2025 Edexcel IAL Economics (YEC11) 模擬試題連答案詳解

The market equilibrium quantity is determined where marginal private benefit (MPB) equals marginal private cost (MPC). From the table, MPB = MPC = £30 at a quantity of 3,000 vaccinations. The socially optimum quantity is determined where marginal social benefit (MSB) equals marginal social cost (MSC). From the table, MSB = MSC = £40 at a quantity of 4,000 vaccinations. Therefore, the market equilibrium is 3,000 and the social optimum is 4,000.

1 mark for the correct combination of market equilibrium (3,000) and socially optimum quantity (4,000). Reject all other options.

The economic incidence of a tax depends on the relative elasticities of demand and supply. Since the price elasticity of demand is highly inelastic (0.2) and the price elasticity of supply is highly elastic (1.5), consumers are much less responsive to price changes than producers. Consequently, consumers will bear the larger share of the tax burden, meaning the consumer tax burden is greater than the producer tax burden.

1 mark for identifying that the consumer tax burden is greater than the producer tax burden because demand is relatively more inelastic than supply. Reject other choices.

An increase in government subsidies to manufacturers reduces their production costs, shifting the supply curve of electric vehicles to the right, which lowers the equilibrium price and increases the equilibrium quantity. An increase in the price of electricity (a complementary good) reduces the demand for electric vehicles, shifting the demand curve to the left, which lowers both the equilibrium price and equilibrium quantity. Combined, both shifts cause the equilibrium price to decrease. However, the net effect on equilibrium quantity is uncertain as it depends on the magnitude of the shifts.

1 mark for identifying that the equilibrium price decreases and the equilibrium quantity is uncertain. Reject other combinations.

The cross elasticity of demand is calculated as the percentage change in quantity demanded of Y divided by the percentage change in the price of X. Percentage change in price of X = (2.50 - 2.00) / 2.00 * 100 = +25%. Percentage change in quantity demanded of Y = (1,000 - 800) / 800 * 100 = +25%. XED = +25% / +25% = +1.0. A positive XED indicates that the two goods are substitutes.

1 mark for calculating XED as +1.0 and correctly identifying the goods as substitutes. Reject all other values or relationships.

The Price Elasticity of Supply (PES) measures the responsiveness of the quantity supplied to a change in price. Because the firm operates with almost no spare capacity (95% utilization) and suffers from skilled labor shortages, it cannot easily or quickly expand its production in the short run if the market price rises. Therefore, its supply is highly unresponsive to price changes, resulting in an inelastic supply (PES is less than 1).

1 mark for identifying that the supply is price inelastic and correctly relating it to spare capacity and labor constraints. Reject options claiming supply is elastic.

Opportunity cost is the value of the next best alternative foregone. When the economy increases its production of manufactured goods from 40 units (Combination W) to 90 units (Combination Y), the production of agricultural goods falls from 100 tonnes to 40 tonnes. The opportunity cost of this expansion is therefore 100 - 40 = 60 tonnes of agricultural goods.

1 mark for calculating the correct opportunity cost of 60 tonnes of agricultural goods. Reject other quantities or units.

Asymmetric information describes a situation where there is an imbalance of information between buyers and sellers. In the used car market, the seller typically knows the exact mechanical history and defects of the vehicle, whereas the prospective buyer cannot easily verify this quality. Because buyers lack perfect information, they are only willing to pay an average price that reflects the average risk of buying a bad car. Owners of high-quality used cars will find this average price too low and will withdraw their vehicles from the market. This process of adverse selection leaves only low-quality cars ('lemons') in the market, causing a misallocation of resources or a missing market for high-quality used cars.

1 mark for defining asymmetric information (information imbalance between buyer and seller). 1 mark for applying to the used car market (seller knows quality/defects, buyer does not). 1 mark for explaining the impact of this imbalance (buyers offer an average price, causing high-quality sellers to withdraw - adverse selection). 1 mark for explaining the market failure outcome (only low-quality cars remain, leading to a misallocation of resources or market collapse).

