2026 Edexcel IAS-Level Economics (XEC11) 模擬試題連答案詳解

Cross Elasticity of Demand (XED) is calculated as: \( XED = \frac{\% \Delta Q_Y}{\% \Delta P_X} = \frac{-15\%}{10\%} = -1.5 \). A negative XED value indicates that the two goods are complementary, as an increase in the price of one leads to a decrease in demand for the other.

1 mark for the correct option (B). (Method: Calculation yields -1.5, negative sign indicates complements).

A negative externality in production means that external costs are generated, so Social Marginal Cost (SMC) exceeds Private Marginal Cost (PMC) by the marginal external cost (MEC). Since the free market only accounts for private costs (where PMC = PMB), too much of the good is produced relative to the socially optimum level (where SMC = SMB), resulting in overproduction.

1 mark for the correct option (C). (SMC = PMC + External Cost, meaning SMC > PMC, leading to overproduction in a free market).

The opportunity cost of moving from J to K is the loss of capital goods divided by the gain in consumer goods. Opportunity Cost = \( \frac{\Delta \text{Capital Goods}}{\Delta \text{Consumer Goods}} = \frac{50 - 40}{110 - 80} = \frac{10}{30} = 0.33 \) capital goods per additional consumer good.

1 mark for the correct option (B). (Calculation: 10 / 30 = 0.33 capital goods).

In the circular flow of income, leakages (or withdrawals) are flows of money that leave the economy, which include Saving (S), Taxes (T), and Imports (M). Injections are Investment (I), Government spending (G), and Exports (X).

1 mark for the correct option (A). (S, T, and M are the three leaks).

When demand is perfectly price inelastic, consumers will purchase the exact same quantity regardless of price. The supply curve shifts upwards vertically by the tax amount, causing the equilibrium price paid by consumers to rise by the full amount of the tax. Consumer surplus decreases because they pay a higher price. Producer surplus is unchanged because the price received by producers net of tax remains exactly the same, and the quantity sold does not change.

1 mark for the correct option (C). (With perfectly inelastic demand, tax burden falls entirely on the consumer, reducing consumer surplus while leaving producer surplus unaffected).

A depreciation in the exchange rate of the domestic currency makes domestic exports cheaper for foreigners and imports more expensive for domestic residents. This increases the value of exports (X) and decreases the value of imports (M), leading to an increase in net exports (X-M), which is a key component of AD, thereby shifting the AD curve to the right.

1 mark for the correct option (B). (Depreciation improves net exports (X-M), shifting AD to the right).

1. Calculate percentage change in quantity demanded: \(\% \Delta Q_d = \frac{135,000 - 150,000}{150,000} \times 100 = -10\%\). 2. Calculate percentage change in price: \(\% \Delta P = \frac{92 - 80}{80} \times 100 = 15\%\). 3. Apply the PED formula: \(\text{PED} = \frac{\% \Delta Q_d}{\% \Delta P} = \frac{-10\%}{15\%} = -0.67\) (or 0.67 if using the absolute value).

1 mark for correct calculation of percentage change in quantity demanded (-10%). 1 mark for correct calculation of percentage change in price (15%). 1 mark for showing the correct PED formula. 1 mark for correct final answer of -0.67 (or 0.67).

1. Calculate percentage change in quantity demanded: \(\% \Delta Q_d = \frac{2,400 - 2,000}{2,000} \times 100 = 20\%\). 2. Calculate percentage change in income: \(\% \Delta Y = \frac{36,000 - 32,000}{32,000} \times 100 = 12.5\%\). 3. Calculate YED: \(\text{YED} = \frac{\% \Delta Q_d}{\% \Delta Y} = \frac{20\%}{12.5\%} = 1.6\). 4. Since the YED is positive and greater than 1, organic vegetables are a normal good (specifically a luxury or superior good).

1 mark for calculating the percentage change in quantity demanded (20%). 1 mark for calculating the percentage change in income (12.5%). 1 mark for correct calculation of YED (1.6). 1 mark for correctly identifying the good as a normal or luxury good.

