2024 IB DP Economics 模擬試題連答案詳解

To prevent its currency from depreciating, a central bank can use direct and indirect intervention. First, through direct intervention, the central bank sells its reserves of foreign currencies (such as US dollars) and buys its own currency in the foreign exchange market. This increases the demand for the domestic currency, shifting the demand curve to the right, which supports or raises its price (the exchange rate). Second, through indirect intervention, the central bank can raise domestic interest rates. Higher interest rates offer foreign investors a higher rate of return on savings and financial assets in that country. This leads to an inflow of financial capital (often called 'hot money'), increasing the demand for the domestic currency as investors convert foreign currency to buy domestic assets, thereby shifting the demand curve to the right. A diagram showing the foreign exchange market of the domestic currency is essential. The vertical axis represents the price of the domestic currency in terms of a foreign currency, and the horizontal axis represents the quantity of the domestic currency. When the central bank intervenes, the demand curve shifts from \(D_1\) to \(D_2\), preventing the exchange rate from falling below a target level. Two key reasons why a country might want to prevent depreciation are: 1. Preventing imported inflation: A depreciating currency makes imported goods, raw materials, and energy more expensive in domestic terms. For a country reliant on imports, this can lead to cost-push inflation, reducing the purchasing power of consumers and raising production costs for firms. 2. Reducing the burden of foreign debt: If a government or domestic corporations have borrowed in foreign currencies, a depreciation of the domestic currency increases the value of the debt and the interest payments in terms of the domestic currency, which can trigger a fiscal crisis or default. A real-world example of this occurred in Turkey, where the central bank repeatedly raised interest rates to support the Turkish Lira and curb inflation, or Switzerland's central bank historical interventions.

Assessment Criteria for Part (a) (10 Marks): Level 1 (1-3 Marks): Demonstrates limited understanding of exchange rate intervention. Terminology is vague or inaccurate. Diagram is missing or incorrect. No real-world example is mentioned. Level 2 (4-6 Marks): Demonstrates some understanding of how a central bank intervenes, explaining either foreign exchange reserves or interest rates. Explains at least one reason why depreciation is avoided. A foreign exchange diagram is present but may have minor labeling errors. Level 3 (7-8 Marks): Clear explanation of both intervention methods (selling reserves and raising interest rates). Explains two reasons to avoid depreciation (imported inflation and debt burden). Includes a correctly drawn and fully labeled foreign exchange diagram. Refers to a relevant real-world example. Level 4 (9-10 Marks): Highly detailed and accurate response. Demonstrates a thorough understanding of foreign exchange market mechanisms, using terms like hot money, foreign reserves, and cost-push inflation. The diagram is fully integrated into the explanation, and a well-developed real-world example is used effectively to support the theory.

### Introduction
- **Definitions**: Define key terms including *currency depreciation* (a decrease in the value of a currency in a floating or managed exchange rate system), *economic growth* (an increase in real GDP over time), and *unemployment* (the state of being actively looking for work but unable to find it).
- **Context**: State that a government or central bank can deliberately influence its currency to depreciate (e.g., through managed depreciation, lowering interest rates, or selling its currency in the forex market) to improve international competitiveness.

### Diagrams to Include
1. **Foreign Exchange Market Diagram**: Showing an increase in the supply of the domestic currency (or decrease in demand) causing the exchange rate to fall from \(ER_1\) to \(ER_2\).
2. **AD/AS Diagram**: Showing the aggregate demand curve shifting to the right from \(AD_1\) to \(AD_2\), leading to an increase in real output from \(Y_1\) to \(Y_2\) and an increase in the price level from \(PL_1\) to \(PL_2\).

