Negative externalities from growth
A negative externality arises when the social cost of an activity exceeds its private cost. Growth means more output, transport and resource use, imposing environmental costs: air and water pollution, noise, visual pollution and land degradation. Because polluters do not pay these costs, the free market overproduces such goods — a market failure that justifies government intervention.
The growth–environment trade-off
Economic growth (rising real GDP (gross domestic product)) raises living standards, but the activity behind it intensifies pollution. The trade-off: regulations and green taxes protect the environment yet raise firms' costs, slowing growth; while growth at all costs risks depletion and climate change. Sustainable development — meeting present needs without compromising future generations — tries to reconcile the two.
Four policy instruments
Four tools internalise the externality. Regulation: legal emission limits, fines for breaches — certain but costly to enforce. Environmental (Pigouvian) tax: a tax equal to the external cost raises price and cuts output — but hard to set exactly. Tradeable permits: a cap on total pollution, traded between firms — the market finds the cheapest cuts. Subsidies: fund green alternatives to polluting activity.
Drawn from real examiner reports.
Trade-off is not the damage mechanism
Asked for a reason there is a trade-off between growth and the environment, many describe how growth damages it — a different question, scoring 0. A trade-off means pursuing one goal (higher GDP) makes another (clean air) harder — e.g. environmental rules raise firms' costs. Show the tension, not a list of harms.
November 2024 Paper 2, Q2(e): examiner report notes most candidates answered the wrong question, explaining environmental damage rather than the trade-off itself — scored 0 marks.
Describe: name it, then develop it
On a Describe, naming an activity earns the identification mark but not the development mark. You must (1) state a valid way it harms the environment AND (2) develop it — e.g. road freight burns fossil fuels → emissions → air pollution. 'Mining damages the environment' alone earns one mark, not two.
June 2024 Paper 2, Q1(d): examiner reports that stating an activity was insufficient — candidates had to explain how or why the environment was harmed to earn the development mark.
No evaluation on an Analyse
Analyse questions reward AO1 (knowledge), AO2 (application) and AO3 (analysis) only — no AO4 (evaluation). Arguing 'regulation may fail because firms evade it' earns nothing here. Instead sustain a one-sided chain: regulation raises costs → output falls → emissions fall → the externality shrinks. Save counter-arguments for Assess/Evaluate.
November 2024 Paper 2, Q3(d): well-answered 6-mark Analyse on regulations — candidates who developed one-sided chains of reasoning reached level 2.
The externality falls on third parties
A negative externality is a cost borne by third parties who did not produce or consume the good — not a cost to the firm. Firms weigh only private costs and benefits, so external costs are ignored and the market overproduces — output settles above the socially optimal quantity. Calling the firm's own wage or fuel bill an externality misses the point.
Sustainable development is not zero growth
Sustainable development means meeting present needs without compromising future generations — not stopping growth. It allows growth that uses renewables no faster than they regenerate and keeps pollution within nature's absorptive capacity. Saying sustainability requires zero growth is wrong: the aim is to decouple growth from environmental damage.
Permits cap quantity; taxes set a price
Do not blur the two market tools. A tradeable permit scheme fixes the quantity of pollution (a cap) and lets the market price the permits. An environmental tax fixes the price per unit of pollution and lets firms choose the quantity. Both internalise the externality, but one fixes the amount and the other the price.
Evaluate: two sides, then a real judgement
A 12-mark Evaluate needs all four AOs. Scaffold: define → analyse one side (growth → emissions → pollution) → analyse the other (green tech and taxes can decouple growth) → supported judgement. The conclusion must add something new, not repeat earlier points.
Label market and optimal output
For an externality diagram, mark both quantities: the market output and the lower socially optimal output. Show the gap between them as the welfare loss, and reference it in your writing. An unlabelled or unmentioned diagram earns nothing.
Trade-off answers: show the tension
For a trade-off question, name both objectives (higher GDP (gross domestic product) versus a cleaner environment) and explain why gaining one costs the other: green rules raise firms' costs and slow growth. State the tension — listing harms answers a different question.
Weigh each policy: strength and limit
When evaluating an environmental policy, pair a strength with a limitation: regulation gives certainty but is costly to enforce; a green tax signals the true cost but is hard to set exactly. Balancing both sides earns the AO4 (assessment objective 4) marks.
Economic growth is a sustained increase in real GDP (gross domestic product) — the total value of goods and services produced in an economy. Growth raises living standards but creates environmental pressures.
Growth requires more inputs (land, labour, capital, energy) and generates more outputs, including unwanted by-products:
| Type of pollution | Example |
|---|---|
| Air pollution | Factory smokestacks, vehicle exhausts releasing CO₂ and particulates |
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