A maximum price is a legally established price ceiling above which landlords cannot charge. If set below the market equilibrium, it creates excess demand (a housing shortage) because the quantity demanded by tenants increases while the quantity supplied by landlords contracts. This intervention leads to government failure—a situation where government intervention results in a net welfare loss and misallocation of resources. One major reason is the emergence of unintended consequences: since landlords cannot charge market-clearing rents, they have less incentive to maintain properties, leading to a decline in housing quality, or they may convert rental properties to other uses, worsening the shortage and potentially leading to informal (black) markets where tenants pay illegal premiums.

1 mark for defining maximum price or government failure. 1 mark for explaining that a maximum price below equilibrium rent creates a shortage (quantity demanded exceeds quantity supplied). 1 mark for identifying an unintended consequence (e.g., landlords neglecting maintenance, converting properties, or black markets forming). 1 mark for linking this consequence to government failure (the policy makes tenants worse off due to poorer quality housing or lack of supply, representing a net welfare loss).

First, calculate the percentage change in quantity demanded: \(((7,200 - 8,000) / 8,000) \times 100 = -10\%\). Next, calculate the percentage change in price: \(((15 - 12) / 12) \times 100 = 25\%\). Use the PED formula: PED = % change in quantity demanded / % change in price = \(-10\% / 25\% = -0.4\). Since the absolute value of PED is less than 1, demand is price inelastic. This means the percentage decrease in quantity demanded is smaller than the percentage increase in price. Therefore, total revenue increases. This is shown by the calculations: Initial Revenue = \(12 \times 8,000 = £96,000\); New Revenue = \(15 \times 7,200 = £108,000\).

1 mark for showing correct calculation of % change in quantity demanded (-10%) or % change in price (25%). 1 mark for the correct PED value of -0.4 (accept 0.4). 1 mark for identifying that demand is price inelastic. 1 mark for explaining that total revenue increases (with or without calculation of the new revenue of £108,000 compared to £96,000) because the price rise outweighs the drop in volume.

Traditional economic theory assumes consumers are fully rational and always seek to maximize their utility. However, behavioural economics introduces the concept of bounded rationality, which argues that consumers' ability to make rational decisions is limited. This is due to three main factors: cognitive limitations (inability to process large amounts of complex price and quality data), information gaps (imperfect or incomplete information about the products), and time constraints (having to make quick decisions). Because of these bounds, consumers do not spend endless time calculating the optimal choice; instead, they 'satisfic'—they make a decision that is 'good enough' rather than utility-maximizing. This can result in purchasing lower-quality or overpriced goods, preventing them from achieving maximum utility.

1 mark for defining bounded rationality (the idea that cognitive, informational, and time limits prevent perfect decision-making). 1 mark for identifying one of these specific limits (e.g., information overload, limited computational capacity, or time pressure). 1 mark for explaining 'satisficing' (choosing an option that is satisfactory rather than optimal) or the use of heuristics (mental shortcuts). 1 mark for linking this behaviour to why utility is not maximized (consumers end up with sub-optimal outcomes, purchasing goods that do not yield the highest possible satisfaction).

Opportunity cost is defined as the benefit of the next best alternative that is foregone when a choice is made. A Production Possibility Frontier (PPF) shows the maximum combinations of two goods that an economy can produce when all resources are fully and efficiently utilized. Any point on the PPF curve represents productive efficiency. If an economy decides to increase the production of one good (for example, capital goods) and is currently producing on its PPF, it must move along the frontier. To produce more capital goods, resources must be reallocated away from the production of the other good (for example, consumer goods). The resulting decrease in the production of consumer goods is the opportunity cost of obtaining more capital goods.

1 mark for defining opportunity cost (value/benefit of the next best alternative foregone). 1 mark for describing a PPF (showing maximum output combinations when resources are fully/efficiently employed). 1 mark for explaining that a movement along the PPF requires the reallocation of resources from one product to another. 1 mark for explaining that this reallocation leads to a decrease in the output of the other good, which is the opportunity cost.