To calculate real GDP, we use the formula: \(\text{Real GDP} = \frac{\text{Nominal GDP}}{\text{GDP Deflator}} \times 100\). Substituting the values: \(\text{Real GDP} = \frac{450}{120} \times 100 = 3.75 \times 100 = 375\) billion. Thus, the real GDP in 2022 was $375 billion.

1 mark for identifying the correct formula for real GDP. 2 marks for substituting the correct values into the formula (award 1 mark if only one value is substituted correctly). 1 mark for the final calculation of $375 billion (or 375).

The marginal propensity to withdraw (MPW) is the sum of leakages from the circular flow of income: \(\text{MPW} = \text{MPS} + \text{MPT} + \text{MPM}\). Substituting the values: \(\text{MPW} = 0.15 + 0.10 + 0.15 = 0.40\). The multiplier formula is: \(k = \frac{1}{\text{MPW}}\). Substituting the MPW value: \(k = \frac{1}{0.40} = 2.5\). Therefore, the value of the multiplier is 2.5.

1 mark for stating the multiplier formula, e.g., \(k = \frac{1}{\text{MPW}}\) or \(k = \frac{1}{1 - \text{MPC}}\). 1 mark for calculating the total marginal propensity to withdraw (MPW = 0.40) or marginal propensity to consume (MPC = 0.60). 1 mark for substituting the values into the multiplier formula. 1 mark for the final answer of 2.5.

1. Find the number of unemployed individuals: \(\text{Unemployed} = \text{Labour Force} - \text{Employed} = 30\text{ million} - 27.6\text{ million} = 2.4\text{ million}\). 2. Use the unemployment rate formula: \(\text{Unemployment Rate} = \frac{\text{Unemployed}}{\text{Labour Force}} \times 100\). 3. Calculate the rate: \(\text{Unemployment Rate} = \frac{2.4}{30} \times 100 = 8\%\). Therefore, the unemployment rate is 8%.

1 mark for calculating the number of unemployed people (2.4 million). 1 mark for stating the correct formula for the unemployment rate. 1 mark for substituting the correct values. 1 mark for the correct final answer of 8%.

Asymmetric information occurs when there is an imbalance of information between buyers and sellers in a market. One party (for example, a seller of a used car or a buyer of health insurance) possesses more accurate or detailed knowledge about the product or service than the other party. This imbalance of information prevents mutually beneficial transactions from occurring efficiently, potentially leading to adverse selection or moral hazard, which are forms of market failure.

Award 1 mark for identifying the core concept of unequal information:
- One party in a transaction/market has more or better information than the other party (1 mark).

Award 1 mark for development, consequence, or example:
- This leads to market failure / misallocation of resources (1 mark).
- This can lead to adverse selection or moral hazard (1 mark).
- An appropriate example, such as health insurance or second-hand cars (1 mark).

An explanation of the microeconomic effect of a price ceiling should focus on how it disrupts the free-market price mechanism:

1. **Theoretical Explanation (Knowledge):**
- A maximum price (price ceiling) is a government-imposed limit on the price of a product, set below the market equilibrium to protect consumers.
- Because the price is forced below the market-clearing level, it creates a disequilibrium where the quantity demanded (\(Q_D\)) exceeds the quantity supplied (\(Q_S\)), resulting in excess demand or a shortage.

2. **Application to Zephyrus:**
- The government set a maximum price of $2.50 per kg, which is below the free-market equilibrium of $4.00 per kg.
- At this lower price, quantity demanded is 500,000 tonnes while quantity supplied is only 250,000 tonnes.
- This leads to a persistent shortage of \(500,000 - 250,000 = 250,000\) tonnes per month, explaining the empty shelves reported by grain distributors.

**Knowledge & Understanding (2 marks):**
- **1 mark** for defining a maximum price / price ceiling (e.g., a government-set limit on price below the market equilibrium to assist consumers).
- **1 mark** for explaining that a price ceiling set below the equilibrium price leads to excess demand or a market shortage (as suppliers reduce output and consumers increase their quantity demanded).