### Synthesis and Analysis
- **Mechanisms of Growth and Employment Generation**:
- A weaker currency makes exports cheaper for foreign buyers and imports more expensive for domestic consumers.
- This changes the relative prices, leading to an increase in export volume (X) and a decrease in import volume (M).
- Since net exports \((X-M)\) is a component of Aggregate Demand \(AD = C + I + G + (X-M)\), the AD curve shifts to the right.
- The increase in real GDP \((Y_1 \to Y_2)\) increases the demand for labor (as labor is a derived demand), thereby reducing cyclical unemployment.
- **The Marshall-Lerner Condition & J-Curve**:
- Explain that for depreciation to improve the net export balance, the sum of the price elasticities of demand for exports and imports must be greater than 1: \(PED_x + PED_m > 1\).
- In the short run, this may not hold, leading to a temporary worsening of the current account (the J-curve effect).

### Evaluation and Discussion (Counterarguments & Limitations)
- **Inflationary Risks**:
- **Cost-push inflation**: Imported raw materials, components, and energy become more expensive, shifting the Short-Run Aggregate Supply (SRAS) curve to the left, which can cause stagflation (lower growth, higher unemployment, higher inflation).
- **Demand-pull inflation**: If the economy is already operating close to full capacity, the rightward shift in AD will primarily lead to inflation rather than real output growth.
- **Retaliation (Currency Wars)**:
- Deliberate depreciation (competitive devaluation) can provoke trading partners to impose trade barriers (tariffs) or depreciate their own currencies, neutralizing any competitive advantage.
- **Ineffectiveness for Structural Problems**:
- If unemployment is structural rather than cyclical, AD stimulation will not resolve the skills mismatch in the labor market.
- **Comparison with Alternative Policies**:
- **Supply-side policies**: Investment in education, infrastructure, and R&D shifts the Long-Run Aggregate Supply (LRAS) curve to the right, creating non-inflationary, sustainable growth.
- **Fiscal/Monetary Stimulus**: Direct domestic demand management might be more controllable and less disruptive to global trade relations.

### Real-World Examples
- **Japan (Abenomics)**: Deliberate depreciation of the Yen starting in 2012 to escape deflation and boost export-led growth, with mixed success due to structural demographic issues.
- **China**: Historically accused of keeping the Yuan undervalued to support its massive export-oriented manufacturing sector and maintain high employment levels.

### Markbands (15 Marks total)

- **Level 1 (1–3 marks)**:
- Lacks understanding of the term currency depreciation or its connection to macroeconomic goals.
- No diagrams or heavily inaccurate diagrams.
- Entirely descriptive response.

- **Level 2 (4–6 marks)**:
- Simple definition of currency depreciation and macroeconomic goals.
- Diagrams are present but have labeling errors or are not integrated into the text.
- Explains how depreciation increases exports and AD, but lacks depth and does not address limitations.

- **Level 3 (7–9 marks)**:
- Well-defined terms.
- Correctly drawn and labeled diagrams showing depreciation (Forex market) and the shift in AD.
- Explains the transmission mechanism from depreciation to economic growth and reduced unemployment.
- Lacks balanced evaluation; focuses mostly on the positive effects or has a very superficial counter-argument.

- **Level 4 (10–12 marks)**:
- Detailed analysis of both the advantages and disadvantages of deliberate currency depreciation.
- Includes economic concepts such as the Marshall-Lerner condition, J-curve, and cost-push inflation.
- Includes a real-world example (e.g., Japan, China, or eurozone dynamics).
- Evaluation is present but may lack depth, or fails to compare it effectively with alternative policies.

- **Level 5 (13–15 marks)**:
- Excellent, well-structured essay demonstrating deep economic understanding.
- Seamless integration of diagrams (Forex and AD/AS) with precise explanations.
- Strong, balanced evaluation addressing short-run vs. long-run impacts, elasticities, inflationary consequences, and retaliation risks.
- Provides a clear judgment/conclusion on whether it is the "most effective" policy relative to alternatives like supply-side reforms.
- Relevant and well-integrated real-world examples.

Common pool resources are characterized by two main attributes: 1. Non-excludability: Users cannot easily be excluded from accessing or using the resource. 2. Rivalry: Consumption by one individual reduces the amount available for others, leading to potential degradation or overuse (often referred to as the 'tragedy of the commons'). Examples include fish stocks in international waters or public forests.

