Government Intervention

Indirect taxes, subsidies, maximum & minimum prices, tradeable permits, regulation, and state provision

SPEC 1.4 • MARKET FAILURE & INTERVENTION

Why Governments Intervene

Markets fail when the free market equilibrium output differs from the socially optimal output. Governments intervene to correct market failure and move output towards Q*.

The 6 Tools on the Spec — Learn All of Them

Indirect taxation — specific and ad valorem taxes

Subsidies — payment to producers to increase output

Maximum prices (price ceiling) — set below equilibrium

Minimum prices (price floor) — set above equilibrium

Tradeable pollution permits — market-based quantity control

Regulation, state provision, information provision

Chain of Reasoning

Market failure identified → specific tool chosen → mechanism explained → output moves from Qm toward Q* → welfare gain assessed. Always complete the chain.

Indirect Taxation — Two Types

Specific Tax

A fixed amount per unit of output. The supply curve shifts left by a parallel amount equal to the tax. Example: fuel duty (pence per litre).

Ad Valorem Tax

A percentage of the price of the good. The supply curve pivots/rotates — the wedge is larger at higher prices. Example: VAT (20%).

Examiner Alert — October 2020 P1 Q1

This diagram appeared in the actual exam. A minority drew the shift as if it were an ad valorem tax and lost a mark. Specific tax = parallel shift. Ad valorem = rotating shift. State which type before drawing.

Diagram Required for Top Marks

A tax question without the supply shift, consumer incidence, producer incidence, AND government revenue rectangle cannot access the highest mark band.

Tax Incidence Diagram — Step by Step

Draw this diagram in 6 steps. Every label must be present to score full marks.

Must Show

Tax Incidence & Elasticity

Who bears the tax depends entirely on the relative elasticities of demand and supply.

Chain of Reasoning — Elasticity & Incidence

Inelastic demand (e.g. cigarettes, petrol) → consumers cannot easily reduce Qd → consumer incidence is large → tax raises revenue but has limited effect on quantity consumed → market failure only partially corrected.

ScenarioWho Pays More?Exam Implication

Inelastic demand, elastic supplyConsumers bear mostTax raises revenue; small quantity reduction

Elastic demand, inelastic supplyProducers bear mostLarge quantity reduction; less revenue

Equal elasticitiesSplit 50/50Balanced outcome

AO4 Evaluation: consider…

If demand is inelastic, a corrective (Pigouvian) tax may raise significant revenue but fail to achieve the socially optimal output Q* — the market failure persists. This limits the effectiveness of the tax as a policy tool.

Subsidies

Subsidy

A payment by the government to producers to reduce their costs of production and increase output towards the socially optimal level Q*. Supply curve shifts right (downward).

Chain of reasoning: Government grants subsidy → costs of production fall → supply shifts right to S−sub → price falls from P₁ to P₂ → quantity rises from Q₁ toward Q* → under-provision of merit good corrected.

Must Show

Total subsidy cost = (P₁ − P₂) × Q₂ (the full rectangle). Consumer benefit = price fall × Q₂. Producer benefit = the remainder. Both must be shown separately on the diagram.

Maximum & Minimum Prices

The most common source of student errors on price controls is confusing which creates a shortage and which creates a surplus. Here is the definitive distinction.

Maximum Price (Price Ceiling)

A legally imposed price set BELOW the equilibrium price. Makes a good more affordable. Result: excess demand (shortage). Examples: rent controls, energy price caps.

Minimum Price (Price Floor)

A legally imposed price set ABOVE the equilibrium price. Guarantees producers a minimum income. Result: excess supply (surplus). Examples: minimum wage, minimum alcohol price.

Examiner Alert — Most Common Error

Students frequently draw a maximum price above the equilibrium (which has no effect) or confuse the direction of the shortage/surplus. Max price BELOW equilibrium = shortage. Min price ABOVE equilibrium = surplus. Repeat this until it is automatic.

Price Control Diagrams

Apply to Context

Minimum alcohol price (e.g. 50p/unit in Scotland): set above equilibrium → reduces Qd of cheap alcohol → aims to reduce negative externalities of alcohol. Evaluate: inelastic demand for alcohol limits quantity reduction.

Tradeable Pollution Permits

Tradeable Pollution Permit

Licences that allow firms to emit a certain quantity of pollution. Firms can buy and sell these permits on a market. The government sets a total cap on pollution and issues permits up to that cap.

How They Work — Chain of Reasoning

Government sets total cap → issues permits (e.g. carbon credits) → firms that can reduce emissions cheaply sell spare permits → firms that cannot reduce cheaply buy permits → total emissions stay within cap → market mechanism determines least-cost path to Q*.

High-Value Evaluation — Carbon Tax vs ETS

Carbon tax: price certainty but not quantity certainty — you know the tax rate, not how much pollution falls. ETS (permits): quantity certainty — cap is fixed — but not price certainty — permit price fluctuates. For climate targets, quantity certainty matters most. This is why the UK and EU use emissions trading schemes over pure carbon taxes.

