IAL AS Economics · Unit 1 · WEC11/01
Markets
in Action
Scarcity, PPF, demand & supply analysis, elasticities, market failure, externalities, public goods, information gaps, and government intervention — the complete Unit 1 toolkit.
1.3.1
Introductory Concepts — Scarcity, PPF & Economic Systems
The Nature of Economics
Economics as a social science: Studies human behaviour regarding the allocation of scarce resources. Unlike natural sciences, economics cannot conduct controlled experiments — human behaviour is unpredictable and context-dependent. Economists instead build models based on simplifying assumptions to generate testable predictions.
Ceteris paribus ("all other things being equal"): The assumption that all other variables are held constant when examining the relationship between two variables. E.g., when drawing a demand curve, we assume income, tastes, and prices of related goods are unchanged.
Positive statements: Objective, factual claims that can be tested against evidence. E.g., "A minimum wage of £9.50 reduces employment by 3%."
Normative statements: Value judgements — subjective opinions about what should happen. E.g., "The government ought to redistribute income more aggressively." Cannot be proved true or false.
Normative statements: Value judgements — subjective opinions about what should happen. E.g., "The government ought to redistribute income more aggressively." Cannot be proved true or false.
Examiners often ask you to distinguish positive from normative. Key test: can the statement be empirically verified? If it contains "should," "ought," or an implicit value judgement, it's normative.
Scarcity and Opportunity Cost
Scarcity: The fundamental economic problem — unlimited human wants but finite resources (land, labour, capital, enterprise). Scarcity forces choice.
Opportunity cost: The next best alternative forgone when a choice is made. E.g., building a new hospital means not building 3 schools with the same budget — the opportunity cost is those 3 schools.
- Renewable resources: Replenished naturally — wind, solar, fish stocks (if managed). Not permanently depleted.
- Non-renewable resources: Finite stock — oil, coal, natural gas. Extraction permanently reduces available supply.
- Free goods: Not scarce — no opportunity cost (e.g., air, sunlight). No economic decision needed.
- Economic goods: Scarce — involve opportunity cost and require allocation decisions.
Production Possibility Frontiers (PPF)
PPF: A curve showing the maximum combinations of two goods an economy can produce when all resources are fully and efficiently employed. Points inside = inefficient; points on = productively efficient; points outside = currently unattainable.
| Point on PPF | Meaning | Example |
|---|---|---|
| On the PPF | Productively efficient — full resource utilisation | All workers employed, all capital used |
| Inside the PPF | Inefficient — underemployment of resources | Recession, unemployment |
| Outside the PPF | Currently unattainable — beyond current capacity | Would require more resources or technology |
| Shift outward | Economic growth — more resources or better technology | New capital investment, improved education |
| Movement along | More of one good means less of another (opportunity cost) | More consumer goods → fewer capital goods |
Capital vs consumer goods: Producing more capital goods (machines, infrastructure) now means fewer consumer goods now, but shifts the PPF outward in the future — increasing long-run productive potential.
The PPF is a staple diagram question. Always: label both axes with specific goods, show where current production lies, label efficient/inefficient points. If asked about growth, show the outward shift and explain what caused it (investment, technology, immigration of skilled workers).
Specialisation, Division of Labour & Financial Markets
Division of labour (Adam Smith, Wealth of Nations, 1776): Breaking production into specialised tasks — workers become highly skilled at their specific task, reducing time wasted switching activities. Smith's pin factory example: 10 workers producing ~48,000 pins/day through division of labour vs ~200 individually.
✓ Advantages of specialisation
- Higher productivity — workers master one task
- Economies of scale at firm/national level
- Comparative advantage in international trade
- Learning by doing — skill accumulation
✗ Disadvantages of specialisation
- Monotony — boredom reduces motivation
- Structural unemployment if skill becomes obsolete
- Interdependence risk — breakdown affects whole chain
- Less flexibility — narrow skills base
Functions of money: Medium of exchange (avoids double coincidence of wants problem of barter); store of value (purchasing power held over time); measure of value (common unit for comparison); method of deferred payment (credit/debt transactions possible).
Role of financial markets: Facilitate saving and investment; channel funds from savers to borrowers; provide forward/futures markets (manage price risk); equity markets (businesses raise capital by selling shares).
