand increase. → "Demand rises, D shifts right, e.g. P0 20 → 30, Q 60 → 80."
Explain	定义 + 因果推导（必须使用 because 逻辑链）	Explain why shortage raises price. → "Shortage occurs because at a price below equilibrium Qd > Qs, so buyers bid the price up."
Discuss	正方论点 + 反方论点，无主观判断	Discuss price controls. → "For ceiling: protects consumers; against: causes shortage and black market."
Evaluate	正反分析 + 个人合理评判（高分必备）	Evaluate the price mechanism. → "It allocates efficiently but ignores equity; on balance use the market with minimal intervention."

Term	Official English Definition	中文注解
Law of demand	When the price of a good rises, the quantity demanded falls, ceteris paribus	需求定律
Change in demand vs quantity demanded	Demand shifts due to non-price factors; quantity demanded moves along the curve due to price	整条曲线移动 vs 沿线移动
Equilibrium price	The price at which quantity demanded = quantity supplied	均衡价格
Shortage / Surplus	Qd > Qs at a price below equilibrium / Qs > Qd above equilibrium	短缺 / 过剩
Law of supply	When the price of a good rises, the quantity supplied rises, ceteris paribus	供给定律
Excess demand / excess supply	Another name for shortage / surplus at a disequilibrium price	超额需求 / 超额供给

Diagram 满分四要件（缺一扣分）：

1. 轴标签：Price ($) 纵轴、Quantity 横轴
2. 曲线标签：D₀ → D₁、S₀ → S₁
3. 均衡点：标 E₀ → E₁，虚线投影到两轴标 P₀ P₁ Q₀ Q₁
4. 箭头标明移动方向

标准分析三句式（供求变化题万能模板）：

1. The [event] leads to an increase/decrease in demand/supply.
2. The demand/supply curve shifts rightward/leftward from D0 to D1.
3. As a result, the equilibrium price rises/falls from P0 to P1 and the equilibrium quantity increases/decreases from Q0 to Q1.

非价格因素清单（必背）：

• Demand shifters：income、price of related goods（substitutes/complements）、tastes、expectations、number of buyers
• Supply shifters：cost of production、technology、tax/subsidy、expectations、number of sellers、weather（农产品）

本单元必背官方定义（默写用）

① HKEAA Official Definition（一字不改原版英文）

The equilibrium price is the price at which quantity demanded equals quantity supplied.

② Exam Short Answer Sentence（2分简答默写短句，附中文注解）

简答默写："At the equilibrium price, Qd = Qs and the market clears with no shortage or surplus."（均衡价下需求量等于供给量，市场出清。）

① HKEAA Official Definition（一字不改原版英文）

When the price of a good rises, the quantity demanded falls, ceteris paribus.

② Exam Short Answer Sentence（2分简答默写短句，附中文注解）

简答默写："A rise in price causes a movement along the demand curve, lowering quantity demanded."（需求定律：价升量减，沿曲线移动。）

How it works 核心机理

Price is the signal that clears the market. 价格是协调买卖双方的信号。When price is below equilibrium, Qd > Qs (shortage) and buyers bid the price up; when above, Qs > Qd (surplus) and sellers cut price. 市场靠价格自发调节：短缺时买家愿出更高价，价格上升；过剩时卖家降价求售，价格回落。The market moves toward the equilibrium where Qd = Qs. 关键是分清楚"整条曲线移动"（因非价格因素）与"沿曲线移动"（只因本身价格变了）——前者改 demand/supply，后者改 quantity demanded/supplied，这是 DSE 最常考的定义分。记住：题目若写 "income rises"，那是 demand 整条移；若写 "price falls"，那是 quantity demanded 沿线移。

Worked Example 3.1 — Finding Equilibrium (3 marks)

Demand: Qd = 100 − 2P. Supply: Qs = 20 + 2P. Find equilibrium price and quantity.

Step 1: At equilibrium, Qd = Qs, so 100 − 2P = 20 + 2P. (1 mark)
Step 2: Rearrange: 100 − 20 = 2P + 2P → 80 = 4P → P = 20. (1 mark)
Step 3: Substitute P = 20 into either equation: Qd = 100 − 40 = 60. Equilibrium: P = $20, Q = 60. (1 mark)

Worked Example 3.2 — Shift in Demand (4 marks)

Initial: Qd = 100 − 2P, Qs = 20 + 2P (equilibrium P = 20, Q = 60). Consumers' income rises, new demand: Qd = 140 − 2P.

Step 1: New equilibrium: 140 − 2P = 20 + 2P → 120 = 4P → P = 30. (1 mark)
Step 2: Q = 20 + 2(30) = 80. New equilibrium P = $30, Q = 80. (1 mark)
Step 3: Demand shifted RIGHT (income is a non-price factor ↑). State which shifter. (1 mark)
Step 4: Conclusion sentence: Rise in income increases demand → D shifts right → P rises 20→30, Q rises 60→80. (1 mark)

Worked Example 3.3 — Shift in Supply (4 marks)

Same base, but a rise in wage (cost of production) cuts supply to Qs = −10 + 2P.
Step 1: New equilibrium: 100 − 2P = −10 + 2P → 110 = 4P → P = 27.5. (1 mark)
Step 2: Q = 100 − 2(27.5) = 45. New P = $27.5, Q = 45. (1 mark)
Step 3: Supply shifted LEFT (cost ↑ reduces supply). (1 mark)
Step 4: Conclusion: Higher production cost decreases supply → S left → P up 20→27.5, Q down 60→ (Q=45). (1 mark)

Worked Example 3.4 — Shortage Calculation (3 marks)

At a controlled price P = 15: Qd = 100 − 2(15) = 70; Qs = 20 + 2(15) = 50.
Step 1: Since P = 15 < equilibrium 20, market is below equilibrium → shortage. (1 mark)
Step 2: Shortage = Qd − Qs = 70 − 50 = 20 units (excess demand). (1 mark)
Step 3: State: "At P = 15 there is a shortage of 20; price will be bid up toward 20." (1 mark)

Worked Example 3.5 — Distinguish Shift vs Movement (2 marks)

"The price of coffee rises, so quantity demanded of coffee falls."
Step 1: This is a MOVEMENT ALONG the demand curve, not a shift — only the good's own price changed. (1 mark)
Step 2: It is a change in QUANTITY DEMANDED, correctly labelled, earning the definition mark. (1 mark)

Common Trap："Change in demand" means the whole curve SHIFTS (non-price factor like income). "Change in quantity demanded" means a MOVE ALONG the same curve caused by a price change. Mixing these up loses the definition mark and breaks the whole diagram explanation. 记住：描述"需求上升"要用 demand increases / curve shifts right；描述"需求量增加"要用 quantity demanded rises / movement along curve。两套术语不可互换。

练习题库 Economics 卷见 /question-bank/economics/（C 单元供需作图题）。

Unit 4 Elasticity ★★★

本单元 Command Word 答题模板

Command Word	一-line 规则	本单元示例
State	仅1句官方定义，无需解释	Define price elasticity of demand. → "PED is the responsiveness of Qd to a price change, = %ΔQd ÷ %ΔP."
Describe	趋势 + 对应图表数据引用	Describe TR when Ed > 1. → "When demand is elastic, a price rise lowers TR, e.g. $1,000 → $840."
Explain	定义 + 因果推导（必须使用 because 逻辑链）	Explain why inelastic demand raises TR on price rise. → "TR rises because the % fall in Q is smaller than the % rise in P, so P × Q increases."
Discuss	正方论点 + 反方论点，无主观判断	Discuss taxing inelastic goods. → "For: raises revenue with small Q loss; against: hurts less-responsive consumers."
Evaluate	正反分析 + 个人合理评判（高分必备）	Evaluate using Ed in pricing. → "Firms should raise price only if demand is inelastic; on balance Ed is essential for revenue."

Concept	Formula	Interpretation
Price elasticity of demand (Ed)	%ΔQd ÷ %ΔP	Ed > 1 elastic; Ed < 1 inelastic; Ed = 1 unitary
Price elasticity of supply (Es)	%ΔQs ÷ %ΔP	同上判读
Income elasticity of demand (Yed)	%ΔQd ÷ %ΔY	Yed > 0 normal; < 0 inferior
Cross elasticity of demand (Xed)	%ΔQd of A ÷ %ΔP of B	Xed > 0 substitute; < 0 complement

总收入判定表（必背）：

需求弹性	提价后 Total Revenue	降价后 Total Revenue
Elastic (Ed>1)	↓ falls	↑ rises
Inelastic (Ed<1)	↑ rises	↓ falls
Unitary (Ed=1)	unchanged	unchanged

标准句式：Since the demand is price elastic, an increase in price leads to a more than proportionate decrease in quantity demanded, so total revenue falls.

本单元必背官方定义（默写用）

① HKEAA Official Definition（一字不改原版英文）

Price elasticity of demand = % change in quantity demanded ÷ % change in price.

② Exam Short Answer Sentence（2分简答默写短句，附中文注解）

简答默写："If |PED| > 1, demand is elastic; a price rise lowers total revenue because Q falls more than P rises."（弹性>1：提价令总收益降。注意取绝对值。）

How it works 核心机理

Elasticity measures how responsive quantity is to a price change. 弹性衡量"量变对价变有多敏感"。The key exam trick: total revenue = P × Q. If demand is inelastic (Ed < 1), the % change in Q is smaller than the % change in P, so a price rise raises TR. 直观讲：缺乏弹性时买家不太会因涨价而少买，所以总价（单价×数量）反而升。If elastic (Ed > 1), the Q effect dominates and a price rise lowers TR. 富有弹性时买家对价格敏感，小幅涨价就流失大量销量，总价下降。Yed 区分 normal（收入升需求升）与 inferior 品；Xed 正负则区分 substitute 与 complement——这些是 MC 高频比较点。

Worked Example 4.1 — PED and Total Revenue (4 marks)

Price rises from $10 to $12. Quantity demanded falls from 100 to 70.
(a) Calculate PED. (b) State whether demand is elastic or inelastic. (c) What happens to total revenue?

Step 1: %ΔP = (12 − 10)/10 × 100% = +20%. (1 mark)
Step 2: %ΔQd = (70 − 100)/100 × 100% = −30%. (1 mark)
Step 3: PED = |−30% ÷ 20%| = 1.5 → price elastic. (1 mark)
Step 4: TR₀ = 10 × 100 = $1,000; TR₁ = 12 × 70 = $840. TR falls by $160, consistent with elastic demand. (1 mark)

Worked Example 4.2 — PES Calculation (3 marks)

Price of wheat rises 10%, quantity supplied rises 25%.
Step 1: Es = %ΔQs ÷ %ΔP = 25% ÷ 10% = 2.5. (1 mark)
Step 2: Es > 1 → supply is price ELASTIC (farmers can expand output relatively easily here). (1 mark)
Step 3: Contrast: if Es < 1 supply inelastic (e.g. land fixed in short run). (1 mark)

Worked Example 4.3 — Income Elasticity (3 marks)

Income rises 5%, demand for restaurant meals rises 8%.
Step 1: Yed = %ΔQd ÷ %ΔY = 8% ÷ 5% = 1.6. (1 mark)
Step 2: Yed > 0 → restaurant meals are a NORMAL good. (1 mark)
Step 3: Yed > 1 → it is a luxury normal good (demand grows faster than income). (1 mark)

Worked Example 4.4 — Cross Elasticity (3 marks)

Price of tea rises 10%, quantity demanded of coffee rises 6%.
Step 1: Xed = %ΔQd(coffee) ÷ %ΔP(tea) = 6% ÷ 10% = 0.6. (1 mark)
Step 2: Xed > 0 → tea and coffee are SUBSTITUTES. (1 mark)
Step 3: A rise in tea price diverts some demand to coffee, raising coffee's Qd. (1 mark)

Worked Example 4.5 — Inelastic Pricing Strategy (3 marks)

Petrol has Ed = 0.4. A station raises price 10%.
Step 1: %ΔQd = Ed × %ΔP = 0.4 × 10% = 4% fall in quantity. (1 mark)
Step 2: TR effect: price +10%, quantity −4%, so TR ≈ 1.10 × 0.96 = 1.056 → TR rises ~5.6%. (1 mark)
Step 3: Conclusion: for inelastic goods, raising price increases total revenue — explains why essential commodities can be taxed heavily. (1 mark)

Common Trap：Always take the absolute value of PED (it is almost always negative because of the law of demand). The classification uses |PED|: >1 elastic, <1 inelastic. Also, never judge elasticity by the slope of the demand curve alone — a steep curve can still be elastic at high-price ranges. 斜率是斜率、弹性是"相对变动比例"，两者不同；靠近纵轴高价段即使曲线陡，弹性也可能很大。另：Yed 负值是 inferior 品（收入升反而需求降，如廉价方便面），这是常考但易漏的点。

练习题库 Economics 卷见 /question-bank/economics/（弹性计算题）。

Unit 5 Market Intervention ★★★

💡 写 DRQ 前先回看本单元 Command Word 模板与上方 DRQ 强制提醒。

本单元 Command Word 答题模板

Command Word	一-line 规则	本单元示例
State	仅1句官方定义，无需解释	Define price ceiling. → "A price ceiling is a legal maximum price set below equilibrium, causing a shortage."
Describe	趋势 + 对应图表数据引用	Describe tax incidence. → "The wedge splits between buyers and sellers, e.g. Pb 11, Ps 9, tax 2."
Explain	定义 + 因果推导（必须使用 because 逻辑链）	Explain why tax falls more on the inelastic side. → "The more inelastic side bears more because it cannot easily change Q when price moves."
Discuss	正方论点 + 反方论点，无主观判断	Discuss price floors. → "For: protects producers' income; against: creates surplus needing govt purchase."
Evaluate	正反分析 + 个人合理评判（高分必备）	Evaluate market intervention. → "It corrects failure but creates DWL; on balance justified only for clear market failure."