Award [1] for stating that the resources are non-excludable (or difficult to exclude people from). Award [1] for stating that the resources are rivalrous (or one person's consumption reduces availability for others). Max [1] if only one characteristic is correctly identified or if an example is given without defining both key characteristics.

In a managed exchange rate system, the currency is allowed to float freely in response to market forces on a day-to-day basis. However, the central bank or government will step in and buy or sell its own currency using foreign reserves to stabilize the currency, prevent sudden depreciation/appreciation, or influence economic performance.

Award [1] for explaining that the exchange rate is primarily determined by market forces (demand and supply). Award [1] for explaining that the central bank or government intervenes in the foreign exchange market to influence or stabilize the rate.

A quota is a trade barrier that restricts the volume of imports. By limiting the supply of foreign goods, it raises the domestic price of the imported good, thereby protecting domestic producers from foreign competition.

Award [1] for stating it is a physical limit or restriction on imports. Award [1] for specifying that it refers to the quantity or value of goods/services allowed into the country over a given time period.

Absolute poverty is measured against a fixed standard, such as the World Bank's international poverty line (e.g., $2.15 a day). It represents an extreme state of deprivation where biological survival is threatened due to a lack of essential resources, unlike relative poverty which is measured against the average income in a society.

Award [1] for identifying that it is a lack of income to meet basic/essential human needs (such as food, water, or shelter). Award [1] for mentioning that it is defined relative to an absolute/fixed standard or poverty line (or distinguishing it from relative poverty which changes with societal average income).

Percentage change in Price = \(\frac{5.50 - 5.00}{5.00} \times 100 = 10\%\). Percentage change in Quantity Demanded = \(\frac{850 - 1000}{1000} \times 100 = -15\%\). PED = \(\frac{-15\%}{10\%} = -1.5\) (or 1.5 in absolute terms).

Award 1 mark for correct working showing percentage changes or correct substitution into the PED formula. Award 0.7 marks for the correct final answer of -1.5 (accept 1.5).

The current account balance is calculated as: Current Account Balance = Balance of trade in goods + Balance of trade in services + Primary income balance + Secondary income balance = \(-45 + 15 + (-12) + (-8) = -50\) billion USD.

Award 1 mark for showing correct working (adding the components of the current account and correctly excluding the capital account). Award 0.7 marks for the correct final answer of -50 (or -50 billion USD).

Percentage appreciation of the Euro = \(\frac{1.35 - 1.25}{1.25} \times 100 = \frac{0.10}{1.25} \times 100 = 8.0\%\).

Award 1 mark for correct working of the percentage change. Award 0.7 marks for the correct final answer of 8 (or 8%).

The Marginal Social Cost (MSC) is MSC = MPC + MEC = \(60 + Q + 30 = 90 + Q\). Since there are no consumption externalities, Marginal Social Benefit (MSB) = MPB = 300 - 2Q. The social optimum occurs where MSB = MSC: \(300 - 2Q = 90 + Q\) implies \(3Q = 210\), and thus \(Q = 70\) tonnes.

Award 1 mark for setting up the correct equation MSB = MSC (or determining MSC = 90 + Q). Award 0.7 marks for the correct final answer of 70.

Real GDP = \(\frac{\text{Nominal GDP}}{\text{GDP Deflator}} \times 100 = \frac{525}{105} \times 100 = 5 \times 100 = 500\) billion USD.

Award 1 mark for correct substitution of values into the Real GDP formula. Award 0.7 marks for the correct final answer of 500.

Quintile ratio = \(\frac{\text{Income share of richest 20\%}}{\text{Income share of poorest 20\%}} = \frac{48\%}{8\%} = 6\).

Award 1 mark for correct working or formula setup. Award 0.7 marks for the correct final answer of 6.

To maximize profit, the monopolist produces where MR = MC: \(100 - 8Q = 10 + 2Q\). Rearranging gives \(90 = 10Q\), which yields \(Q = 9\).

Award 1 mark for setting MR = MC. Award 0.7 marks for the correct final answer of 9.

