Market Failure & Externalities

A 4-mark "how can the government correct a negative externality" question usually rewards two clearly distinct policies, each with a short explanation.

Indirect taxation (Pigouvian tax)

The government levies an indirect tax on the producer or consumer of the good. If the tax is set equal to the external cost per unit, it forces the producer or consumer to internalise the externality: their private cost now matches the social cost.

On a diagram, the tax shifts the supply curve to the left. The equilibrium price rises and the equilibrium quantity falls, bringing output back toward the socially optimal level.

A higher price funded by the tax also raises government revenue, which can be used to fund the clean-up or to compensate affected third parties.

A complication tested at IGCSE: the incidence of the tax (who actually pays it) depends on price elasticity of demand. For an inelastic good (cigarettes, petrol), most of the tax is passed on to the consumer as higher prices, because demand barely falls. For an elastic good, most of the tax is absorbed by the producer (the firm has to swallow the cost or risk losing too many sales).

Regulation, bans, and standards

The government can use laws to restrict the harmful activity directly. Examples:

• Emission caps for industrial plants.
• Bans on the sale of certain pesticides.
• A minimum legal age for buying alcohol or tobacco.
• Smoke-free zones in public buildings.

Regulation works by setting a maximum quantity or by removing the activity altogether, rather than relying on price. It is most effective when the external cost is severe or when monitoring individual emissions is expensive.

Tradable pollution permits

The government issues a fixed number of permits, each allowing the holder to emit a specified amount of pollution. Firms that can cut pollution cheaply do so and sell their unused permits; firms that cannot cut pollution cheaply buy more permits. This creates a market price for pollution and reduces overall emissions at the lowest total cost.

Information campaigns and education

Some externalities arise from poor information. Government advertising campaigns, warning labels and school education can change consumer behaviour without changing the price (e.g. anti-smoking adverts; warnings on cigarette packets; school programmes on healthy eating).

Minimum prices

The government can set a minimum price above the free-market price to discourage consumption of a demerit good (e.g. minimum unit pricing for alcohol). The higher legal price reduces quantity demanded.