Regulation, State Provision & Information

ToolMechanismAdvantageLimitation

RegulationLegally enforceable rules (emission standards, advertising bans, safety laws)Certainty of outcome — compliance is mandatoryCompliance costs passed to consumers; regulatory capture risk

State ProvisionGovernment directly supplies goods free at point of use (NHS, schools)Corrects underprovision of merit goods; overcomes free rider problemHigh opportunity cost; potential inefficiency vs private provision

Information ProvisionHealth warnings, calorie labels, financial education campaignsLeast coercive; respects consumer choiceEffectiveness depends on whether people change behaviour

AO4 Evaluation: consider…

Regulatory capture — when the regulatory body ends up serving producer interests rather than consumer interests, due to lobbying or the revolving door of personnel between firms and regulators. Example: Ofgem's oversight of energy companies. This is a top-mark differentiation point.

AO4 Evaluation Toolkit

For any government intervention essay, deploy these five evaluation angles. Each should be developed with a chain of reasoning.

1. Elasticity

If demand is inelastic (e.g. petrol, cigarettes), a tax raises revenue but has limited effect on quantity. The market failure persists even with the tax — limited effectiveness as a corrective tool.

2. Difficulty of Setting the Optimal Rate

The external cost is extremely difficult to measure accurately. A Pigouvian tax set too low under-corrects; set too high, output falls below Q* creating a new inefficiency. Information failure undermines the policy.

3. Unintended Consequences

Maximum price → black markets may emerge. Minimum price → excess supply may require government to purchase surplus (EU butter mountains). Regulation → compliance costs reduce competitiveness.

4. Government Failure Risk

If intervention leads to a net welfare loss greater than the original market failure, it constitutes government failure. Must weigh the welfare gain from correcting market failure against the deadweight loss created by the intervention.

5. Long-Run vs Short-Run

A carbon tax may be ineffective short-run (inelastic demand for fossil fuels) but more effective long-run as firms invest in cleaner technology. Time horizon matters for evaluation conclusions.

Practice Question 1 — 4 Marks

Fuel duty is a specific tax of 52.95p per litre charged on petrol.

Draw a supply and demand diagram to show the incidence of this specific tax on consumers and producers. (4 marks)

1

Draw axes labelled Price (vertical) and Quantity (horizontal). Draw downward sloping D and upward sloping S intersecting at P₁, Q₁.

2

State it is a specific tax, therefore draw S+tax as a parallel shift left by the tax amount (52.95p). Label the new curve S+tax or S₂.

3

Mark new equilibrium: P₂ (consumer price, higher) and Q₂ (quantity, lower). Mark P₃ where S meets Q₂ (producer price, lower than P₁).

4

Label: Consumer incidence = P₂ − P₁. Label: Producer incidence = P₁ − P₃. Show the total tax = P₂ − P₃. All labels must be present for full marks.

Practice Question 2 — 10 Marks

Assess the effectiveness of a maximum price as a way of making housing more affordable.(10 marks)

KAA

Define maximum price: a legally imposed price set BELOW equilibrium to make a good more affordable. At rent cap Pm < Pe: Qd > Qs → excess demand (shortage of housing). Chain: lower rent → more households can afford housing → positive income redistribution → addresses affordability market failure.

AO4 1

Elasticity of supply: housing supply is inelastic in the short run (construction takes time). The shortage created by rent control may be large. Landlords may withdraw properties from the rental market, further reducing Qs and worsening the shortage.

AO4 2

Unintended consequences: rent controls may lead to a black market at prices above the cap, or landlords may allow property quality to deteriorate. Long-run supply falls as developers reduce investment — the policy worsens the problem it aimed to solve.

AO4 3

Alternative policies: a subsidy to housing construction shifts S right, raising quantity without creating a shortage. Planning reform to increase housing supply may be more effective long-run. Comparison demonstrates evaluative range.

Judgement

A maximum price may temporarily improve affordability for existing tenants but is likely to reduce long-run housing supply due to inelastic supply response and landlord exit. Supply-side policies are likely more effective at addressing the root cause.

Summary

Key Definitions — Word for Word

TermDefinition

Specific taxA fixed tax per unit of output; supply shifts left by a parallel amount equal to the tax

Ad valorem taxA percentage tax on the value of output; supply curve pivots/rotates

SubsidyA payment by the government to producers to reduce their costs of production and increase output

Maximum priceA legally imposed price set BELOW equilibrium; results in excess demand (shortage)

Minimum priceA legally imposed price set ABOVE equilibrium; results in excess supply (surplus)

Tradeable pollution permitLicences allowing firms to emit a certain quantity of pollution; can be bought and sold on a market

Diagrams — Always Required

Tax: parallel shift, P₂ consumer, P₃ producer, DWL

Subsidy: rightward shift, consumer + producer benefit

Max price: horizontal line BELOW Pe → shortage

Min price: horizontal line ABOVE Pe → surplus

Top Evaluation Points

Elasticity determines incidence and effectiveness

Difficulty measuring optimal tax/subsidy rate

Unintended consequences (black markets, landlord exit)

Regulatory capture limits regulation effectiveness

Government failure risk — weigh against market failure

Exam Tip — Mark Band Access

A response discussing taxes without the diagram, incidence split, and elasticity analysis cannot access Level 3. An evaluation that identifies only one side of an argument cannot reach Level 4. Always structure: KAA → evidence/diagram → two-sided evaluation → justified conclusion.