At the price ceiling of \(P = 12\): \(Q_d = 120 - 4(12) = 72\) thousand units. \(Q_s = -20 + 6(12) = 52\) thousand units. Shortage = \(Q_d - Q_s = 72 - 52 = 20\) thousand units.

Award 1 mark for correct calculation of both quantity demanded (72) and quantity supplied (52) at the price ceiling. Award 0.7 marks for the correct final answer of 20.

1. Determine the initial value of 1 NVD in terms of USD: 1 / 4.00 = 0.25 USD. 2. Determine the new value of 1 NVD in terms of USD: 1 / 5.00 = 0.20 USD. 3. Calculate the percentage change in the value of the NVD: ((0.20 - 0.25) / 0.25) * 100 = -20%. This negative percentage change indicates a depreciation of 20% against the USD.

[1 mark] for correctly setting up the percentage change calculation using the reciprocal values, e.g., ((0.20 - 0.25) / 0.25) * 100. [0.7 mark] for the correct final answer of 'depreciation of 20%' or '-20%'. If the student only states '20%' without indicating it is a depreciation or negative, deduct 0.7 marks.

To explain this using a negative externality of production diagram: 1. Identify that coal-fired electricity generation creates external costs, meaning that the Marginal Social Cost (MSC) is greater than the Marginal Private Cost (MPC). 2. The free-market equilibrium occurs where Marginal Private Benefit (MPB) equals MPC, resulting in price Pm and quantity Qm. 3. The socially optimum level of output is where MSC equals MSB, resulting in price Popt and quantity Qopt. 4. A carbon tax equal to the external cost shifts the MPC curve upwards to coincide with the MSC curve (MPC + tax = MSC). This internalizes the externality, raising the price paid by consumers to Popt and reducing the quantity demanded and produced to Qopt, thereby eliminating the deadweight welfare loss.

For a complete explanation: [1 mark] for explaining that a carbon tax increases the private cost of production, shifting the MPC curve upwards/leftwards towards the MSC curve. [1 mark] for explaining that the tax internalizes the external cost, raising the market price from Pm to Popt. [1 mark] for explaining that the quantity produced and consumed falls from the over-allocated free-market level (Qm) to the socially optimum level (Qopt). [1 mark] for explaining that this reallocation of resources eliminates the deadweight welfare loss associated with overproduction.

To explain this using an exchange rate diagram: 1. An increase in the benchmark interest rate makes financial assets in Country X more attractive to foreign investors seeking higher returns. 2. To purchase these assets, foreign investors must first acquire the Rex. This increases the demand for the Rex, shifting the demand curve to the right from D1 to D2. 3. At the same time, domestic investors are less likely to invest abroad, reducing the supply of the Rex in the foreign exchange market, which shifts the supply curve to the left from S1 to S2. 4. Both the increase in demand and the decrease in supply put upward pressure on the price of the Rex, causing its exchange rate to appreciate from ER1 to ER2.

For a complete explanation: [1 mark] for explaining that higher interest rates attract foreign financial investment (hot money inflows) seeking higher returns. [1 mark] for explaining that this increases the demand for the currency, shifting the demand curve to the right. [1 mark] for explaining that domestic investors retain funds domestically, decreasing the supply of the currency (shifting the supply curve to the left). [1 mark] for explaining that the combined effect of these shifts leads to an increase in the exchange rate (appreciation) from ER1 to ER2.

To explain this using a tariff diagram: 1. The imposition of a tariff of size t raises the domestic price of imported steel from the world price Pw to Pw + t. 2. Domestic consumers now face a higher price, which reduces their total consumption of steel from Q4 to Q3. Consequently, consumer surplus decreases. 3. Domestic steel producers are protected by the tariff and can now sell their output at the higher price of Pw + t. This incentivizes them to expand domestic production from Q1 to Q2. 4. As a result, domestic producer surplus increases, but there is an overall welfare loss (deadweight loss) due to production inefficiency and consumption inefficiency.