Asymmetric information represents a situation in which there is an imbalance of knowledge between buyers and sellers in a market. Usually, one party has access to superior or more detailed information than the other party. This information asymmetry hinders rational decision-making and can prevent the market from reaching an allocatively efficient outcome, often resulting in market failures such as adverse selection or moral hazard.

Award 1 mark for identifying the core concept of unequal information between parties:
- Imbalance, inequality, or asymmetry of information/knowledge between buyers and sellers (1 mark).

Award 1 mark for elaboration or development, such as:
- One party has more or better information than the other in an economic transaction (1 mark).
- Explaining that this information gap leads to market failure/misallocation of resources (1 mark).
- Providing a suitable example, such as a doctor knowing more about a medical treatment than the patient (1 mark).

Asymmetric information represents a situation in which there is an imbalance of knowledge between buyers and sellers in a market. Usually, one party has access to superior or more detailed information than the other party. This information asymmetry hinders rational decision-making and can prevent the market from reaching an allocatively efficient outcome, often resulting in market failures such as adverse selection or moral hazard.

Award 1 mark for identifying the core concept of unequal information between parties:
- Imbalance, inequality, or asymmetry of information/knowledge between buyers and sellers (1 mark).

Award 1 mark for elaboration or development, such as:
- One party has more or better information than the other in an economic transaction (1 mark).
- Explaining that this information gap leads to market failure/misallocation of resources (1 mark).
- Providing a suitable example, such as a doctor knowing more about a medical treatment than the patient (1 mark).

### Diagram Analysis
An effective maximum price (price ceiling) is set below the free-market equilibrium price (\(P_e\)).
- The original equilibrium is established where Demand (\(D\)) equals Supply (\(S\)) at price \(P_e\) and quantity \(Q_e\).
- At the maximum price \(P_{max}\), the price is legally prevented from rising to the equilibrium level.
- Consequently, the quantity demanded extends to \(Q_d\), while the quantity supplied contracts to \(Q_s\) because landlords find it less profitable to rent out apartments.
- This creates a market shortage (excess demand) equal to \(Q_d - Q_s\).
- The quantity actually traded in the market falls from \(Q_e\) to \(Q_s\).

### Application to Extract B
- The policy is introduced to curb "soaring rental prices in the capital city" of Zolaria to protect low-income tenants.
- Landlords respond by withdrawing properties from the market (shifting or contracting supply to \(Q_s\)) or "reducing maintenance", which degrades the quality of the remaining housing stock.

### Economic Analysis
- Since the price mechanism is restricted, price can no longer ration the available housing.
- Although the rent is cheaper (at \(P_{max}\)), fewer people are actually able to secure a rental home because the physical quantity supplied drops to \(Q_s\).
- This can lead to secondary market failures, such as informal black markets or non-price rationing mechanisms (e.g., long waiting lists, queueing, or landlord bias).

**Diagram (2 marks):**
- **1 mark** for a correct demand and supply diagram showing original equilibrium (\(P_e\), \(Q_e\)) and a maximum price line (\(P_{max}\)) drawn below it.
- **1 mark** for illustrating the resulting shortage/excess demand (the gap between \(Q_s\) and \(Q_d\) at \(P_{max}\)) and/or showing the contraction in quantity traded to \(Q_s\).

**Application (2 marks):**
- **1 mark** for identifying that the policy is a response to "soaring rental prices" in Zolaria to assist renters.
- **1 mark** for referencing specific landlord behavior from the extract, such as "withdrawing properties from the market" or "reducing maintenance."

**Analysis (2 marks):**
- **1 mark** for explaining how the maximum price prevents the price mechanism from allocating scarce resources, leading to chronic excess demand where \(Q_d > Q_s\).
- **1 mark** for explaining that the actual quantity of rented housing available falls from \(Q_e\) to \(Q_s\), meaning some consumers are left without housing despite the lower price.

**Identification (1 mark):**
- Public bus transport is a merit good that generates positive externalities of consumption (external benefits).

**Application (1 mark):**
- According to Extract A, increasing the use of public buses reduces traffic congestion and carbon dioxide emissions for other road users and the wider local community.