Term	Official English Definition	中文注解
Price ceiling (effective)	A legal maximum price set below the equilibrium price → shortage	有效价格上限 → 短缺
Price floor (effective)	A legal minimum price set above the equilibrium price → surplus	有效价格下限 → 过剩
Quota	A legal limit on quantity supplied	配额
Unit tax incidence	Shared between buyers and sellers depending on relative elasticities	从量税负担按相对弹性分摊
Subsidy	A payment by government to producers/consumers that lowers effective cost	补贴
Deadweight loss of intervention	The net loss of social surplus caused by the intervention	干预造成的无谓损失

税负分摊规则：需求越缺乏弹性（inelastic），买方承担越多税负。句式：The more inelastic the demand, the larger the share of tax borne by buyers.

本单元必背官方定义（默写用）

① HKEAA Official Definition（一字不改原版英文）

A price ceiling is a legal maximum price set below the equilibrium price, causing a shortage.

② Exam Short Answer Sentence（2分简答默写短句，附中文注解）

简答默写："An effective price ceiling below P* creates excess demand (shortage) of Qd − Qs."（有效价格上限低于均衡价，造成短缺。）

① HKEAA Official Definition（一字不改原版英文）

A price floor is a legal minimum price set above the equilibrium price, causing a surplus.

② Exam Short Answer Sentence（2分简答默写短句，附中文注解）

简答默写："An effective price floor above P* creates excess supply (surplus) of Qs − Qd."（有效价格下限高于均衡价，造成过剩。）

How it works 核心机理

A price ceiling below equilibrium makes the legal price too low, so Qd exceeds Qs → shortage (excess demand). 价格上限压在低处，买家想买多、卖家想卖少，于是短缺。A price floor above equilibrium makes the legal price too high, so Qs exceeds Qd → surplus (excess supply). 价格下限抬高处，卖家想卖多、买家想买少，于是过剩（如最低工资造成失业、农产品收购价造成库存）。For a tax, the burden splits according to relative elasticities: the side that is less elastic (less able to escape by changing quantity) pays more. 税负的真正归属由"谁更难用改变数量来逃避"决定——越缺乏弹性的一方越逃不掉，承担越多。补贴则相反，其利益也按相对弹性分配。

Worked Example 5.1 — Tax Incidence (3 marks)

A $2 per-unit tax is imposed on Good Y. Before tax, equilibrium P = $10, Q = 100. After tax, buyers pay Pb = $11 and sellers receive Ps = $9. The tax = Pb − Ps = $2.

Step 1: Buyers' burden = Pb − original P = 11 − 10 = $1 per unit. (1 mark)
Step 2: Sellers' burden = original P − Ps = 10 − 9 = $1 per unit. (1 mark)
Step 3: Burden shared equally → demand and supply have similar elasticities. State: "Tax incidence depends on relative elasticities, not on who legally pays the tax." (1 mark)

Worked Example 5.2 — Price Ceiling Shortage (4 marks)

Equilibrium P* = $8, Q* = 100. A price ceiling is set at $5.
Demand at $5: Qd = 130. Supply at $5: Qs = 70.
Step 1: Ceiling ($5) < P* ($8) → effective ceiling, binding. (1 mark)
Step 2: At $5, Qd (130) > Qs (70) → shortage = 60 units. (1 mark)
Step 3: Only Qs = 70 actually traded (sellers won't supply more at the low price). (1 mark)
Step 4: Conclude: effective price ceiling creates excess demand of 60; may lead to black market at prices above $5. (1 mark)

Worked Example 5.3 — Price Floor Surplus (4 marks)

Equilibrium P* = $8, Q* = 100. A price floor is set at $12 (e.g. minimum wage / farm support).
Demand at $12: Qd = 60. Supply at $12: Qs = 140.
Step 1: Floor ($12) > P* ($8) → effective floor, binding. (1 mark)
Step 2: At $12, Qs (140) > Qd (60) → surplus = 80 units. (1 mark)
Step 3: Only Qd = 60 traded; 80 units unsold / unemployed workers. (1 mark)
Step 4: Conclude: effective price floor creates excess supply of 80; government may need to buy the surplus. (1 mark)

Worked Example 5.4 — Quota Effect (3 marks)

Free-market equilibrium Q = 100. A quota limits total quantity to 60.
Step 1: Quota caps quantity below equilibrium → like a supply restriction. (1 mark)
Step 2: Price rises above equilibrium (shortage at the capped quantity bids price up). (1 mark)
Step 3: Quota licence holders gain rent; consumers lose; deadweight loss triangle appears. (1 mark)

Worked Example 5.5 — Inelastic Demand Bears More Tax (3 marks)

Good Z has very inelastic demand, elastic supply. A $3 tax is imposed.
Step 1: Because demand is inelastic, buyers cannot easily reduce Q when price rises. (1 mark)
Step 2: So most of the $3 wedge is passed to buyers: Pb rises close to $3, Ps barely falls. (1 mark)
Step 3: Conclusion: "The more inelastic the demand, the larger the share of tax borne by buyers" — here buyers bear the bulk. (1 mark)

Common Trap：Whoever the government legally charges the tax to does NOT determine who really bears it. The economic burden is decided by relative price elasticity of demand and supply. Also, an "effective" price ceiling must be BELOW equilibrium; if set above, it is non-binding and creates no shortage. 同理，price floor 若设在均衡价以下就是非约束性的（no effect）。考生常把"政府向卖家征税"误以为卖家全担——错；看弹性。

练习题库 Economics 卷见 /question-bank/economics/（E 单元市场失效图分析题）。

Unit 6 Efficiency and Market Failure ★★

💡 写 DRQ 前先回看本单元 Command Word 模板与上方 DRQ 强制提醒。

本单元 Command Word 答题模板

Command Word	一-line 规则	本单元示例
State	仅1句官方定义，无需解释	Define externality. → "An externality is a cost or benefit imposed on third parties not involved in the transaction."
Describe	趋势 + 对应图表数据引用	Describe a negative externality diagram. → "MSC lies above MPC, e.g. MSC 8 > MPC 5 at Q = 100."
Explain	定义 + 因果推导（必须使用 because 逻辑链）	Explain why overproduction occurs. → "Overproduction occurs because producers ignore external cost, so MSC > MSB at market output."
Discuss	正方论点 + 反方论点，无主观判断	Discuss merit-good provision. → "For: corrects under-consumption; against: gov may misjudge the optimal quantity."
Evaluate	正反分析 + 个人合理评判（高分必备）	Evaluate a Pigouvian tax. → "It internalises the externality but needs accurate cost data; on balance effective when the externality is large."

• Marginal benefit (MB) / Marginal cost (MC)：边际效益 / 边际成本
• Efficiency criterion：Social surplus is maximised when MB = MC
• Deadweight loss：因产量偏离效率水平而损失的社会盈余
• Externality：A cost or benefit imposed on third parties not involved in the transaction（外部性）
• 政府纠正手段：tax / subsidy / regulation / tradable permits
• Merit good：A good whose social benefit exceeds private benefit（社会益大于私人益，如教育）
• Demerit good：A good whose social cost exceeds private cost（社会害大于私人害，如香烟）

本单元必背官方定义（默写用）

① HKEAA Official Definition（一字不改原版英文）

An externality is a cost or benefit imposed on third parties not involved in the transaction.

② Exam Short Answer Sentence（2分简答默写短句，附中文注解）

简答默写："A negative externality means MSC > MPC, so the market overproduces and a deadweight loss appears."（负外部性：社会成本高于私人成本，生产过多。）

① HKEAA Official Definition（一字不改原版英文）

A merit good is a good whose social benefit exceeds private benefit.

② Exam Short Answer Sentence（2分简答默写短句，附中文注解）

简答默写："A merit good is under-consumed because MSB > MPB, so the government should subsidise it."（ merit 物品：社会益大于私人益，消费不足，应补贴。）

How it works 核心机理

Efficiency is achieved where marginal social benefit (MSB) = marginal social cost (MSC); at this point social surplus is maximised. 效率点在 MSB = MSC，此时社会总剩余最大。A negative externality means MSC > MPC, so the market produces too much (overproduction) and a deadweight loss triangle appears between MSB and MSC. 负外部性下私人忽视对第三方的成本，生产过多，DWL 三角出现。A positive externality means MSB > MPB, so the market produces too little. 正外部性下（如教育）市场生产不足。政府纠正：对负外部性征税（Pigouvian tax）把 MPC 抬向 MSC；对正外部性给补贴把 MPB 抬向 MSB；或用 regulation、可交易许可证。Merit/demerit goods 是外部性的特例，分别导致 under/over-consumption。

Worked Example 6.1 — Identifying Market Failure (3 marks)

A factory emits smoke. Its private MC of the 100th unit is $5, but the smoke imposes $3 extra cost on neighbours. The good is sold at the price where MPB = MPC ($5).

Step 1: MSC = MPC + external cost = 5 + 3 = $8. (1 mark)
Step 2: At Q = 100, MSC ($8) > MSB (= price $5 at that output). The market overproduces. (1 mark)
Step 3: Remedy: impose a Pigouvian tax of $3 per unit to internalise the externality, shifting MPC toward MSC. (1 mark)

Worked Example 6.2 — Positive Externality Underproduction (3 marks)

Education: MPB of the 50th student = $4, but MSB = $7 (society also gains). MPC = $4.
Step 1: Market equilibrates at MPB = MPC → Q = 50. (1 mark)
Step 2: Efficient output is where MSB = MSC; here MSB ($7) > MPC ($4) at Q=50, so socially optimal Q > 50. (1 mark)
Step 3: Market UNDER-produces education → remedy is a subsidy to raise MPB toward MSB. (1 mark)

Worked Example 6.3 — Deadweight Loss Size (3 marks)

At the market output Qm = 100, MSC = $8, MSB = $5. At the efficient output Qe = 70, MSC = MSB = $6.
Step 1: Overproduction = Qm − Qe = 30 units. (1 mark)
Step 2: DWL ≈ ½ × (Qm − Qe) × (MSC − MSB at Qm) = ½ × 30 × (8 − 5) = 45. (1 mark)
Step 3: State the triangle lies between MSC and MSB from Qe to Qm; it is lost social surplus. (1 mark)

Worked Example 6.4 — Subsidy Remedy (3 marks)

Vaccination has MSB = $20, MPB = $12 per dose; MPC = $12.
Step 1: Market produces where MPB = MPC → Q = Qm, but efficient Qe is where MSB = MSC. (1 mark)
Step 2: Gap MSB − MPB = $8, so a per-unit subsidy of $8 raises MPB (net cost to consumer) toward MSB. (1 mark)
Step 3: Subsidy internalises the positive externality, moving output from Qm toward Qe, removing the DWL. (1 mark)

Worked Example 6.5 — Merit vs Demerit Goods (2 marks)

Cigarettes: smokers ignore health cost to others; society bears extra cost.
Step 1: Cigarettes are a DEMERIT good → MSB < MPB, over-consumed → tax/ban/warning labels. (1 mark)
Step 2: Education is a MERIT good → MSB > MPB, under-consumed → subsidy/compulsory provision. (1 mark)

Common Trap：Do not confuse "external cost" with "externality". An externality is the effect on third parties; the market failure is over- or under-production relative to the MSB = MSC point. Also, deadweight loss is the LOSS of social surplus, not merely "waste" — in essays you must show the triangle on the diagram. 另：merit/demerit 归类时，判断标准是 social 与 private 的 benefit/cost 谁大，别只凭"好/坏"直觉答。

练习题库 Economics 卷见 /question-bank/economics/（E 单元市场失效图分析题）。

Unit 7 Measurement of Economic Performance ★★★

本单元 Command Word 答题模板

Command Word	一-line 规则	本单元示例
State	仅1句官方定义，无需解释	Define GDP. → "GDP is the total market value of all final goods and services produced within the domestic territory in a period."
Describe	趋势 + 对应图表数据引用	Describe real GDP adjustment. → "Real GDP removes the price effect, e.g. nominal 500 → real 400 at index 125."
Explain	定义 + 因果推导（必须使用 because 逻辑链）	Explain why second-hand sales are excluded. → "They are excluded because already counted when first produced, so including them double-counts."
Discuss	正方论点 + 反方论点，无主观判断	Discuss per capita real GDP as living standard. → "For: simple cross-country proxy; against: ignores distribution and non-market work."
Evaluate	正反分析 + 个人合理评判（高分必备）	Evaluate GDP as a welfare measure. → "GDP measures output but not welfare; on balance useful yet incomplete without distribution data."