For a complete explanation: [1 mark] for explaining that the tariff shifts the world supply curve upward, raising the domestic price of steel from Pw to Pw + t. [1 mark] for explaining that the higher price causes domestic consumers to reduce consumption (from Q4 to Q3), leading to a reduction in consumer surplus. [1 mark] for explaining that domestic producers expand production (from Q1 to Q2) due to the higher price, which increases domestic producer surplus. [1 mark] for explaining that this protection leads to welfare losses (deadweight loss) due to production and consumption inefficiencies.

### Policy Recommendation Analysis

**1. Identification of the Market Failure**
- The production of electricity using coal creates negative externalities of production (air pollution, PM2.5 emissions, health issues).
- This causes a divergence between marginal private cost (MPC) and marginal social cost (MSC): \(\text{MSC} = \text{MPC} + \text{MEC}\).
- Given the data, \(\text{MPC} = \$0.12\) and \(\text{MEC} = \$0.08\), making the true \(\text{MSC} = \$0.20\) per kWh. Because the market ignores the MEC, coal-fired electricity is overprovided and underpriced, leading to a welfare loss (deadweight loss).

**2. Evaluation of Option 1: Pigouvian Tax of \(\$0.08\) per kWh**
- **Mechanism**: A tax equal to the MEC (\(\$0.08\) per kWh) shifts the MPC curve upwards until it coincides with the MSC curve (\(\text{MPC}_{\text{tax}} = \text{MSC}\)). This internalizes the externality, forcing producers to pay the full social cost.
- **Outcome**: The market price of coal electricity rises to reflect its true social cost, reducing the quantity demanded and produced to the socially optimum level (where \(\text{MSB} = \text{MSC}\)), thus eliminating the deadweight loss.
- **Strengths**: It adheres to the 'polluter-pays' principle, provides incentives for coal plants to adopt cleaner technology, and generates tax revenue for the government.
- **Weaknesses**: The tax is regressive as energy costs rise, disproportionately hurting low-income households. It may also face political resistance from industrial lobbies.

**3. Evaluation of Option 2: Subsidy of \(\$0.06\) per kWh for Renewables**
- **Mechanism**: A subsidy to renewable energy shifts the MPC of clean energy downwards, lowering its market price and encouraging consumers to substitute away from coal.
- **Strengths**: Increases the market share of clean energy without directly raising prices for consumers, making it politically popular.
- **Weaknesses**: It does not directly penalize coal emissions; coal-fired plants may continue operating if baseload demand is high. It carries a heavy opportunity cost for the government budget (taxpayer-funded) and does not achieve perfect allocative efficiency because the subsidy rate (\(\$0.06\)) does not equal the MEC of coal (\(\$0.08\)).

**4. Synthesis and Recommendation**
- Option 1 is the superior policy because it directly targets the source of the market failure (coal production) and internalizes the exact value of the externality (\(\$0.08\)), correcting the market price signal.
- Furthermore, the government can use the tax revenues generated from Option 1 to fund renewable infrastructure or provide targeted rebates to low-income households to offset the regressive nature of the tax, achieving both efficiency and equity.

**[1–2 marks]**: Very limited response. Identifies some economic terms but lacks clear focus on the policy recommendation or the data provided.

**[3–4 marks]**: Explains either the tax or the subsidy using some data from the text (e.g., MEC of \(\$0.08\) or PM2.5 levels). Lacks deep evaluation of both options.

**[5–6 marks]**: Evaluates both options using economic theory (externalities, MPC/MSC) and the provided data. Shows a clear understanding of the difference between internalizing the externality (Option 1) and promoting substitutes (Option 2).

**[7–8 marks]**: Provides a balanced comparison of both policies. Evaluates the efficiency of the \(\$0.08\) tax versus the \(\$0.06\) subsidy, noting that the tax directly targets the MEC. Identifies trade-offs such as the opportunity cost of subsidies and the regressive nature of taxes.