**Analysis (2 marks):**
- Consumers make decisions based purely on their marginal private benefit (\(MPB\)) and marginal private cost (\(MPC\)), ignoring the marginal external benefit (\(MEB\)) to third parties.
- Therefore, the marginal social benefit exceeds the marginal private benefit (\(MSB > MPB\)). In a free market, this leads to under-consumption of public bus services relative to the socially optimal level, resulting in a welfare loss (market failure).

**Knowledge/Understanding (1 mark):**
- Identification of positive externalities of consumption, merit goods, or the concept of social benefits exceeding private benefits (\(MSB > MPB\)).

**Application (1 mark):**
- Relevant reference to Extract A (e.g., mentions of third-party benefits such as reduced road congestion, lower air pollution, or reduced carbon emissions for non-bus users).

**Analysis (2 marks):**
- Explanation of why this leads to market failure: consumers only consider private benefits/costs (1 mark), which leads to under-consumption/allocative inefficiency/deadweight loss because the market equilibrium quantity is less than the socially optimum level (1 mark).

Introduction / Knowledge: A minimum price is a legally imposed price floor below which a good cannot be sold. To be effective, it must be set above the free-market equilibrium price. In this case, the minimum price is set at $0.50, which is significantly higher than the previous average equilibrium price of $0.20. Analysis of Positive Effects: 1) Reduction in Quantity Demanded: Raising the price from $0.20 to $0.50 creates a contraction in demand. Zentaria's Treasury estimates a 35% reduction in consumption. 2) Correcting Market Failure: Single-use plastic bottles generate negative externalities in consumption (e.g., environmental litter, marine pollution, cleanup costs). A minimum price raises the private cost to consumers, aligning it more closely with the social cost. This reduces the overconsumption of plastic, shrinking the deadweight welfare loss. Analysis of Negative Effects / Evaluation: 1) Regressive Distributional Impact: Low-income consumers spend a higher proportion of their income on basic necessities. Since municipal tap water is poor in some areas, bottled water is a necessity, making demand highly price-inelastic for these households. Thus, the policy acts as a regressive tax, worsening inequality. 2) Impact on Producers and Employment: Beverage manufacturers will face falling revenues as demand contracts. This can lead to cost-cutting measures, causing job losses in both the bottling and packaging industries. 3) Risk of Informal Markets: A high minimum price may incentivise the growth of an unregulated black market where plastic bottles are traded illegally below the legal limit.

Knowledge, Application, and Analysis (5 marks): Level 1 (1-2 marks): Identifies basic economic effects of a minimum price or negative externalities. Demonstrates limited use of the extract. Level 2 (3-5 marks): Explains how a minimum price works (preferably with a diagram showing a price floor above equilibrium, causing a contraction in demand). Applies this effectively to Zentaria (using data like the $0.50 minimum price versus $0.20, and the 35% reduction in consumption). Analyzes the positive impact on correcting market failure and external costs. Evaluation (3 marks): Level 1 (1 mark): Identifies evaluative points, such as the regressive nature of the policy or the impact on packaging jobs. Level 2 (2-3 marks): Develops evaluative points. For example, explains why the regressive impact is particularly severe due to poor municipal tap water infrastructure (necessity status of bottled water), or weighs the environmental benefits against the producer surplus losses and potential unemployment in the beverage sector.

### Diagram Description
An appropriate diagram should show:
- Vertical axis labelled 'Rent' or 'Price' (P) and horizontal axis labelled 'Quantity of Rental Housing' (Q).
- Downward-sloping Demand curve (D) and upward-sloping Supply curve (S) intersecting at the free market equilibrium price \(P_e\) and quantity \(Q_e\).
- A horizontal maximum price line \(P_{max}\) drawn strictly below the equilibrium price \(P_e\).
- At \(P_{max}\), the quantity supplied is \(Q_s\) (read from the supply curve) and the quantity demanded is \(Q_d\) (read from the demand curve).
- The horizontal distance between \(Q_s\) and \(Q_d\) represents the excess demand or housing shortage.
- The actual quantity traded falls from \(Q_e\) to \(Q_s\).