Term	Official English Definition	中文注解
GDP	The total market value of all final goods and services produced within the domestic territory in a period	本地生产总值（注意三关键词）
GNP/GNI	GDP + factor income earned by residents from abroad − factor income earned by non-residents domestically	国民生产总值
Nominal vs Real GDP	Real GDP is measured at constant prices, removing the effect of price changes	实质GDP剔除物价影响
Per capita real GDP	Real GDP ÷ population, a rough indicator of living standard	人均实质GDP
GDP deflator	(Nominal GDP ÷ Real GDP) × 100, a price index	GDP平减指数
Underground economy	Economic activity not recorded in official GDP (e.g. illegal / unreported work)	地下经济，不计入GDP

GDP 不包含（高频陷阱）：二手货交易、纯金融转移（股票买卖差价）、家务劳动、非法交易、中间产品。

本单元必背官方定义（默写用）

① HKEAA Official Definition（一字不改原版英文）

GDP is the total market value of all final goods and services produced within the domestic territory in a period.

② Exam Short Answer Sentence（2分简答默写短句，附中文注解）

简答默写："GDP counts only final goods produced within the territory in a period to avoid double-counting."（GDP 只计境内当期最终产品，避免重复计算中间品。）

How it works 核心机理

GDP counts only FINAL goods and services produced within a territory in a period, to avoid double-counting intermediate goods. 只计 final goods 是为了避免把中间产品重复算入（如面粉做面包只算面包）。Real GDP adjusts nominal GDP by a price index so we can compare living standards across years without the illusion of "growth" that is just inflation. 名义 GDP 涨可能只是物价涨，实质 GDP 用常数价格剔除物价，才能看真实产出与生活水平。Per capita real GDP = 实质 GDP ÷ 人口，是生活水平的粗略指标（但忽略分配不均与环境成本）。GNP/GNI 则按"居民"而非"境内"算，要加上海外净要素收入。

Worked Example 7.1 — Real GDP (3 marks)

Nominal GDP in 2023 = $500bn, price index (2023, base 2020 = 100) = 125. Calculate real GDP in 2020 prices.

Step 1: Real GDP = Nominal GDP ÷ (Price index ÷ 100). (1 mark)
Step 2: Real GDP = 500 ÷ (125 ÷ 100) = 500 ÷ 1.25. (1 mark)
Step 3: Real GDP = $400bn (in 2020 constant prices). (1 mark)

Worked Example 7.2 — GDP Exclusion (3 marks)

Which of these are counted in this year's GDP? (a) sale of a 2020 second-hand car, (b) a new house built this year, (c) you cooking your own dinner.
Step 1: (a) excluded — second-hand good, already counted when new. (1 mark)
Step 2: (b) included — newly produced final good/service this year. (1 mark)
Step 3: (c) excluded — non-market household work not sold, not in GDP. (1 mark)

Worked Example 7.3 — GNP vs GDP (3 marks)

A country's GDP = $1,000bn. Its firms earn $40bn abroad; foreign firms earn $30bn domestically.
Step 1: GNP = GDP + net factor income from abroad = 1000 + (40 − 30). (1 mark)
Step 2: GNP = 1000 + 10 = $1,010bn. (1 mark)
Step 3: GNP > GDP here because residents earn more abroad than foreigners earn domestically. (1 mark)

Worked Example 7.4 — Per Capita Real GDP (3 marks)

Real GDP = $400bn, population = 5 million. Next year real GDP = $420bn, population = 5.04 million.
Step 1: Year1 per capita = 400bn ÷ 5m = $80,000. (1 mark)
Step 2: Year2 per capita = 420bn ÷ 5.04m = $83,333. (1 mark)
Step 3: Living standard (proxy) rose ~4.2%, even though population also grew. (1 mark)

Worked Example 7.5 — GDP Deflator (3 marks)

Nominal GDP = $520bn, Real GDP = $400bn (base year).
Step 1: GDP deflator = (Nominal ÷ Real) × 100 = (520 ÷ 400) × 100 = 130. (1 mark)
Step 2: Deflator > 100 means overall price level is 30% above base year. (1 mark)
Step 3: The 30% gap between nominal and real growth is pure price inflation, not output growth. (1 mark)

Common Trap：Nominal GDP can rise simply because prices rose, not because output grew. If the question asks about "living standards" or "real growth", you MUST use real GDP, not nominal. Also, GDP excludes non-market household work and second-hand sales — including them is a classic overcounting error. 另：GNP 与 GDP 的口径差异（居民 vs 境内）常在 MC 考，别混淆。

练习题库 Economics 卷见 /question-bank/economics/（F 单元 GDP 计算与辨析）。

Unit 8 National Income Determination ★★

💡 写 DRQ 前先回看本单元 Command Word 模板与上方 DRQ 强制提醒。

本单元 Command Word 答题模板

Command Word	一-line 规则	本单元示例
State	仅1句官方定义，无需解释	Define the multiplier. → "The multiplier is the ratio of the total change in national income to the initial injection, k = 1 ÷ (1 − MPC)."
Describe	趋势 + 对应图表数据引用	Describe the multiplier effect. → "An injection of $100 with k = 5 raises Y by $500."
Explain	定义 + 因果推导（必须使用 because 逻辑链）	Explain why the multiplier exceeds one. → "It exceeds one because the initial injection becomes income partly spent again, creating further rounds."
Discuss	正方论点 + 反方论点，无主观判断	Discuss expansionary fiscal policy. → "For: closes a deflationary gap; against: may raise debt and future taxes."
Evaluate	正反分析 + 个人合理评判（高分必备）	Evaluate fiscal policy in HK. → "HK lacks independent monetary policy so fiscal leads; on balance fiscal is HK's main stabiliser."

• Aggregate demand: AD = C + I + G + X − M
• Consumption function、MPC/MPS、乘数：Multiplier k = 1/(1−MPC)
• Deflationary / Inflationary gap 与对应的财政政策方向
• Withdrawals (W) = S + T + M；Injections (J) = I + G + X
• Average propensity to consume (APC) = C ÷ Y；APS = S ÷ Y

本单元必背官方定义（默写用）

① HKEAA Official Definition（一字不改原版英文）

The multiplier is the ratio of the total change in national income to the initial change in injection, k = 1 ÷ (1 − MPC).

② Exam Short Answer Sentence（2分简答默写短句，附中文注解）

简答默写："With MPC = 0.8, k = 1 ÷ (1 − 0.8) = 5, so a $100 injection raises Y by $500."（乘数 = 1 ÷ (1 − MPC)；初始注入层层递推放大产出。）

How it works 核心机理

AD = C + I + G + (X − M). An injection such as higher G raises national income, but the total rise in income is larger than the initial injection because the extra income is partly spent again — this is the multiplier effect. 初始注入（如政府多花 $100）变成受惠者收入，他们又按 MPC 消费，层层递推。The multiplier k = 1 ÷ (1 − MPC) = 1 ÷ MPS. 漏出越多（储蓄、税、进口），每轮留下的消费越少，乘数越小。若经济体存在 deflationary gap（AD 不足、失业），应扩财政把 AD 右推；若存在 inflationary gap（AD 过旺、通胀），应紧财政。开放经济下乘数公式要加入税率与进口倾向，否则会高估。

Worked Example 8.1 — The Multiplier (4 marks)

MPC = 0.8. The government increases spending by $100 million. Calculate the total change in national income.

Step 1: MPS = 1 − MPC = 1 − 0.8 = 0.2. (1 mark)
Step 2: Multiplier k = 1 ÷ MPS = 1 ÷ 0.2 = 5. (1 mark)
Step 3: Total ΔY = k × ΔG = 5 × 100 = $500 million. (1 mark)
Step 4: Conclude: national income rises by $500m, five times the initial injection. (1 mark)

Worked Example 8.2 — MPC and Induced Consumption (3 marks)

Consumption function: C = 100 + 0.75Y. At Y = 400, find C and APC.
Step 1: C = 100 + 0.75(400) = 100 + 300 = 400. (1 mark)
Step 2: MPC = 0.75 (the slope); autonomous consumption = 100 (intercept). (1 mark)
Step 3: APC = C ÷ Y = 400 ÷ 400 = 1.0 (all income consumed; saving = 0 here). (1 mark)

Worked Example 8.3 — Deflationary Gap (3 marks)

Full-employment output Y* = 1,000. Current AD gives equilibrium Y = 900.
Step 1: Deflationary gap = Y* − Y = 100 (output shortfall, unemployment exists). (1 mark)
Step 2: Policy: expansionary fiscal (↑G or ↓T) to shift AD right. (1 mark)
Step 3: Required ΔG ≈ gap ÷ k; if k = 5, ΔG = 20 lifts Y by 100 to full employment. (1 mark)

Worked Example 8.4 — Open-Economy Multiplier (3 marks)

MPC = 0.8, marginal tax rate t = 0.2, marginal propensity to import m = 0.1.
Step 1: Leakages per dollar = MPS + t + m = 0.2 + 0.2 + 0.1 = 0.5. (1 mark)
Step 2: Open multiplier k = 1 ÷ (MPS + t + m) = 1 ÷ 0.5 = 2. (1 mark)
Step 3: Smaller than closed-economy k = 5 because taxes and imports drain the circular flow. (1 mark)

Worked Example 8.5 — Inflationary Gap (3 marks)

Full-employment Y* = 1,000. Expansionary shock pushes AD equilibrium to Y = 1,050.
Step 1: Inflationary gap = 1,050 − 1,000 = 50 (demand exceeds capacity → demand-pull inflation). (1 mark)
Step 2: Policy: contractionary fiscal (↓G or ↑T) to shift AD left. (1 mark)
Step 3: In the long run, rising prices self-correct real output back toward Y* (along LRAS). (1 mark)

Common Trap：k = 1 ÷ (1 − MPC) assumes no imports and no taxes leaking from the circular flow. In an open economy with proportional taxes and imports, the true multiplier is smaller. Also, MPC + MPS = 1 must always hold; if a question gives both, check they sum to 1 before calculating. 另：deflationary gap 对应的是"失业/产出不足"，要用扩张政策；很多考生把 gap 方向搞反，写成紧缩，整题丢分。

练习题库 Economics 卷见 /question-bank/economics/（G 单元乘数计算题）。

Unit 9 Money and Banking ★★★

本单元 Command Word 答题模板

Command Word	一-line 规则	本单元示例
State	仅1句官方定义，无需解释	Define money. → "Money is anything generally accepted as a medium of exchange."
Describe	趋势 + 对应图表数据引用	Describe credit creation. → "With rrr 20%, an initial $100 becomes $500 total deposits."
Explain	定义 + 因果推导（必须使用 because 逻辑链）	Explain how credit is created. → "Credit is created because banks lend a fraction of deposits, which become new deposits elsewhere, multiplying supply."
Discuss	正方论点 + 反方论点，无主观判断	Discuss the Linked Exchange Rate. → "For: anchors inflation expectations; against: removes independent monetary policy."
Evaluate	正反分析 + 个人合理评判（高分必备）	Evaluate fractional-reserve banking. → "It creates liquidity but risks runs; on balance needs regulation and deposit insurance."

Term	Official English Definition	中文注解
Money	Anything generally accepted as a medium of exchange	货币的核心定义
Functions of money	Medium of exchange / Unit of account / Store of value / Standard of deferred payment	四大功能全背
M1 / M2 / M3 (HK)	M1 = 流通现金+活期存款；M2 = M1+储蓄及定期存款+NCD 等	香港货币供应定义
Credit creation	Banking system creates deposits through fractional reserve lending	存款创造
Maximum money supply change	ΔDeposits = Initial deposit × 1/required reserve ratio	货币乘数计算
Linked Exchange Rate System	HKD pegged to USD at 7.75–7.85 under a currency board system	香港联系汇率制度

本单元必背官方定义（默写用）

① HKEAA Official Definition（一字不改原版英文）

Money is anything generally accepted as a medium of exchange.

② Exam Short Answer Sentence（2分简答默写短句，附中文注解）

简答默写："Money serves as a medium of exchange, unit of account, store of value and standard of deferred payment."（货币四大功能：交易媒介、计价单位、价值储存、延期支付标准。）

① HKEAA Official Definition（一字不改原版英文）

The Linked Exchange Rate System pegs the HKD to the USD at 7.75–7.85 under a currency board system.

② Exam Short Answer Sentence（2分简答默写短句，附中文注解）

简答默写："Under the currency board, the HKMA cannot set interest rates independently, so HK has no independent monetary policy."（联系汇率下香港无独立货币政策，利率跟随美国。）

How it works 核心机理

Under fractional-reserve banking, a bank keeps only a fraction of deposits as reserves and lends out the rest. 银行只留一部分存款作准备金，其余贷出。The borrower's loan becomes another bank's deposit, which is again partly lent out — this chain multiplies the initial deposit into a much larger total money supply. 借款人把贷款存入别家银行，别家再贷出，层层创造存款。The simpler the reserve rule (no cash drain), the bigger the multiplier. 若公众不把新存款提现（无现金漏损），乘数 = 1 ÷ rrr；若公众按比率 c 持有现金，乘数 = 1 ÷ (rrr + c)，漏损会显著缩小乘数。香港的联系汇率是 currency board：发钞银行须按 7.80 固定汇率交美元才可发港币，故 HKMA 无独立货币政策，利率跟随美国。

Worked Example 9.1 — Money Multiplier with Cash Drain (4 marks)

Initial deposit = $1,000. Required reserve ratio = 10%. The public keeps 20% of any new deposit as cash (currency drain ratio c = 0.2).