**Application (2 marks):**
- **1 mark** for identifying the relevant price levels from the extract (e.g., maximum price of $2.50 per kg set below the market price of $4.00 per kg).
- **1 mark** for calculating or explicitly stating the resulting shortage (e.g., shortage of 250,000 tonnes, or showing the calculation: \(500,000\text{ tonnes} - 250,000\text{ tonnes} = 250,000\text{ tonnes}\)).

Diagrammatic Analysis:
- The horizontal axis is labelled Quantity (Q) and the vertical axis is labelled Price (P).
- The initial demand curve (D) and supply curve (\(S_1\)) intersect at the initial equilibrium point, establishing price \(P_1\) and quantity \(Q_1\).
- The introduction of a $0.50 specific indirect tax increases the cost of production for beverage manufacturers. This shifts the supply curve vertically upwards to \(S_2\), where the vertical distance between \(S_1\) and \(S_2\) equals the tax of $0.50.
- At the original price \(P_1\), there is now excess demand, which forces the market price up to the new equilibrium price \(P_2\).
- The increase in price leads to a contraction along the demand curve, resulting in a lower equilibrium quantity of \(Q_2\).
- Consequently, the policy successfully reduces the production and consumption of plastic-packaged beverages, helping to internalise the negative externality.

Diagram (3 marks):
- 1 mark for drawing and labelling the initial equilibrium with \(P_1\) and \(Q_1\) (axes and curves correctly labelled).
- 1 mark for showing a parallel upward shift of the supply curve from \(S_1\) to \(S_2\).
- 1 mark for showing the new equilibrium price \(P_2\) and quantity \(Q_2\).

Written Analysis (3 marks):
- 1 mark for identifying that the indirect tax increases manufacturers' costs of production (referencing the $0.50 tax from Extract A).
- 1 mark for explaining that this reduction in supply causes the price to rise, leading to a contraction in quantity demanded.
- 1 mark for explaining that the new equilibrium leads to a lower quantity traded (\(Q_2\)), which reduces the level of plastic waste/external costs.

### Solution

**Factor 1: Price Elasticity of Demand (PED) and the availability of close substitutes**
- **Analysis**: An indirect tax increases the cost of production, shifting the supply curve to the left and raising the retail price. If the demand for sugary drinks is relatively price elastic (\(PED > 1\)), a price increase leads to a more than proportionate decrease in quantity demanded, making the tax highly effective. Extract A notes a \(30\%\) reduction in purchasing, indicating a strong responsive demand.
- **Evaluation**: However, the overall effectiveness on health depends on *what* consumers substitute to. Extract A mentions that consumers switched to 'cheaper untaxed store-brand alternatives or fruit juices'. If consumers substitute one high-sugar beverage for another untaxed sugary option, the overall consumption of sugar may not decline, reducing the policy's effectiveness.

**Factor 2: Supply-side response / Product Reformulation by manufacturers**
- **Analysis**: The structure of the tax (only taxing sugar above 4g per 100ml) incentivises producers to reformulate their drinks to avoid the levy. Extract A states that 'manufacturers reformulated their recipes'. This reduces the sugar content per drink sold, which successfully reduces aggregate sugar consumption without requiring consumers to change their buying habits.
- **Evaluation**: However, reformulation may be limited by consumer preferences; if reformulated drinks taste worse, sales might crash, or firms may choose to pay the tax and pass the cost to consumers instead. Additionally, the long-run effectiveness depends on whether the tax is set high enough to outweigh the research and development costs of reformulation.

### Marking Scheme (8 Marks Total)

**Knowledge, Application, and Analysis (6 Marks - Level 1 to 3)**
- **1–2 marks (Level 1)**: Identifies one or two factors (e.g., PED, substitutes, reformulation) with basic definitions of indirect tax or PED. No explicit reference to the extract.
- **3–4 marks (Level 2)**: Explains one or two factors with some application to Extract A (e.g., referencing the \(30\%\) drop or reformulation). Basic chain of reasoning showing how these factors affect consumption.
- **5–6 marks (Level 3)**: Detailed economic analysis of two distinct factors, fully integrated with Extract A. Clear chain of reasoning linking the tax, price changes, consumer/producer responses, and the final impact on sugar consumption.