**[9–10 marks]**: Direct, well-justified recommendation of one policy (or a synthesized combination, e.g., taxing coal and using revenues to fund transition). Fully integrates the provided data (e.g., PM2.5 levels, MEC of \(\$0.08\) per kWh, private cost of \(\$0.12\) per kWh) into a cohesive, highly structured economic argument.

### Policy Recommendation Analysis

**1. Understanding the Policy Context**
- Country Beta has a massive current account deficit (\(8\%\) of GDP) and a fixed exchange rate system that is under speculative pressure, evidenced by a \(40\%\) drop in foreign exchange reserves.
- To defend the peg, the government must reduce the supply of B$ in the foreign exchange market by correcting the trade deficit (reducing imports, \(M\), or boosting exports, \(X\)).

**2. Evaluation of Option A: Contractionary Fiscal Policy (5% Income Tax Increase)**
- **Mechanism**: Raising income taxes reduces household disposable income, which dampens consumer spending (\(C\)). Since a portion of consumer spending goes toward imports, \(M\) will decrease directly, improving the trade balance.
- **Impact on the Exchange Rate Peg**: By lowering aggregate demand (AD), contractionary fiscal policy reduces domestic inflationary pressures. Lower relative inflation makes domestic exports more price-competitive and imports relatively less attractive, further improving the current account and reducing the need for the central bank to sell foreign reserves to support the B$.
- **Macroeconomic Identity**: From the identity \(\text{Current Account} = (S - I) + (T - G)\), raising taxes (\(T\)) improves the government's budget position, which directly helps close the national savings-investment gap.
- **Drawbacks**: It will cause a contraction in real GDP, likely leading to a recessionary gap and higher unemployment, which is politically unpopular.

**3. Evaluation of Option B: 15% Uniform Tariff on Imported Consumer Goods**
- **Mechanism**: A tariff increases the domestic price of imported consumer goods, prompting consumers to switch to domestic substitutes.
- **Impact on the Current Account**: While this might reduce \(M\) in the short run, it does not address the underlying macroeconomic cause of the deficit (expenditure exceeding national income).
- **Drawbacks**:
- **Retaliation**: Trading partners are highly likely to retaliate with their own tariffs, which would cause Beta's exports (\(X\)) to fall, potentially leaving the current account deficit unchanged or worse.
- **Inflationary Pressure**: Tariffs raise the domestic price level, which could worsen inflation, harming the long-term competitiveness of Beta's exports and putting more downward pressure on the fixed peg.
- **WTO Rules**: Imposing a blanket tariff violates international trade rules and could lead to trade disputes.

**4. Synthesis and Recommendation**
- Option A (Contractionary Fiscal Policy) is the recommended policy. While it causes short-term domestic economic pain (lower growth and employment), it is the only sustainable way to correct a structural current account deficit of \(8\%\) under a fixed exchange rate regime.
- Option B (Tariffs) is a protectionist measure that will likely cause retaliation, fail to correct the structural savings-investment gap, and spark inflation, which would hasten the collapse of the currency peg.

**[1–2 marks]**: Shows limited understanding of the balance of payments or the policies. Simply states a choice without economic reasoning.

**[3–4 marks]**: Identifies how either fiscal policy or tariffs affect imports, referencing some data (e.g., the \(8\%\) deficit or the fixed peg). Explanations are mostly descriptive rather than analytical.

**[5–6 marks]**: Explains both options. Shows how contractionary fiscal policy reduces imports via disposable income, and how tariffs raise import prices. Begins to link these to the fixed exchange rate and reserve loss (\(40\%\) decline).

**[7–8 marks]**: Provides a structured comparison of both policies. Evaluates Option A's impact on domestic inflation and competitiveness, and Option B's risk of retaliation and trade inefficiency. Directly addresses the implications of the fixed exchange rate system.

**[9–10 marks]**: Delivers a highly effective, well-reasoned policy recommendation. Integrates the macroeconomic identity (savings-investment gap) or the threat of reserve depletion to justify why fiscal policy is structurally superior to protectionism. Fully utilizes all key data points (\(8\%\) deficit, peg, \(40\%\) reserves decline) to support the conclusion.