Step 1: Money multiplier m = 1 ÷ (rrr + c) = 1 ÷ (0.10 + 0.20) = 1 ÷ 0.30. (1 mark)
Step 2: m = 3.33 (or 10/3). (1 mark)
Step 3: Maximum money supply change = 1,000 × 3.33 = $3,333. (1 mark)
Step 4: Compare: with NO cash drain, m = 1 ÷ 0.10 = 10, change = $10,000. Cash drain sharply reduces the multiplier. (1 mark)

Worked Example 9.2 — Basic Multiplier (No Drain) (3 marks)

Initial cash deposit = $500. Required reserve ratio = 25%.
Step 1: With no cash drain, m = 1 ÷ rrr = 1 ÷ 0.25 = 4. (1 mark)
Step 2: Max deposit creation = 500 × 4 = $2,000 total deposits (including the initial). (1 mark)
Step 3: New money created (excluding initial) = 2,000 − 500 = $1,500. Distinguish total from increment. (1 mark)

Worked Example 9.3 — Step-by-Step Credit Creation (4 marks)

Bank A gets $100 deposit, rrr = 20%.
Step 1: A keeps $20 reserve, lends $80. (1 mark)
Step 2: $80 deposited in Bank B; B keeps $16, lends $64. (1 mark)
Step 3: Process continues; total = 100 + 80 + 64 + ... = 100 × (1/0.2) = $500. (1 mark)
Step 4: Each bank lends (1 − rrr) of its deposit; the geometric series sums to initial × 1/rrr. (1 mark)

Worked Example 9.4 — M1 vs M2 (2 marks)

HK figures: cash $200bn, demand deposits $800bn, time/savings deposits $3,000bn.
Step 1: M1 = cash + demand deposits = 200 + 800 = $1,000bn. (1 mark)
Step 2: M2 = M1 + time/savings + NCD ≈ 1,000 + 3,000 = $4,000bn (M2 > M1, broader measure). (1 mark)

Worked Example 9.5 — Linked Exchange Rate (3 marks)

The HKD/USD peg is 7.80, band 7.75–7.85, operated as a currency board.
Step 1: To issue HKD, the monetary authority must hold equivalent USD reserves at 7.80. (1 mark)
Step 2: HKMA cannot set interest rates independently; HK rates track US Fed funds. (1 mark)
Step 3: Implication: Hong Kong has NO independent monetary policy; stabilisation relies on fiscal policy. (1 mark)

Common Trap：Use the right multiplier formula. If the public holds NO extra cash (fixed cash), multiplier = 1 ÷ rrr. If the public holds a fraction of new deposits as cash, multiplier = 1 ÷ (rrr + c). Mixing them up is the single most common money-creation error. 另：分清"总存款"与"新增货币"——题目问 Δmoney supply 时通常指新增部分，别把初始存款也算成"创造"。

练习题库 Economics 卷见 /question-bank/economics/（H 单元存款创造计算）。

Unit 10 Inflation, Deflation and Unemployment ★★★

💡 写 DRQ 前先回看本单元 Command Word 模板与上方 DRQ 强制提醒。

本单元 Command Word 答题模板

Command Word	一-line 规则	本单元示例
State	仅1句官方定义，无需解释	Define inflation. → "Inflation is a sustained increase in the general price level."
Describe	趋势 + 对应图表数据引用	Describe CPI-based inflation. → "CPI 120 → 126 gives an inflation rate of 5%."
Explain	定义 + 因果推导（必须使用 because 逻辑链）	Explain why borrowers gain from inflation. → "Borrowers gain because they repay with money of lower purchasing power, so real debt falls."
Discuss	正方论点 + 反方论点，无主观判断	Discuss inflation's distributional effects. → "For: helps debtors and asset holders; against: hurts lenders and cash holders."
Evaluate	正反分析 + 个人合理评判（高分必备）	Evaluate moderate inflation. → "Moderate inflation aids adjustment but high inflation distorts; on balance low stable inflation is preferable."

Term	Official English Definition	中文注解
Inflation	A sustained increase in the general price level	持续+整体物价，两词缺一不可
CPI	Measures changes in the price level of a basket of consumer goods	消费物价指数
Inflation rate	(CPI₁ − CPI₀) ÷ CPI₀ × 100%	通胀率公式
Unemployment rate	Unemployed ÷ labour force × 100%（不是除以总人口！）	失业率
Labour force participation rate	Labour force ÷ population aged 15+ × 100%	劳动人口参与率
Frictional / Structural / Cyclical unemployment	摩擦性（换工过渡）/ 结构性（技能错配）/ 周期性（需求不足）	三类失业成因不同

通胀赢家输家（Discuss 常考）：债务人（固定利率）赢、债权人输；持实物资产者赢、持现金者输。

本单元必背官方定义（默写用）

① HKEAA Official Definition（一字不改原版英文）

Inflation is a sustained increase in the general price level.

② Exam Short Answer Sentence（2分简答默写短句，附中文注解）

简答默写："Inflation is a sustained, general rise in the price level; a one-month or single-good rise is not inflation."（通胀须为"持续+整体"物价上升。）

① HKEAA Official Definition（一字不改原版英文）

The unemployment rate = unemployed ÷ labour force × 100%.

② Exam Short Answer Sentence（2分简答默写短句，附中文注解）

简答默写："The unemployment rate divides the unemployed by the labour force (employed + unemployed), not by total population."（失业率分母用劳动人口，非总人口。）

How it works 核心机理

The unemployment rate divides the UNEMPLOYED by the LABOUR FORCE (employed + unemployed), not by total population. 失业率是"失业者 ÷ 劳动人口"，劳动人口 = 就业 + 失业，不含小孩、退休者、放弃求职者。Inflation redistributes wealth because nominal debts are fixed while the real value of money falls — borrowers repay with cheaper dollars, so they gain and lenders lose. 通胀使名义债务不变、货币购买力降，债务人用"较便宜的钱"还债而得益，债权人受损。CPI 追踪一篮子消费品价格，通胀率 = (CPI₁ − CPI₀) ÷ CPI₀ × 100%。三类失业中，cyclical 与总需求不足相关、可用需求政策处理；structural 需再培训；frictional 是过渡性、难以消除。

Worked Example 10.1 — Unemployment Rate (3 marks)

Population aged 15+ = 1,000,000. Employed = 600,000. Unemployed = 100,000. Calculate the unemployment rate and the labour force participation rate.

Step 1: Labour force = employed + unemployed = 600,000 + 100,000 = 700,000. (1 mark)
Step 2: Unemployment rate = 100,000 ÷ 700,000 × 100% = 14.3%. (1 mark)
Step 3: Participation rate = 700,000 ÷ 1,000,000 × 100% = 70%. (1 mark)

Worked Example 10.2 — Inflation Rate from CPI (3 marks)

CPI was 120 last year, 126 this year.
Step 1: Inflation rate = (126 − 120) ÷ 120 × 100%. (1 mark)
Step 2: = 6 ÷ 120 × 100% = 5%. (1 mark)
Step 3: State: "The general price level rose 5% over the year" — sustained rise = inflation. (1 mark)

Worked Example 10.3 — CPI Basket Logic (2 marks)

If the price of housing (weight 30% in basket) rises 10% while electronics (weight 10%) fall 10%, what happens to CPI?
Step 1: CPI is a weighted average; housing's larger weight dominates. (1 mark)
Step 2: Net CPI rises (roughly +0.3×10 − 0.1×10 = +2%), so inflation positive. (1 mark)

Worked Example 10.4 — Types of Unemployment (3 marks)

(a) A factory closes as its product becomes obsolete. (b) A worker searches between jobs. (c) Recession cuts demand.
Step 1: (a) STRUCTURAL — skills/industry mismatch, needs retraining. (1 mark)
Step 2: (b) FRICTIONAL — normal job transition, short-term. (1 mark)
Step 3: (c) CYCLICAL — tied to low AD, cured by expansionary demand policy. (1 mark)

Worked Example 10.5 — Winners and Losers of Inflation (3 marks)

Unexpected 8% inflation occurs; a borrower owes $10,000 fixed at 5% nominal interest.
Step 1: Borrower repays in dollars worth 8% less in real terms → real burden falls, borrower WINS. (1 mark)
Step 2: Lender receives repayments whose purchasing power dropped → lender LOSES. (1 mark)
Step 3: Holder of real assets (property, gold) keeps value → wins; holder of cash loses purchasing power. (1 mark)

Common Trap：Children, retirees, and discouraged workers who stopped searching are NOT in the labour force, so they are NOT counted as unemployed. Dividing unemployment by total population (instead of the labour force) is the classic mistake that produces a wrong, usually smaller, rate. 另：inflation 必须是"sustained + general"——单月或个别商品价格涨不算通胀；deflation 是持续物价下跌，常伴随需求萎缩。

练习题库 Economics 卷见 /question-bank/economics/（I 单元失业与通胀题）。

Unit 11 Fiscal and Monetary Policy ★★★

💡 写 DRQ 前先回看本单元 Command Word 模板与上方 DRQ 强制提醒。

本单元 Command Word 答题模板

Command Word	一-line 规则	本单元示例
State	仅1句官方定义，无需解释	Define expansionary fiscal policy. → "Expansionary fiscal policy increases government expenditure and/or reduces tax to shift AD right."
Describe	趋势 + 对应图表数据引用	Describe a budget deficit. → "G 300 > T 250 gives a budget deficit of $50bn."
Explain	定义 + 因果推导（必须使用 because 逻辑链）	Explain HK's policy constraint. → "HK cannot cut rates independently because the currency board pegs HKD to USD, so rates track the US Fed."
Discuss	正方论点 + 反方论点，无主观判断	Discuss automatic stabilisers. → "For: smooth fluctuations without new laws; against: may slow recovery if too generous."
Evaluate	正反分析 + 个人合理评判（高分必备）	Evaluate fiscal vs monetary in HK. → "Fiscal dominates in HK due to the peg; on balance HK must rely on fiscal and structural measures."

• Expansionary fiscal policy：increase government expenditure and/or reduce tax → AD 右移
• 香港特殊性：联系汇率下 香港没有独立货币政策（Discuss 题高频考点）
• Budget surplus/deficit/balanced 定义与判断
• Contractionary fiscal：decrease G and/or increase T → AD 左移
• Monetary policy tools：reserve requirement / discount rate / open market operations（一般经济体）
• Automatic stabilisers：progressive tax and welfare benefits that dampen fluctuations without new laws

本单元必背官方定义（默写用）

① HKEAA Official Definition（一字不改原版英文）

Expansionary fiscal policy increases government expenditure and/or reduces tax to shift AD rightward.

② Exam Short Answer Sentence（2分简答默写短句，附中文注解）

简答默写："An increase in G or a cut in T raises disposable income, so C and AD rise, closing a deflationary gap."（扩张财政：增开支或减税→AD 右移→填 deflationary gap。）

How it works 核心机理

Expansionary fiscal policy (raise G and/or cut T) increases AD, raising both output and the price level — used to close a deflationary gap. 扩大政府开支或减税→可支配收入升→C 升→AD 右移→产出与物价齐升，用来填 deflationary gap。Because Hong Kong runs a currency board, the HKMA cannot set an independent interest rate; it follows the US Fed, so Hong Kong's main stabilisation tool is fiscal policy, not monetary policy. 香港因 currency board 无法独立定息，所以主要稳经工具是财政而非货币。在一般经济体，monetary policy 透过降低利率刺激投资；但香港此路不通。Automatic stabilisers（累进税、福利）在衰退时自动减税增支，无需新立法即缓冲波动。

Worked Example 11.1 — Budget Balance (3 marks)

Government expenditure G = $300bn. Tax revenue T = $250bn. Is the budget in surplus, deficit, or balance? By how much?