**Evaluation (2 Marks)**
- **1 mark**: Offers a basic evaluative point (e.g., noting that substituting to other sugary drinks reduces effectiveness, or that short-run vs long-run effects differ).
- **2 marks**: Provides balanced evaluation of both factors, perhaps discussing the significance of the tax rate or the role of consumer tastes in determining the ultimate success of the tax.

### KAA (Knowledge, Application and Analysis) - 8 Marks

**Key terms and concepts:**
- **Negative externality of production:** Negative third-party effects occurring during the manufacturing process (e.g., pollution, environmental degradation from plastics).
- **Indirect tax:** A tax levied on goods and services, which increases the cost of production for firms.

**Diagram details:**
- Axes: Price (P) on the vertical axis, Quantity (Q) on the horizontal axis.
- Curves: Downward-sloping Marginal Private Benefit (MPB) / Marginal Social Benefit (MSB) curve. Upward-sloping Marginal Private Cost (MPC) and Marginal Social Cost (MSC) curves, where MSC lies above MPC.
- Market equilibrium: Occurs where \(MPC = MPB\) (Price \(P_1\), Quantity \(Q_1\)).
- Social optimum: Occurs where \(MSC = MSB\) (Price \(P_{so}\), Quantity \(Q_{so}\)).
- Welfare loss / deadweight loss: Triangle pointing to the social optimum (area between MSC and MSB from \(Q_{so}\) to \(Q_1\)).
- Impact of tax: Shifts the MPC curve vertically upwards by the amount of the tax to \(MPC + Tax\). If set correctly, this matches MSC, reducing output to \(Q_{so}\) and increasing price to \(P_{so}\), thereby eliminating the deadweight loss.

**Analysis points:**
- The tax internalises the negative externality by forcing manufacturers to pay for the environmental damage they cause.
- Higher production costs discourage the production of single-use plastics, incentivising firms to invest in biodegradable or recyclable alternatives.
- Tax revenue generated can be ring-fenced by the government to subsidise green alternatives or fund cleanup operations.

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### Evaluation (Ev) - 6 Marks

**Evaluative points:**
- **Price Elasticity of Demand (PED):** If the demand for goods using single-use plastics is highly inelastic (e.g., essential groceries), consumers will bear most of the tax burden (regressive effect) and the reduction in quantity traded will be minimal, meaning the environmental benefit is limited.
- **Measurement difficulty:** It is extremely difficult for governments to place an accurate monetary value on environmental degradation (MEC). If the tax is set too high or too low, it can lead to government failure.
- **Unintended consequences:** Firms might bypass the tax by smuggling plastic materials, or shift to alternative packaging materials (like paper) which could have their own environmental footprints (deforestation, high water usage).
- **Regressive impact:** Lower-income households spend a larger proportion of their income on basic groceries, which are often wrapped in plastic packaging. A rise in prices could exacerbate poverty and inequality.

### Marking Scheme

#### KAA (Knowledge, Application and Analysis) [8 Marks]
- **Level 3 (6-8 Marks):** Fully accurate and well-labelled negative externalities diagram showing the original market failure, the tax shifting MPC, the new equilibrium, and the reduction in deadweight loss. Strong analytical links showing how the tax internalises the externality, with clear contextual reference to single-use plastics.
- **Level 2 (3-5 Marks):** Diagram is mostly correct but may have minor labelling errors or missing elements (e.g., welfare loss triangle not clearly shown). Some analytical explanation of the tax, but links to the context are weak or superficial.
- **Level 1 (1-2 Marks):** Basic definition of terms or a poorly drawn diagram. Lacks logical analytical steps.