### Analysis of Economic Effects (KAA)
- **Definition**: A maximum price is a government-imposed limit on the price that landlords can charge for rent, set below the market equilibrium to make housing more affordable.
- **Impact on Consumers (Tenants)**:
- **Winners**: Tenants who secure properties at the regulated price benefit from lower housing costs, increasing their consumer surplus and disposable income for other goods.
- **Losers**: Many prospective tenants are unable to find housing due to the shortage (excess demand of \(Q_d - Q_s\)). They may be forced to commute longer distances or experience homelessness.
- **Impact on Producers (Landlords)**:
- Rental revenues and producer surplus fall. Landlords may exit the market, converting long-term rentals into short-term holiday lets or selling them, which shifts supply further to the left over time.
- **Incentives and Quality**:
- Since demand exceeds supply, landlords have little incentive to maintain or improve properties, leading to a decline in the quality of the housing stock.
- **Non-Price Rationing and Black Markets**:
- Landlords may use informal rationing (e.g., credit scores, personal bias, or illegal fees like 'key money') to choose tenants.

### Evaluation
- **Elasticity of Supply and Demand**:
- In the short run, supply is highly inelastic, meaning the reduction in quantity traded is small, and the shortage is limited.
- In the long run, both demand and supply are more price elastic. Landlords can withdraw properties and more tenants seek cheap housing, which significantly worsens the housing shortage.
- **Enforcement Costs**:
- The policy requires costly state monitoring to prevent landlords from charging illicit fees or bypassing the rent cap.
- **The Level of \(P_{max}\)**:
- If \(P_{max}\) is set only slightly below \(P_e\), the shortage will be minimal. If it is set significantly below \(P_e\), the market distortion will be severe.
- **Alternative Policies**:
- Rather than distorting market prices, governments could address the root cause of high rents by building more social housing, relaxing planning restrictions to shift supply to the right, or providing targeted housing subsidies to low-income tenants.

### Mark Breakdown (Total: 14 Marks)

#### Knowledge, Application and Analysis (KAA) - 8 Marks
- **7-8 marks (Level 3)**: Clear, fully labelled diagram showing the maximum price below equilibrium, the quantity demanded, quantity supplied, and the resulting shortage. The answer displays a highly logical and structured analysis of both positive and negative microeconomic effects on tenants and landlords, fully integrated with the diagram.
- **4-6 marks (Level 2)**: An accurate diagram with minor labelling errors or omissions. The analysis explains the shortage and price effects but lacks depth regarding broader impacts like non-price rationing or quality deterioration.
- **1-3 marks (Level 1)**: Basic identification of maximum price or a poorly drawn diagram. The analysis is superficial or lacks economic reasoning.

#### Evaluation (EV) - 6 Marks
- **5-6 marks (Level 3)**: Excellent, balanced evaluative comments. Discusses crucial factors such as short-run vs. long-run elasticities, enforcement difficulties, and alternative policies with strong economic justification.
- **3-4 marks (Level 2)**: Explains at least two evaluative points (e.g., elasticity of supply, alternative solutions) but lacks depth or logical progression.
- **1-2 marks (Level 1)**: Identifies evaluative points (e.g., 'it depends on where the price is set') without detailed economic elaboration.

### Introduction
- Define **maximum price** (price ceiling): A government-imposed limit on the price a landlord can charge for renting out a property, set below the free-market equilibrium price to protect consumers.
- State the policy's objective: To ensure that low-income households have access to affordable, secure housing.

### Diagrammatic Analysis
- Draw a microeconomic demand and supply diagram for rental housing:
- Show the initial market equilibrium at price \(P_e\) and quantity \(Q_e\).
- Show the maximum price line \(P_{max}\) drawn **below** the equilibrium price \(P_e\).
- Illustrate the resulting shortage: at \(P_{max}\), quantity demanded is \(Q_d\) and quantity supplied is \(Q_s\), leading to excess demand or a shortage of \(Q_d - Q_s\).
- Highlight the change in consumer surplus (gained by some tenants who secure housing) and producer surplus (lost by landlords).