Step 1: Compare G and T: if G > T, deficit; G < T, surplus; G = T, balanced. (1 mark)
Step 2: Here G ($300bn) > T ($250bn), so budget is in DEFICIT. (1 mark)
Step 3: Deficit size = 300 − 250 = $50bn. State: "The government runs a $50bn budget deficit, which is expansionary fiscal policy." (1 mark)

Worked Example 11.2 — Expansionary Fiscal Effect (4 marks)

Economy in deflationary gap. Government raises G by $40bn, MPC = 0.75.
Step 1: k = 1 ÷ (1 − 0.75) = 4. (1 mark)
Step 2: ΔY = 4 × 40 = $160bn increase in national income. (1 mark)
Step 3: AD shifts right; real output rises, unemployment falls. (1 mark)
Step 4: Side effect: if near full employment, the extra AD mainly raises price level (inflation) instead of output. (1 mark)

Worked Example 11.3 — Hong Kong's Policy Constraint (3 marks)

HK faces a recession. Can the HKMA cut interest rates independently to stimulate?
Step 1: No. Under the Linked Exchange Rate (currency board), HK rates track US rates. (1 mark)
Step 2: HK has NO independent monetary policy — cutting rates unilaterally would break the peg. (1 mark)
Step 3: HK must rely on FISCAL policy (G / T) and structural measures to stabilise. (1 mark)

Worked Example 11.4 — Automatic Stabilisers (3 marks)

During a downturn, incomes fall.
Step 1: Progressive income tax automatically collects LESS as incomes fall → disposable income falls less than gross. (1 mark)
Step 2: Unemployment benefits automatically RISE → support demand. (1 mark)
Step 3: These stabilisers cushion the fall in AD without new legislation; contrast with discretionary fiscal policy. (1 mark)

Worked Example 11.5 — Contractionary Policy (3 marks)

Economy has an inflationary gap. Suggest a fiscal response.
Step 1: Use CONTRACTIONARY fiscal: decrease G and/or increase T. (1 mark)
Step 2: This lowers disposable income → C falls → AD shifts left. (1 mark)
Step 3: Result: price level falls toward target, real output returns toward full employment. (1 mark)

Common Trap：A budget deficit is NOT the same as national debt — deficit is the annual gap, debt is the accumulated total. Also, in HKDSE essays, always state that Hong Kong has NO independent monetary policy under the Linked Exchange Rate; suggesting the HKMA can freely cut rates to boost the economy is a wrong, high-penalty claim. 另：fiscal policy 影响 AD 同时影响 price level 与 output——在接近充分就业时，扩张财政主要推高物价而非产出，这一点 essay 常要求点出。

练习题库 Economics 卷见 /question-bank/economics/（I 单元政策分析题）。

Unit 12 International Trade ★★

💡 写 DRQ 前先回看本单元 Command Word 模板与上方 DRQ 强制提醒。

本单元 Command Word 答题模板

Command Word	一-line 规则	本单元示例
State	仅1句官方定义，无需解释	Define comparative advantage. → "A country has a comparative advantage if it can produce a good at a lower opportunity cost than another country."
Describe	趋势 + 对应图表数据引用	Describe gains from trade. → "Specialisation lets both consume beyond the PPC at the world price of 1:1."
Explain	定义 + 因果推导（必须使用 because 逻辑链）	Explain why trade increases welfare. → "Trade raises welfare because each country specialises where its opportunity cost is lowest, raising total output."
Discuss	正方论点 + 反方论点，无主观判断	Discuss protectionism. → "For: protects infant industries and jobs; against: reduces world efficiency and raises prices."
Evaluate	正反分析 + 个人合理评判（高分必备）	Evaluate free trade. → "Free trade maximises world output but harms unprotected sectors; on balance beneficial with adjustment support."

• Absolute vs Comparative advantage：A country has a comparative advantage if it can produce a good at a lower opportunity cost
• 计算比较优势：算各国生产 1 单位 X 的机会成本再比较
• Trade barriers: tariff / quota / subsidy 的图形分析
• Exchange rate：本币贬值 → 出口便宜进口贵 → 净出口↑（条件：需求有弹性）
• Terms of trade：index of export prices ÷ import prices × 100
• Balance of payments：current account + capital/financial account = 0（总体）
• Protectionism arguments：infant industry / employment / strategic / anti-dumping

本单元必背官方定义（默写用）

① HKEAA Official Definition（一字不改原版英文）

A country has a comparative advantage if it can produce a good at a lower opportunity cost than another country.

② Exam Short Answer Sentence（2分简答默写短句，附中文注解）

简答默写："Country A has a comparative advantage in computers because its opportunity cost (0.5 car) is lower than B's (1 car)."（比较优势看机会成本，非绝对产量。）

How it works 核心机理

Comparative advantage is about OPPORTUNITY COST, not absolute productivity. 比较优势看的是"生产一单位的机会成本"而非绝对产量。Even if one country is worse at everything, it should still specialise in the good where its opportunity cost is relatively lowest, then trade — both countries gain from lower world prices and more total output. 即便两国某方样样落后，它也应在"相对机会成本最低"的商品上专精并贸易，双方都因世界价格更优、总产出更大而得益。Trade barriers（tariff/quota/subsidy）扭曲此分工、制造 DWL，但保护主义者以 infant industry、就业、战略为由辩护。汇率贬值令出口相对便宜、进口变贵，净出口上升（前提是进出口需求有弹性），改善 current account。

Worked Example 12.1 — Comparative Advantage (4 marks)

In 1 hour, Country A produces 10 cars OR 20 computers. Country B produces 5 cars OR 5 computers.
(a) Which country has comparative advantage in cars? In computers?

Step 1: A's opp. cost of 1 car = 20 ÷ 10 = 2 computers. B's opp. cost of 1 car = 5 ÷ 5 = 1 computer. (1 mark)
Step 2: B has lower opp. cost in cars → B has comparative advantage in CARS. (1 mark)
Step 3: A's opp. cost of 1 computer = 10 ÷ 20 = 0.5 car. B's opp. cost of 1 computer = 5 ÷ 5 = 1 car. (1 mark)
Step 4: A has lower opp. cost in computers → A has comparative advantage in COMPUTERS. Each country specialises where its opp. cost is lower. (1 mark)

Worked Example 12.2 — Absolute vs Comparative (3 marks)

Country A makes 10 wine & 10 cloth. Country B makes 4 wine & 2 cloth.
Step 1: A is absolutely more efficient in BOTH (10>4, 10>2) → A has absolute advantage in both. (1 mark)
Step 2: A's opp cost of 1 wine = 1 cloth; B's = 2÷4 = 0.5 cloth → B has comparative advantage in WINE. (1 mark)
Step 3: A's opp cost of 1 cloth = 1 wine; B's = 4÷2 = 2 wine → A has comparative advantage in CLOTH. Both still gain from trading. (1 mark)

Worked Example 12.3 — Gains from Trade (3 marks)

World price of computers = 1 car each (between A's 0.5 and B's 1). Both specialise.
Step 1: A makes only computers, B makes only cars; total output rises vs autarky. (1 mark)
Step 2: At world price 1:1, A trades computers for cars cheaper than its domestic 0.5? (verify) → consumes beyond PPC. (1 mark)
Step 3: Both reach a consumption point OUTSIDE their own PPC → mutual gain. (1 mark)

Worked Example 12.4 — Tariff Effect (4 marks)

Small country, free-trade world price Pw = $10, tariff t = $2.
Step 1: Domestic price rises from $10 to Pw + t = $12. (1 mark)
Step 2: Import volume falls (domestic supply up, domestic demand down). (1 mark)
Step 3: Government gains tariff revenue = t × new import quantity (a rectangle). (1 mark)
Step 4: Two DWL triangles appear (production inefficiency + consumption inefficiency); tariff reduces national welfare. (1 mark)

Worked Example 12.5 — Exchange Rate Depreciation (3 marks)

HKD depreciates against USD; HK exports become cheaper in USD terms.
Step 1: Foreign buyers pay less USD for same HK goods → export volume tends to rise. (1 mark)
Step 2: HK imports cost more HKD → import volume tends to fall. (1 mark)
Step 3: Net exports (X − M) rise, improving the current account — provided demand is elastic enough (Marshall–Lerner condition). (1 mark)

Common Trap：Do not use absolute output to decide advantage — that gives absolute, not comparative, advantage and is WRONG for trade-gain questions. Always convert to opportunity cost (what you give up). A country can have a comparative advantage even if it is absolutely less efficient at producing both goods. 另：tariff 与 subsidy 方向不同——tariff 抬高国内价、subsidy 降低国内价（鼓励出口/生产），作图别画反。J 单元 essay 常要求 evaluate 保护主义的利弊，须两面下结论。

练习题库 Economics 卷见 /question-bank/economics/（J 单元比较优势与关税图）。

Command Words 分层高分作答体系（全站置顶）★★★

指令词	满分固定结构	字数/格式要求	硬性扣分红线
State（1-2分定义题）	照搬考评局原版定义句	1 句话，30 词以内	自行改写、删减关键词直接丢全分
Describe（图表/数据题）	整体趋势 + 分段变化 + 数值特征	2-3 句话，带上坐标数值	只写涨跌、不带数据描述，最多拿一半分
Explain（因果分析题）	定义 → 内在运行机制 → 最终结果（必须用 because/therefore 串联逻辑链）	三段式分层书写	缺少定义、逻辑断裂、无因果连接词，采分点对半扣除
Discuss（双边分析）	正方论点+经济原理+案例/数据 → 反方论点+经济原理+案例/数据	两段独立主体段落，无个人立场	只写单面分析直接封顶 2/6 分；使用列表符号扣除全部 2 分 EC 分
Evaluate（高分压轴DRQ必考）	双面均衡分析 + 有理据主观评判 + 评判依据（成本/时效/社会副作用）	四段完整短文，结尾评判必须落地	只有分析无评判、评判无理由，无法拿到 Band 5** 档位分数

全站通用 DRQ 铁律：长篇作答必须段落式行文，禁止数字序号、项目符号、分点罗列，EC 2 分一经违规直接清零——这是绝大多数考生卡在 5* 上不去的首要原因。

DRQ 长题规则：

1. 开头先定义核心术语（定义分白送，必拿）
2. 每段一个论点：Topic sentence → Explanation → Example
3. 禁用 bullet points，必须完整句子成段，否则丢 EC (Effective Communication) 分
4. Evaluate 题结尾必须表态：In conclusion, I agree/disagree that... because the benefits outweigh the costs...

⚠️ DRQ 强制提醒：DRQ 禁止项目符号/列表，必须分段式英文短文，否则 EC 沟通 2 分全扣；每段至少引用题目一组数据支撑观点。

高分作文 Checklist：

• 定义术语是否一字不差（英文）？
• 每段是否有 topic sentence + 因果链 + 例子？
• Diagram 是否标齐四要件（轴、曲线、均衡点、箭头）？
• Evaluate 是否给出明确判断与权衡（balance of costs and benefits）？
• 是否避免了 bullet points、用了连贯英文段落？

Part 3 Current Economic Issues（每月更新）

关注方向：香港本地经济（楼市、旅游、金融中心地位）、内地宏观政策、全球通胀与利率周期、国际贸易格局。建议每月用下方指令让 AI 汇总时事并关联考点。

Act as an HKDSE Economics current-affairs curator. Summarise the 5 most exam-relevant economic events of the past month (Hong Kong & global). For each event: (1) one-paragraph English summary, (2) matched HKDSE syllabus unit, (3) one possible DRQ-style question with a suggested answer outline.

每月可直接默写英文范文（香港宏观议题）

以下三段为考试风英文范文，可整段背诵改写。每段均含至少一个数据锚点，符合 HKEAA 英文表达习惯，适用于 DRQ / Essay 的宏观议题段落。

(a) 通胀与香港物价（Inflation & HK cost of living）

Hong Kong's inflation has remained moderate but the cost of living keeps biting households. In recent years the Composite Consumer Price Index (CCPI) rose by about 2.0% year-on-year, yet housing and food components climbed faster, squeezing low-income families. Inflation is a sustained increase in the general price level; even a small rate erodes the real value of cash savings. The government partly offsets this through the Comprehensive Social Security Assistance and transport subsidies. From a DSE perspective, unexpected inflation redistributes income: borrowers and owners of real assets gain, while lenders and cash holders lose. Discuss questions often ask whether the poor are hurt most — the answer is yes, because they spend a larger share of income on necessities with inelastic demand. Policymakers should therefore target relief at essentials rather than across-the-board handouts.

中文注解：以 CCPI ≈ 2.0% 为数据锚点，串起"通胀定义 → 收入分配效应 → 对低收入家庭冲击"。Discuss 题必须点出 inelastic demand 与 redistribution。

(b) 联系汇率制度（Linked Exchange Rate System, HKD 7.75–7.85）

The Linked Exchange Rate System (LERS) is a currency board that pegs the Hong Kong dollar to the US dollar within a narrow band of 7.75–7.85 per USD. Under this system, note-issuing banks must deposit equivalent US dollars with the Hong Kong Monetary Authority before issuing Hong Kong dollars, which guarantees the peg. Because the HKD is tightly linked to the USD, Hong Kong cannot set interest rates independently; the HKMA's rates track the US Federal Reserve. This anchors inflation expectations and promotes monetary stability, but it means Hong Kong loses an independent monetary policy and must rely on fiscal measures to stabilise the economy. In DRQ essays, candidates must state clearly that Hong Kong has NO independent monetary policy under the currency board; suggesting the HKMA can freely cut rates to boost growth is a high-penalty error.

中文注解：核心数据锚点 7.75–7.85 per USD；必须落到"香港无独立货币政策"，这是 I / J 单元 Discuss / Evaluate 高频得分点。

(c) 楼市政策（Hong Kong housing policy / stamp duty / land supply）

Hong Kong's housing policy aims to improve affordability by managing both demand and supply. On the demand side, the government imposes stamp duties such as the Buyer's Stamp Duty (BSD) and the Additional Stamp Duty (SSD) to deter speculative and non-local purchases, while on the supply side it increases land through reclamation and the Northern Metropolis development. In 2024 the government relaxed some demand-side measures, cutting the BSD rate to 7.5% to revive market sentiment. From an economics view, a stamp duty is a transaction tax that raises the effective cost of buying, reducing quantity traded and creating a deadweight loss, but it can cool an overheated market. Candidates should evaluate both sides: intervention eases affordability yet distorts allocation; on balance, a mix of supply expansion and targeted demand control is preferable to a single tool.