#### Evaluation (Ev) [6 Marks]
- **Level 3 (5-6 Marks):** At least two strong evaluative points developed in depth (e.g., PED arguments, measurement issues, regressive impacts). Offers a balanced conclusion on overall effectiveness.
- **Level 2 (3-4 Marks):** Some evaluative points are identified and explained, but lack depth or context.
- **Level 1 (1-2 Marks):** Generic evaluative comments with little to no economic reasoning.

Indicative content: Introduction: Define a maximum price as a legally established limit above which sellers cannot charge, set below the market equilibrium to protect consumers. Explain that rent control is a classic microeconomic example of this. Diagrammatic analysis: The response should describe or imply a supply and demand diagram for rental housing. The vertical axis shows rent (Price) and the horizontal axis shows quantity of rental units (Quantity). Show a downward-sloping demand curve (D) and an upward-sloping supply curve (S) intersecting at equilibrium \( (P_e, Q_e) \). Draw a horizontal line representing the maximum price \( (P_{max}) \) below \( P_e \). Show that at \( P_{max} \), the quantity demanded \( (Q_d) \) exceeds the quantity supplied \( (Q_s) \), creating a market shortage (excess demand of \( Q_d - Q_s \)). Analysis of positive impacts (KAA): 1. Affordability: Existing low-income tenants benefit from cheaper rents, increasing their consumer surplus and real disposable income, which can reduce relative poverty and inequality. 2. Stability: It prevents landlords from exploiting tenants with sudden, excessive rent increases, providing housing stability for families. Analysis of negative impacts (KAA): 1. Housing Shortage: Because rents are artificially low, some landlords may withdraw properties from the market or convert them to other uses, while demand increases, creating a shortage of housing. 2. Quality Deterioration: Landlords have less incentive and fewer financial resources to maintain and repair properties, leading to a decline in the quality of the rental housing stock. 3. Shadow/Black Markets: Landlords may demand under-the-table payments (such as 'key money' or inflated fees for furniture) to bypass the rent ceiling, rendering the policy ineffective. 4. Inefficient Allocation: Long waiting lists and queuing replace price as the rationing mechanism. Landlords may discriminate when choosing tenants since they have an excess of applicants. Evaluation points: 1. Price Elasticity of Supply (PES): In the short run, the supply of housing is highly inelastic, meaning the shortage created is relatively small. However, in the long run, supply is much more elastic as developers stop building new rental units and landlords exit the market, making the shortage much worse over time. 2. Enforcement and Administration Costs: The policy requires continuous monitoring and enforcement by the government to prevent illegal subletting or black-market transactions, representing a high opportunity cost of public funds. 3. Alternative Policies: Instead of price ceilings, governments could use supply-side policies (e.g., building municipal social housing, offering tax incentives for developers) or demand-side policies (e.g., housing vouchers for low-income families) which do not distort the market mechanism to the same extent. 4. Judgement: While rent controls provide short-term relief to a specific group of existing tenants, they often lead to severe long-term market distortions and reduce the overall welfare of prospective renters.

Marking scheme breakdown (Total: 20 marks): Knowledge, Application, and Analysis (KAA) = 12 marks. Level 4 (10-12 marks): Strong, precise economic analysis of a range of microeconomic effects (e.g., shortage, quality decline, consumer/producer surplus changes) with an accurate, fully labeled diagram showing maximum price below equilibrium and the resulting disequilibrium. Level 3 (7-9 marks): Clear analysis of effects with some development. A diagram is included but may have minor labeling errors. Level 2 (4-6 marks): Basic application and analysis of maximum price, limited explanation of effects, diagram may be missing or incorrect. Level 1 (1-3 marks): Identification of basic points (e.g., defining maximum price) with no real analysis. Evaluation = 8 marks. Level 3 (7-8 marks): Deep, balanced evaluation discussing short-run vs long-run impacts (e.g., elasticity differences), magnitude of effects, and comparison with alternative policies. Concludes with a reasoned judgment. Level 2 (4-6 marks): Explanation of some evaluative points (e.g., quality reduction or black markets) but lacks depth or a balanced conclusion. Level 1 (1-3 marks): Identifies one or two basic evaluative points without explanation.