### Analysis of Positive Microeconomic Effects
- **Improved Affordability:** Low-income tenants who manage to secure a tenancy pay lower rents, increasing their real disposable income and consumer surplus. This reduces absolute poverty and helps prevent homelessness.
- **Reduced Inequality:** It transfers economic surplus from wealthier property owners (landlords) to lower-income tenants, potentially narrowing inequality.
- **Stability:** Tenants enjoy greater security and stability, which can have positive social externalities (e.g., better educational outcomes for children due to less frequent relocation).

### Analysis of Negative Microeconomic Effects / Market Failure
- **Chronic Shortage:** Because \(P_{max} < P_e\), some landlords exit the market (shifting supply further left) or convert rental units into owner-occupied housing. Demand simultaneously rises, creating a queue.
- **Decline in Housing Quality:** Landlords experience lower profit margins or losses, reducing their incentive to spend on maintenance, repairs, and modernization. This results in the deterioration of the housing stock.
- **Black Markets and Non-Price Rationing:** Since demand exceeds supply, informal rationing mechanisms emerge (e.g., landlords demanding illegal 'key money' payments, choosing tenants based on personal bias, or favouring high-income tenants with better credit ratings, which defeats the policy's purpose).

### Evaluation
- **Elasticity of Supply:** In the **short run**, the price elasticity of supply (PES) of housing is highly inelastic (it takes time to convert or sell properties). Thus, the initial shortage is small. In the **long run**, PES is more elastic, meaning the shortage of rental accommodation becomes significantly worse as landlords divest.
- **Enforcement and Administrative Costs:** The policy requires government monitoring and legal enforcement to prevent illegal subletting or black-market payments, which carries opportunity costs for tax revenues.
- **Alternative Policies:** Contrast rent control with supply-side interventions, such as the government directly building social housing (shifting supply to the right, reducing \(P_e\) naturally) or providing housing vouchers/subsidies to low-income earners (though this might bid up market rents if supply is inelastic).
- **Conclusion / Judgment:** While rent control provides immediate relief to existing tenants, its long-term distortionary effects (housing shortages and quality decay) often worsen the housing crisis for those who cannot find a home. A combined approach of targeted income support and supply-side policies is generally more effective in achieving long-term housing affordability.

### Knowledge, Application, and Analysis (KAA) - 12 Marks
- **Level 4 (10–12 marks):** Clear, precise economic concepts are used throughout. The diagram is fully correct, clearly labelled, showing \(P_{max}\), \(Q_s\), \(Q_d\), and the resulting shortage. The analysis is deep, logical, and addresses both positive and negative microeconomic consequences of maximum prices on rent.
- **Level 3 (7–9 marks):** Good understanding of maximum prices and rent controls. The diagram is mostly correct with minor labelling errors. Analysis covers key impacts (e.g., shortage, quality deterioration, lower prices) but may lack depth in explaining some transmission mechanisms.
- **Level 2 (4–6 marks):** Basic understanding of a maximum price. Diagram is either missing or contains significant errors. Analysis is descriptive rather than analytical, with limited focus on the rental market context.
- **Level 1 (1–3 marks):** Identifies basic definitions (maximum price, shortage) but lacks application to the housing market or formal analysis.

### Evaluation - 8 Marks
- **Level 3 (7–8 marks):** Offers a balanced, high-quality evaluative discussion. Directly addresses the distinction between short-run and long-run impacts (elasticity). Suggests viable alternative policies with comparison. Concludes with a reasoned judgment on the overall effectiveness of the policy.
- **Level 2 (4–6 marks):** Some evaluative points are made (e.g., mentioning that landlords might stop maintaining properties or that a black market might form), but points are not fully developed or lack a coherent final judgment.
- **Level 1 (1–3 marks):** Basic, generic evaluative statements (e.g., 'it depends on how low the price is set') with no real development or structural balance.