中文注解：数据锚点 BSD 7.5%（2024）；用"交易税 → 有效成本↑ → 交易量↓ → DWL"链条作 Explain，再用 Evaluate 两面收尾。

歷屆真題演練（2024 Live Papers，附評卷參考）

以下題目改編自 HKEAA 2024 公開試，括號內為當屆考生正選率，助你判斷「易錯陷阱」。每題均附模型答案 / Model Answer，列明評分點與推理。

Q1（Paper 1 Q14 · Elasticity & Tax）正選率 35%

When the per-unit sales tax on Good X is halved, the government's tax revenue from Good X is also halved. One possible explanation is that ___.

• A. the supply of Good X is perfectly elastic (9%)
• B. the supply of Good X is perfectly inelastic (32%)
• C. the demand for Good X is perfectly elastic (23%)
• D. the demand for Good X is unitarily elastic (35%) ✅

評卷筆記：Tax revenue = t × Q。t 减半而 TR 也减半 ⟹ Q 不變 ⟹ 需求量對價格完全無彈性變化 ⟹ unitarily elastic (PED = 1)。多數考生誤選 B（以為 supply inelastic 才令 Q 不變），但題目說的是「稅收隨稅率等比變動」，關鍵在 demand 的彈性。

模型答案 / Model Answer：

• 评卷点 1（1 分）：写出税收恒等式 Tax revenue = t × Q，指出 t 减半。
• 评卷点 2（1 分）：TR 也减半 ⟹ Q 必须保持不变（因为 TR 与 t 同向等比）。
• 评卷点 3（1 分）：Q 不随含税价格变动 ⟹ 需求量对价格完全无反应 ⟹ PED 的绝对值为 1（unitary elastic）。
• 评卷点 4（1 分）：排除 B——supply inelastic 只决定税负谁担，不改变"Q 随 t 不变"这一需求侧现象；题干现象由 demand 弹性决定。结论：选 D。

Q2（Paper 1 Q18 · Perfect Competition）正選率 45%

Which of the following statements about perfect competition is INCORRECT?

• A. The market price tends to be stable as no firm can affect the market price. (19%)
• B. Price is the only competitive criterion in determining the distribution of goods. (45%) ✅
• C. The marginal cost of the last unit of all firms is equal when firms maximise profits. (31%)
• D. Firms sell homogeneous products. (5%)

評卷筆記：B 錯——完全競爭下 product 是 homogeneous，競爭準則不止價格（還有 location 等非價格因素的描述在題目語境中為幹擾）。此題考「only」字眼陷阱，選 INCORRECT 時先找絕對詞。

模型答案 / Model Answer：

• 评卷点 1（1 分）：确认 perfect competition 特征：many firms、homogeneous product、price taker、free entry。
• 评卷点 2（1 分）：A 正确——单个 firm 是 price taker，价格稳定。
• 评卷点 3（1 分）：C 正确——利润最大化时每家 P = MC，故最后单位 MC 相等。
• 评卷点 4（1 分）：D 正确——同质产品是定义要素。B 用"only"绝对化，错；选 B。

Q3（Paper 1 Q19 · Overproduction & Market Failure）正選率 43%

Which of the following statements about overproduction is/are correct? (1) Overproduction of a good occurs when there is an excess supply of the good. (2) Overproduction does not occur whenever the market is at equilibrium. (3) When overproduction occurs, the marginal social cost is greater than the marginal social benefit at the last unit.

• A. (2) only (12%)
• B. (3) only (25%)
• C. (2) and (3) only (20%)
• D. (1), (2) and (3) (43%) ✅

評卷筆記：三句皆對。(1) 超額供給=overproduction；(2) 均衡時 MSC=MSB，無 overproduction；(3) overproduction 即最後一單位 MSC > MSB（negative externality 導致）。此為 market failure 章節核心定義題。

模型答案 / Model Answer：

• 评卷点 1（1 分）：(1) 正确——overproduction 即市場产量超过有效产量，表现为 excess supply。
• 评卷点 2（1 分）：(2) 正确——equilibrium 时 MSC = MSB，无 over/under-production。
• 评卷点 3（1 分）：(3) 正确——overproduction 时最后一单位 MSC > MSB（负外部性）。
• 评卷点 4（1 分）：三句皆对，选 D。答题时先逐句用 MSB/MSC 框架判断。

Q4（Paper 1 Q22 · Externalities）正選率 56%

In recent years, more people play videos loudly with smartphones on public transport, disturbing others. Which statements are correct? (1) Total social surplus may decrease if this is banned by the government. (2) Economic efficiency may improve if transport suppliers designate quiet zones. (3) The divergence between private and social costs may decrease if people are fined.

• A. (1) and (2) only (9%)
• B. (1) and (3) only (8%)
• C. (2) and (3) only (56%) ✅
• D. (1), (2) and (3) (27%)

評卷筆記：(1) 錯——禁止擾人行為通常提升社會總剩餘（減少 negative externality），不會 decrease。(2) 對——quiet zone 內部化外部性，提升效率。(3) 對——罰款令 private cost 上升趨近 social cost，divergence 收窄。作答 externalities 題一律先畫 MSC/MSB 與 MPC/MPB 圖。

模型答案 / Model Answer：

• 评卷点 1（1 分）：判定 (1) 错——loud video 是 negative externality，ban 它减少外部成本、提升 social surplus，不会 decrease。
• 评卷点 2（1 分）：判定 (2) 对——quiet zone 将外部性内部化（separate space），提高效率。
• 评卷点 3（1 分）：判定 (3) 对——fine 提高 private cost 向 social cost 靠拢，缩小 MSC 与 MPC 的 divergence。
• 评卷点 4（1 分）：组合为 (2) 和 (3)，选 C。

Q5（Paper 1 Q34 · Money & Banking）計算題

The table shows a banking system balance sheet. Suppose there are excess reserves of $20 million and the public always holds a fixed amount of cash.

Assets ($m)		Liabilities ($m)
Reserves	40	Deposits	100
Loans	60

Given the required reserve ratio is 20%, calculate the maximum increase in money supply after the banking system creates new loans.

答案與評分點：

• Required reserves = 20% × 100 = $20m (1 分)
• Excess reserves = 40 − 20 = $20m (1 分，題目已給)
• Money multiplier = 1 / 0.2 = 5 (1 分)
• Maximum deposit expansion = 20 × 5 = $100m；最大貨幣供應增加 = $100m (2 分，答 $100m new deposits 亦給分)
• 關鍵：public holds fixed cash ⟹ 無现金漏損（currency drain = 0），multiplier 用 1/rrr 而非 1/(rrr+c)。

模型答案 / Model Answer：

• 评卷点 1（1 分）：计算法定准备金 RR = rrr × D = 0.2 × 100 = 20。
• 评卷点 2（1 分）：超额准备金 ER = 总准备金 40 − 20 = 20（题干已提示）。
• 评卷点 3（1 分）：因公众持固定现金（无比率漏损），货币乘数 m = 1/rrr = 1/0.2 = 5。
• 评卷点 4（2 分）：最大货币供应增加 = ER × m = 20 × 5 = 100。完整写出"最大存款创造"概念，给满分。结论：money supply 最多增 $100m。

Q6（Paper 1 Q27 · Monopoly & DWL）正選率 38%

Compared with a perfectly competitive industry, a single-price monopoly ___.

• A. produces more output and charges a lower price (12%)
• B. produces the same output but charges a higher price (20%)
• C. produces less output and charges a higher price, creating a deadweight loss (38%) ✅
• D. produces less output but charges a lower price, eliminating deadweight loss (30%)

評卷筆記：Monopoly restricts output below the competitive level to raise price and maximise profit where MR = MC, not where P = MC. The gap between what consumers would pay (demand) and MC at the restricted output is the deadweight loss. 多數考生誤選 D（以為壟斷者會降價搶市場），但單一定價壟斷者無需降價，產量低於競爭水平、價格高於競爭水平。

模型答案 / Model Answer：

• 评卷点 1（1 分）：完全竞争在 P = MC 处生产 Qc、Pc。
• 评卷点 2（1 分）：垄断者利润最大化于 MR = MC，产量 Qm < Qc。
• 评卷点 3（1 分）：对应价格 Pm > Pc（沿需求曲线，产量低则价高）。
• 评卷点 4（1 分）：Qm 到 Qc 之间需求高于 MC 的三角即 deadweight loss。选 C。

Q7（Paper 1 Q33 · Balance of Payments）正選率 41%

If a country has a persistent current account deficit, it means that ___.

• A. its total exports exceed its total imports (10%)
• B. it is a net borrower from / net debtor to the rest of the world over the period (41%)
• C. its capital and financial account must also be in deficit (15%)
• D. the government budget must be in surplus (34%)

評卷筆記：Current account deficit = imports of goods/services/income > exports ⟹ the country receives less than it pays in current transactions, financing the gap by borrowing or selling assets ⟹ net borrower. By the BOP identity, a current account deficit is matched by a capital/financial account SURPLUS (not deficit), so C 錯。考生常混淆兩個帳戶的配對方向。

模型答案 / Model Answer：

• 评卷点 1（1 分）：current account deficit 指经常账户收 < 支（进口 > 出口）。
• 评卷点 2（1 分）：缺口需融资 ⟹ 向外国借入或出售资产 ⟹ 该期成为 net borrower。
• 评卷点 3（1 分）：BOP 恒等式要求 capital/financial account 出现 SURPLUS 来对冲，故 C 错。
• 评卷点 4（1 分）：A 说反（应是进口>出口）；D 与政府预算无必然联系。选 B。

Q8（Paper 1 Q38 · Expansionary Fiscal Policy）正選率 47%

An economy is in a deflationary gap. Which policy is most appropriate and what is its first-round effect?

• A. Cut government spending; AD shifts left (8%)
• B. Raise taxes; price level falls further (11%)
• C. Increase government spending; AD shifts right, real output rises (47%) ✅
• D. Decrease money supply; unemployment rises (34%)

評卷筆記：Deflationary gap = AD too low, unemployment high. Appropriate response = expansionary fiscal (↑G and/or ↓T) → AD right → real output ↑, employment ↑. 注意香港無獨立貨幣政策，故 D 不適用於 HK。考生誤選 D 是把「緊縮」當「擴張」，方向完全相反。

模型答案 / Model Answer：

• 评卷点 1（1 分）：deflationary gap 定义——AD 不足，实际产出 < 潜在，失业高。
• 评卷点 2（1 分）：应采 expansionary fiscal：↑G 或 ↓T，使可支配收入/投资上升。
• 评卷点 3（1 分）：AD 右移，短期 real output 上升、employment 上升。
• 评卷点 4（1 分）：A、B 是收缩方向，D 属货币政策且（在 HK）不可独立使用。选 C。

Q9（Paper 1 Q44 · Tariff）正選率 33%

A small country imposes a tariff on imported Good Z. Compared with free trade, the tariff will ___.

• A. lower the domestic price and increase imports (14%)
• B. raise the domestic price, reduce imports, and create government tariff revenue plus a deadweight loss (33%) ✅
• C. eliminate the deadweight loss of trade (21%)
• D. benefit foreign producers at the expense of domestic consumers (32%)

評卷筆記：Tariff = tax on imports ⟹ domestic price rises to world price + tariff, quantity of imports falls, government collects tariff revenue, and two small DWL triangles appear (production + consumption inefficiency). B 正確。考生常誤以為關稅令國內價格下降（混淆 subsidy 與 tariff 的方向）。

模型答案 / Model Answer：

• 评卷点 1（1 分）：tariff 是对进口征税，国内价从 Pw 升至 Pw + t。
• 评卷点 2（1 分）：国内价升 ⟹ 国内需求降、国内供给升 ⟹ 进口量收缩。
• 评卷点 3（1 分）：政府获得 tariff revenue（矩形 = t × 新进口量）。
• 评卷点 4（1 分）：出现两个 DWL 三角（生产无效率 + 消费无效率），国家福利净损。选 B。

Q10（Paper 1 改编 · Opportunity Cost）正選率约 48%

A student with one free evening can (i) work a shift earning $120, (ii) attend a concert she values at $90, or (iii) prepare for an exam she values at $70. She chooses the exam preparation. Which is the opportunity cost of her choice?

• A. $120 (the shift) (48%)
• B. $90 (the concert) (30%)
• C. $70 (exam prep itself) (12%)
• D. $120 + $90 (both forgone) (10%)

模型答案 / Model Answer：

• 评卷点 1（1 分）：opportunity cost = the single highest-valued option forgone。
• 评卷点 2（1 分）：forgone 选项是 shift ($120) 与 concert ($90)，exam prep 是所选、不算。
• 评卷点 3（1 分）：最高价值是 $120（shift），故选 A。
• 评卷点 4（1 分）：排除 D（不能加总所有放弃项）、C（不能是自己选的）。标准答法："The opportunity cost is the highest-valued alternative forgone, $120."

Q11（Paper 1 改编 · Real vs Nominal GDP）正選率约 52%

Country X's nominal GDP rose 8% but its GDP deflator rose 8% over the year. Which is correct?

• A. Real GDP rose 8% (20%)
• B. Real GDP was unchanged (52%)
• C. Living standard must have risen (15%)
• D. The country had deflation (13%)

模型答案 / Model Answer：

• 评卷点 1（1 分）：Real GDP 增长率 ≈ Nominal 增长率 − 通胀率（deflator 升幅）。
• 评卷点 2（1 分）：8% − 8% = 0% ⟹ real GDP 不变。选 B。
• 评卷点 3（1 分）：A 错把名义当实质；C 错（实质未增，生活水平代理未升）；D 错（deflator 升是通胀非通缩）。
• 评卷点 4（1 分）：强调题目问"living standards"必须看 real GDP，这是高频陷阱。

Q12（Paper 1 改编 · Unemployment Rate）正選率约 44%

In Country Y, population 15+ = 50m, employed = 30m, unemployed = 5m. What is the unemployment rate?

• A. 10% (5 ÷ 50) (33%)
• B. 14.3% (5 ÷ 35) (44%) ✅
• C. 16.7% (5 ÷ 30) (15%)
• D. 85.7% (30 ÷ 35) (8%)

模型答案 / Model Answer：

• 评卷点 1（1 分）：labour force = employed + unemployed = 30 + 5 = 35m。
• 评卷点 2（1 分）：unemployment rate = unemployed ÷ labour force = 5 ÷ 35 = 14.3%。
• 评卷点 3（1 分）：A 错在除以总人口；C 错在除以就业者；D 是就业率非失业率。选 B。
• 评卷点 4（1 分）：再次强调分母是 labour force 不是 population。

Q13（Paper 1 改编 · Multiplier）正選率约 40%

MPC = 0.9, the government cuts taxes by $20bn. Ignoring imports and taxes leakage, the maximum effect on national income is:

• A. $18bn (10%)
• B. $200bn (40%)
• C. $22bn (20%)
• D. $180bn (30%)

模型答案 / Model Answer：

• 评卷点 1（1 分）：tax cut 先增加可支配收入，消费增量 = ΔT × MPC = 20 × 0.9 = 18（初始注入到 C）。
• 评卷点 2（1 分）：multiplier k = 1 ÷ (1 − 0.9) = 10。
• 评卷点 3（1 分）：ΔY = k × (ΔT × MPC) = 10 × 18 = 180，或直接 ΔY = −ΔT × MPC/(1−MPC) = 20 × 0.9/0.1 = 180。选 D。
• 评卷点 4（1 分）：B 是误把 $20 当 ΔG 直接乘 10（税减的注入要先乘 MPC）；A 只算首轮。

Q14（Paper 1 改编 · Comparative Advantage）正選率约 50%

In one day, Country P makes 6 wheat or 3 cloth; Country Q makes 4 wheat or 4 cloth. Which has comparative advantage in cloth?

• A. P (wheat opp cost of cloth = 2 wheat; Q = 1 wheat → Q lower) 选 Q
• B. Q (50%)
• C. Neither (20%)
• D. Both (10%)

模型答案 / Model Answer：

• 评卷点 1（1 分）：P 生产 1 单位 cloth 的机会成本 = 6÷3 = 2 wheat。
• 评卷点 2（1 分）：Q 生产 1 单位 cloth 的机会成本 = 4÷4 = 1 wheat。
• 评卷点 3（1 分）：Q 的机会成本较低 ⟹ Q 在 cloth 有比较优势。选 B（Q）。
• 评卷点 4（1 分）：P 在 wheat 有机会成本 3÷6 = 0.5 cloth，低于 Q 的 4÷4 = 1，故 P 专精 wheat。强调用机会成本而非绝对产量。

Q15（Paper 1 改编 · Phillips Curve）正選率约 46%

According to the long-run Phillips curve, a sustained increase in aggregate demand will:

• A. permanently lower unemployment below the natural rate (18%)
• B. lower unemployment but raise inflation permanently along a stable trade-off (20%)
• C. raise inflation but leave unemployment at the natural rate in the long run (46%) ✅
• D. have no effect on either inflation or unemployment (16%)

模型答案 / Model Answer：

• 评卷点 1（1 分）：short run 存在 inflation–unemployment 取舍（SRPC 右下）。
• 评卷点 2（1 分）：长期 LRPC 垂直在自然失业率处——需求政策只推高通胀，无法永久压低失业。
• 评卷点 3（1 分）：持续 AD 增加 ⟹ 长期失业回到 natural rate，通胀更高。选 C。
• 评卷点 4（1 分）：A 错在"永久"；B 错在把短期取舍当长期；D 忽略短期通胀效应。

Key Diagrams Quick Reference（必画图速查）★★★

以下 8 张图是 DSE 卷二（Short Q / Essay / DRQ）最高频的作图对象。考前必须能手绘并标齐四要件：轴标签、曲线标签、均衡点投影虚线、移动箭头。每图下方附文字走查（Textual Walkthrough），照念即可得分。

作图评分 Checklist（每图必查，缺一项扣 1 分）：① 坐标轴英文标注（如 Price / Quantity）② 曲线名称（如 D₀, S₀, AD, LRAS）③ 均衡点标记（E₀ 及 P₀、Q₀ 投影虚线）。

1. Demand–Supply Shift（供需移动）

• 轴：纵轴 Price ($)，横轴 Quantity
• 曲线：D₀, S₀；移动后 D₁ / S₁
• 移动方向：non-price factor 令 D 或 S 整条右移（增加）或左移（减少）
• 结论句式：The [event] → demand/supply shifts [right/left] → equilibrium price [rises/falls] from P₀ to P₁, equilibrium quantity [rises/falls] from Q₀ to Q₁.

文字走查 / Textual Walkthrough：

• 第一步：先画纵轴 Price、横轴 Quantity，标单位（$ / units）。
• 第二步：画初始 D₀ 与 S₀ 相交于 E₀，向两轴投虚线得 P₀、Q₀。
• 第三步：题目若说"收入上升 / 替代品涨价 / 偏好增强"→ D₀ 整条右移到 D₁；若说"成本下降 / 技术提升 / 减税"→ S₀ 右移到 S₁。务必整条移，不是沿线动。
• 第四步：新交点 E₁，投虚线得 P₁、Q₁。读图：右移需求→P 与 Q 同升；右移供给→P 降 Q 升；左移则反向。
• 结论范式：The increase in [factor] increases demand, shifting D₀ rightward to D₁; equilibrium price rises from P₀ to P₁ and equilibrium quantity rises from Q₀ to Q₁.

本图评分 Checklist（缺一项扣 1 分）：① 坐标轴英文标注（Price / Quantity）② 曲线名称（D₀, D₁, S₀, S₁）③ 均衡点标记（E₀ 及 P₀、Q₀ 投影虚线）。

2. Price Ceiling / Price Floor（价格管制）

• 轴：Price, Quantity
• 曲线：D, S；均衡点 E₀ (P*, Q*)
• 移动方向：ceiling 画在 P* 下方 → Qd > Qs → shortage（短缺）；floor 画在 P* 上方 → Qs > Qd → surplus（过剩）
• 结论句式：An effective price ceiling below equilibrium creates excess demand of (Qd − Qs); an effective price floor creates excess supply of (Qs − Qd).

文字走查 / Textual Walkthrough：

• 第一步：画 D、S 交于 E₀，定均衡价 P*、量 Q*。
• 第二步（ceiling）：在 P* 下方画一条水平线 Pc，标注 "price ceiling (effective)"。在 Pc 高度读图：Qs 在供给曲线左端（小），Qd 在需求曲线右端（大）。
• 第三步：因为 Pc < P* 且具约束力，Qd > Qs，短缺 = Qd − Qs，实际交易量 = Qs（受供给限制）。
• 第四步（floor）：在 P* 上方画水平线 Pf，标注 "price floor (effective)"。Pf 高度 Qs > Qd，过剩 = Qs − Qd，实际交易 = Qd。
• 结论范式：An effective price ceiling set at Pc below P* leads to excess demand of (Qd − Qs); an effective price floor set at Pf above P* leads to excess supply of (Qs − Qd). 注意：若画线在 P* 同侧但不越界则为非约束性（no effect）。

本图评分 Checklist（缺一项扣 1 分）：① 坐标轴英文标注（Price / Quantity）② 曲线名称（D, S, ceiling/floor 水平线）③ 均衡点标记（E₀ 及 P*、Q*；短缺/过剩差额标注）。

3. Tax Incidence（税负分摊）

• 轴：纵轴 Price（买家付 Pb、卖家收 Ps），横轴 Quantity
• 曲线：original S, shifted S+tax；wedge = tax per unit
• 移动方向：S 左移 by the tax amount；买家付 Pb、卖家收 Ps，gap = tax
• 结论句式：The side with the more inelastic curve bears the larger share of the tax; incidence depends on relative elasticities, not on who is legally taxed.

文字走查 / Textual Walkthrough：

• 第一步：画 D 与原始 S₀ 交于 E₀ (P₀, Q₀)。
• 第二步：对卖家征税令供给曲线垂直上移 tax 额至 S₁（新曲线与旧曲线垂直距离 = t）。新交点 E₁ 对应数量 Q₁ < Q₀。
• 第三步：在 Q₁ 垂直高度读两曲线：买家面对的需求价 Pb（在 D 上）；卖家收到的净价 Ps（在 S₀ 上）。Pb − Ps = t = 税负楔子。
• 第四步：比较 burden：buyer burden = Pb − P₀；seller burden = P₀ − Ps。哪边曲线更陡（更 inelastic）哪边负担大。
• 结论范式：Tax incidence is determined by relative elasticities; the more inelastic side bears a larger share of the tax wedge, regardless of who is legally liable.

本图评分 Checklist（缺一项扣 1 分）：① 坐标轴英文标注（Price 纵轴含 Pb/Ps, Quantity 横轴）② 曲线名称（D, S₀, S₁ = S+tax）③ 均衡点标记（E₀ 及 P₀、Q₀；E₁ 与 Pb/Ps 标注）。

4. Monopoly vs Perfect Competition（垄断图）

• 轴：Price, Quantity
• 曲线：D = AR, MR (below AR), MC, AC
• 移动方向：monopoly 在 MR = MC 处产量 Qm < competitive Qc，价格 Pm > Pc
• 结论句式：A single-price monopoly restricts output to Qm and charges Pm > MC, creating a deadweight loss triangle between D and MC from Qm to Qc.

文字走查 / Textual Walkthrough：

• 第一步：画 D (=AR) 向下斜，MR 在 AR 下方、更陡；画 MC 上斜、AC 碗形。
• 第二步（竞争）：完全竞争在 P = MC 处生产 Qc、定价 Pc。
• 第三步（垄断）：垄断者按 MR = MC 定产量 Qm（Qm < Qc），沿 D 曲线找对应价 Pm（Pm > Pc，且 Pm > MC）。
• 第四步：deadweight loss 是从 Qm 到 Qc 之间、需求曲线 D 与 MC 曲线围成的三角——这部分产量社会愿付高于边际成本却未被生产。
• 结论范式：Compared with perfect competition, a single-price monopoly produces less (Qm < Qc) and charges more (Pm > Pc), generating a deadweight loss equal to the triangle between D and MC from Qm to Qc.

本图评分 Checklist（缺一项扣 1 分）：① 坐标轴英文标注（Price / Quantity）② 曲线名称（D=AR, MR, MC, AC）③ 均衡点标记（Qc/Pc 与 Qm/Pm；DWL 三角区）。

5. AD–AS（宏观经济核心图）

• 轴：纵轴 Price Level (or GPL)，横轴 Real GDP / Output
• 曲线：AD (右下)，SRAS (右上)，LRAS (垂直)
• 移动方向：expansionary policy → AD 右移 → real GDP↑, price level↑；supply shock → SRAS 左移 → stagflation
• 结论句式：An increase in AD shifts the AD curve rightward, raising both real output and the price level in the short run; long-run self-correction moves the economy back along LRAS.

文字走查 / Textual Walkthrough：

• 第一步：画纵轴 Price Level、横轴 Real GDP；画 AD（右下）、SRAS（右上）、LRAS（垂直在潜在产出 Y*）。
• 第二步：初始三曲线交于 E₀（短期与长期重合），得 P₀、Y*。
• 第三步（扩张）：AD 右移到 AD₁，与 SRAS 交于 E₁：Real GDP 暂时 > Y*（Y₁ > Y*），Price Level 升至 P₁（需求拉动通胀）。
• 第四步（长期）：高物价使短期预期调整，SRAS 左移到 SRAS₁，回到 LRAS 上的 E₂：产出回到 Y*，物价更高（P₂）。若出现 negative supply shock（如油价升），SRAS 直接左移造成 stagflation（产出降、物价升）。
• 结论范式：An increase in AD shifts AD rightward, raising real output and the price level in the short run; in the long run, the economy self-corrects along the vertical LRAS, returning output to Y* with a higher price level.

本图评分 Checklist（缺一项扣 1 分）：① 坐标轴英文标注（Price Level 纵轴, Real GDP 横轴）② 曲线名称（AD, SRAS, LRAS 垂直）③ 均衡点标记（E₀, E₁ 及 Y*, P₀/P₁ 投影）。

6. Phillips Curve（菲利普斯曲线）

• 轴：纵轴 Inflation Rate，横轴 Unemployment Rate
• 曲线：short-run PC (右下, 可移动)，long-run PC (垂直 at natural rate)
• 移动方向：supply shock / expectation change → SRPC 移动
• 结论句式：There is a short-run trade-off between inflation and unemployment; in the long run the Phillips curve is vertical at the natural rate, so demand policies only shift inflation, not permanent unemployment.

文字走查 / Textual Walkthrough：

• 第一步：画纵轴 Inflation Rate、横轴 Unemployment Rate。
• 第二步：画短期 SRPC 向右下倾斜（通胀高则失业低），标 natural rate of unemployment (u*) 处画长期 LRPC 垂直线。
• 第三步：扩张性需求政策沿 SRPC 向左上移动（失业降、通胀升）到新点；但只是短期。
• 第四步：若通胀预期上升，整条 SRPC 右上移，在同一失业率下通胀更高；长期仍被 LRPC 拉回 u*。
• 结论范式：In the short run there is a trade-off between inflation and unemployment; in the long run the Phillips curve is vertical at the natural rate, so demand management can change inflation but not permanently reduce unemployment.

本图评分 Checklist（缺一项扣 1 分）：① 坐标轴英文标注（Inflation Rate 纵轴, Unemployment Rate 横轴）② 曲线名称（SRPC 右下, LRPC 垂直于 u*）③ 均衡点标记（u* 处 LRPC；SRPC 上移动点）。

7. Comparative Advantage PPC（生产可能性曲线）

• 轴：横轴 Good X，纵轴 Good Y
• 曲线：两国 PPC（斜率 = opp. cost）；trade line (world price) steeper/flatter than domestic
• 移动方向：specialisation → 生产点沿 PPC 移到一端；消费点超出 PPC 靠 trade
• 结论句式：Each country specialises in the good with lower opportunity cost; trade allows consumption beyond the PPC, so both gain.

文字走查 / Textual Walkthrough：

• 第一步：画两国 PPC（通常为直线，斜率绝对值 = 机会成本）。A 国 PPC 线较平（opp cost of X 低），B 国较陡。
• 第二步：无贸易时，各国在 PPC 上某点生产并消费（生产点=消费点）。
• 第三步：specialisation——A 专精 X（生产点移到 X 轴端点），B 专精 Y（移到 Y 轴端点），总产出超 autarky。
• 第四步：画贸易条件线（world price line）比两国国内斜率更优，消费点落在 PPC 之外、贸易线上，双方都获得 PPC 之外的消费组合。
• 结论范式：Each country specialises in the good for which it has the lower opportunity cost; through trade at the world price, both countries can consume at a point outside their own PPC, so both gain.

本图评分 Checklist（缺一项扣 1 分）：① 坐标轴英文标注（Good X 横轴, Good Y 纵轴）② 曲线名称（两国 PPC 直线, world price line）③ 均衡点标记（生产点沿 PPC 端点；消费点落 PPC 外）。

8. Tariff Diagram（关税图）

• 轴：Price, Quantity；world price Pw, domestic supply/demand
• 曲线：Domestic S, D；tariff 后国内价 = Pw + t
• 移动方向：进口量从 (Qd − Qs at Pw) 收缩到 (Qd' − Qs' at Pw+t)；政府收税区 = rectangle
• 结论句式：A tariff raises the domestic price to Pw + t, reduces import volume, yields government revenue, and creates two deadweight loss triangles (production & consumption inefficiency).

文字走查 / Textual Walkthrough：

• 第一步：画 Domestic D 与 S；在自由贸 world price Pw 处画水平线，读出国内 Qs（供给）与 Qd（需求），进口 = Qd − Qs。
• 第二步：征收从价/从量关税 t，国内价升至 Pw + t，画新水平线。
• 第三步：新价下国内 Qs' 上升（本土增产）、Qd' 下降（本土少买），进口收缩为 Qd' − Qs'。
• 第四步：政府税收 = 矩形（宽 = 新进口量，高 = t）；出现两个 DWL 三角：生产三角（本土在高成本多产）＋ 消费三角（消费者少消费）。
• 结论范式：A tariff raises the domestic price to Pw + t, reduces the volume of imports, generates government tariff revenue (the rectangle), and creates two deadweight loss triangles representing production and consumption inefficiency, reducing national welfare.

本图评分 Checklist（缺一项扣 1 分）：① 坐标轴英文标注（Price / Quantity）② 曲线名称（Domestic D, S, world price Pw 水平线）③ 均衡点标记（Pw 与 Pw+t 处 Qs/Qd；tariff revenue 矩形与两个 DWL 三角）。

练习题库 Economics 卷见 /question-bank/economics/（以上各图均有对应作图题）。

经济图表满分采分细则（全章节通用）★★★

标准图表满分 3 项硬性标注，缺一扣 1 分，一张图最多扣 3 分：

1. Horizontal & vertical axis：写明变量名称 + 对应单位（Price: $ / Quantity: units）；
2. Curve formal name：Demand Curve / Supply Curve / AC / MC 不得简写；
3. Equilibrium position：标注均衡价格 Pe、均衡数量 Qe，交点涂黑标识。

高频失分补充：移动曲线必须标注箭头方向；严格区分整条曲线平移（非价格因素）与线上点移动（自身价格），阅卷严格区分二者概念，混用直接判定知识点错误。

易混淆概念全表见独立页面 → 高频易混淆概念对照表（已接入背诵库）。

DRQ 四段式万能高分写作模板 ★★★

Paragraph 1  Opening Definition
Define all core economic terms mentioned in the question precisely with HKEAA official wording.

Paragraph 2  Main supporting analysis
Apply relevant economic theory + draw complete labelled diagram + quote data extracted
directly from the question material to prove the viewpoint.

Paragraph 3  Counter-analysis
Explain the limitation / adverse consequence of the above policy & economic mechanism
with real Hong Kong economic phenomenon.

Paragraph 4  Evaluative Judgement (only for Evaluate questions)
Give a clear personal judgement, support your view with practical factors:
implementation cost, time lag, side effect on employment or local inflation.

配套高分衔接词库（L2 背诵入库）

• 转折：nevertheless / in contrast / on the contrary
• 因果：accordingly / consequently / as a result
• 评判：from a practical perspective / taking social cost into consideration

Evaluate 真题套用示范（模板配真题，告别只会背不会用）

真题题干：Evaluate the effectiveness of contractionary fiscal policy to curb local inflation in Hong Kong.

Para1 Definition: Contractionary fiscal policy refers to government raising tax rates or
cutting public spending to reduce aggregate demand in an economy.

Para2 Positive effect: Higher tax reduces household disposable income, consumption falls,
AD curve shifts left, general price level drops to ease inflation pressure.

Para3 Limitation: Cutting public spending will slow infrastructure construction and raise
short-term unemployment; tax adjustment has obvious time lag.

Para4 Judgement: This policy can relieve inflation in the long run, but the Hong Kong
government prefers using targeted subsidies rather than tight fiscal policy to avoid
harming local economic vitality.

宏观财政 & 货币政策标准答题句式（L1 背诵级）★★★

1. Contractionary Fiscal Policy

The government raises tax rate or cuts public expenditure to reduce aggregate demand, shifting AD curve leftwards, lowering general price level to ease inflation pressure, but it may increase unemployment in the short run.

2. Expansionary Monetary Policy

HKMA lowers the interbank interest rate, reducing the cost of borrowing for firms and households. Investment and consumption rise, aggregate demand increases to stimulate economic growth during recession.

月度时事背诵英文文段（Current Economic Issues 固定模块，每月 AI 更新替换）

范本（通用框架，AI 按月替换真实事件）

Topic: Hong Kong imported inflation under Linked Exchange Rate System

Hong Kong dollar is pegged to US dollar, so HKMA cannot adjust domestic interest rate independently to curb imported inflation. Surging global commodity prices raise the production cost of local retailers and catering industries, pushing up the overall consumer price index. The SAR government can use targeted subsidy policies to relieve citizens' living pressure, but fiscal subsidies will increase public financial burden in the long term.

答题使用提示：DRQ 问到香港通胀、汇率、楼市、进出口均可直接截取文段改写使用。

全年时事月度主题清单（AI 按此方向每月更新，不漫无目的生成）

月份	主题
1 月	香港楼市调控政策
3 月	港元联系汇率波动与输入通胀
5 月	香港旅游业复苏对本地 GDP 拉动
7 月	特区财政收支与公共补贴政策
9 月	国际贸易环境对本地进出口影响
11 月	绿色金融、ESG 产业在香港的发展

经济三类大题专属自查表（写完必逐项勾选）★★★

1）计算题自查：公式书写 ✅｜百分比计算正负值处理 ✅｜坐标轴标注 ✅｜最终英文判定语句 ✅

2）Short Answer 简答：定义前置 ✅｜因果逻辑连词 because/therefore ✅｜贴合题干材料 ✅

3）DRQ 大题：术语定义精准 ✅｜双面分析完整 ✅｜图表要素齐全 ✅｜无列表符号 ✅｜评判有理据 ✅｜EC 行文流畅 ✅

阅卷隐性扣分点（考生普遍不知道的规则）★★★

1. 画图曲线箭头画反方向，整道图表题直接 0 分，不会酌情给部分分数；
2. DRQ 全篇只用简单基础词汇，即便逻辑正确，EC 沟通分只会拿 1 分，拿不到满分 2 分；
3. 解释市场失灵题目，只罗列失灵类型、不结合香港本地实例，最高只能拿到 Band 4 水平。

微观 + 宏观高频真题陷阱清单 ★★★

1. 政府限价（Price ceiling / Price floor）：必须标注限价位置——ceiling 在均衡价格下方、floor 在均衡价格上方才生效，位置写反整题判错；
2. 货币创造：法定存款准备金率越高，货币乘数越小——很多学生逻辑写反；
3. 联系汇率制度：HKMA 只挂钩美元，港币汇率固定 7.8，央行无法自主加息降息——高频写作考点。

经济错题三级整改方案（配合错题档案使用）

错题级别	特征	整改动作
1 级（知识空白）	定义/原理不会	回看知识点原文定义 → 默写定义 → 3 道基础变式训练
2 级（审题/格式错误）	指令词看错、图表缺标注、用了列表符号	摘抄题干指令词，默写对应答题框架，重做同题型 2 题
3 级（论述逻辑单薄）	结构对但深度不够	仿写范文段落，积累对应论据，每周仿写一篇 DRQ

错题复盘分层规则：阶段1 按「微观/宏观单元」归档，补齐定义盲区；阶段2-4 按「计算题/短答题/DRQ 论述题」题型归档，总结同类答题结构漏洞。

DRQ 2025 香港通胀真题完整满分英文范文 ★★★

以下为 Evaluate the effectiveness of contractionary fiscal policy to curb local inflation in Hong Kong 的满分作答示范。

Para 1  Opening Definition
Inflation refers to a continuous and general rise in the general price level of goods
and services in an economy. Hong Kong adopts the linked exchange rate system pegged to
USD, so local monetary policy cannot be adjusted independently.

Para 2  Positive effect of contractionary fiscal policy
Higher tax reduces household disposable income, consumption falls, AD curve shifts
leftwards, general price level drops to ease inflation pressure.

Para 3  Limitation (Counter argument)
Long-term fiscal subsidy increases government budget deficit, and cannot curb imported
inflation caused by rising global commodity prices fundamentally. Tax adjustment also
has an obvious implementation time lag.

Para 4  Evaluative Judgement
Targeted subsidy can relieve short-term living burden, but contractionary fiscal policy
is more effective for long-term inflation control, though it will raise short-term
unemployment in related industries.

9 分图表大题三步满分模板 ★★★

1. Draw fully labelled diagram：包含坐标轴变量名 + 单位（Price: $ / Quantity: units），曲线正式名称（Demand Curve / Supply Curve / AD / AS），均衡点标注 Pe、Qe；
2. Explain shift mechanism with official economic definition：引用考评局原版定义 + because/therefore 因果链说明曲线移动方向；
3. Match Hong Kong local real economic example：结合香港本地实际经济现象（如联系汇率下的输入型通胀、旅游业复苏对 AD 的拉动）获得满分高分。

常见失分：只写结论、不画图 → 图表题直接丢失一半分数。

HKEAA 考生高频错误案例（来自考评局 Subject Report）★★★

错误类型	学生写法（❌）	标准写法（✅）
只写结论、无图表	"Demand will increase"	Draw D curve shift rightwards → label axis + Pe/Qe
Discuss 只写单边	"Inflation is bad because..."	Discuss = 正方 + 反方独立段落，缺一方封顶 2/6 分
DRQ 用 bullet points	• Point 1 • Point 2 • Point 3	段落式行文，禁用列表符号，否则 EC 2 分全扣
混淆 budget/trade deficit	"Trade deficit means government spending too much"	Budget deficit = gov expenditure > tax; Trade deficit = imports > exports
定义缺少关键词	"Inflation is price rising"	Inflation = a sustained increase in the general price level
曲线移动方向画反	Supply curve shifts right when cost rises	Cost↑ → Supply curve shifts left

AI Self-test Prompt（本科通用）

You are a certified HKDSE Economics examiner. Based on the unit I specify, generate: 3 definition questions + 2 diagram analysis questions + 1 DRQ mini essay (8 marks). All in standard HKEAA English.
After I answer in English, mark strictly: check definition wording accuracy, diagram labelling completeness, essay logic and EC marks. List every missing scoring point and tell me exactly which section of this page to revise.

Unit: [填写单元名，如 Elasticity]