Economic Systems
| System | Resource allocation | Key advantage | Key problem |
|---|---|---|---|
| Free market | Price mechanism | Allocative efficiency; incentives; innovation | Market failures; inequality; public goods underprovided |
| Command economy | Central government planning | Can prioritise equity/strategic goods; no unemployment in theory | Information problem (Hayek); incentive problem; inefficiency |
| Mixed economy | Both — market with state intervention | Addresses market failures while preserving incentives | Government failure risk; difficult to find right balance |
1.3.2
Consumer Behaviour, Demand & Elasticities
Rational Decision Making & Behavioural Economics
Rational consumer: Traditional assumption — consumers aim to maximise utility (satisfaction) from available income. Each additional unit consumed provides diminishing marginal utility, explaining the downward-sloping demand curve.
However, behavioural economics (Kahneman & Tversky) shows consumers often deviate from rationality:
| Bias/Behaviour | Explanation | Example |
|---|---|---|
| Herding | Following what others do regardless of own preferences | Buying a stock because others are buying |
| Habitual behaviour | Repeating past choices without reassessing | Brand loyalty to a product |
| Inertia | Sticking with default option due to effort of switching | Not switching energy supplier despite cheaper options |
| Poor computational skills | Difficulty evaluating complex price comparisons | Missing a better mortgage deal |
| Need to feel valued | Paying premium for perceived status or identity | Buying designer goods |
| Framing & anchoring | Decision affected by how information is presented | "90% fat-free" vs "10% fat" — same product |
Behavioural economics is heavily tested in AS Unit 1. For any question about why consumers don't behave rationally, pick 2–3 specific biases, give a real-world example for each, and explain why each one causes a welfare-reducing outcome.
The Demand Curve
Demand: The quantity of a good consumers are willing and able to purchase at each price over a given time period, ceteris paribus. The demand curve slopes downward — higher price → lower quantity demanded (law of demand), reflecting diminishing marginal utility.
Movement along vs shift of demand curve:
- Movement along: Caused only by a change in the good's own price. Extension (price falls) or contraction (price rises).
- Shift of the curve: Caused by any non-price factor → new demand curve at every price level.
Factors that Shift Demand (INCATS)
| Factor | Direction | Example |
|---|---|---|
| Income (normal good) | ↑ income → rightward shift D | Rising wages → more restaurant meals |
| Income (inferior good) | ↑ income → leftward shift D | Rising wages → less instant noodles |
| Price of substitute | ↑ substitute price → rightward shift D | Pepsi price rises → more Coca-Cola demanded |
| Price of complement | ↑ complement price → leftward shift D | Petrol price rises → fewer cars demanded |
| Advertising | More advertising → rightward shift D | Nike campaign increases trainers demand |
| Tastes/fashions | Change in preferences shifts D | Health awareness → less demand for sugar |
| Population size/age | Larger/younger population may shift D | Baby boom → more demand for schools |
Price Elasticity of Demand (PED)
PED: Measures the responsiveness of quantity demanded to a change in price, ceteris paribus.
PED = % change in Quantity Demanded ÷ % change in Price — always negative (inverse relationship); we usually quote absolute value
| Value | Type | What it means |
|---|---|---|
| |PED| = 0 | Perfectly inelastic | Quantity doesn't change with price (e.g., insulin for diabetics) |
| 0 < |PED| < 1 | Price inelastic | Quantity changes by less than price change (necessities, addictive goods) |
| |PED| = 1 | Unitary elastic | Total revenue unchanged when price changes |
| |PED| > 1 | Price elastic | Quantity changes by more than price (luxuries, substitutes available) |
| |PED| = ∞ | Perfectly elastic | Consumers buy any quantity at current price; none at higher price |
Factors Determining PED
- Availability of substitutes: More substitutes → more elastic (consumers switch easily)
- Branding: Strong brand loyalty → more inelastic (consumers won't switch)
- Percentage of income: Small % of income → inelastic (e.g., salt); large % → elastic (e.g., car)
- Addictiveness: Addictive goods → inelastic (cigarettes, alcohol)
- Durability: Durable goods → more elastic (consumers can delay purchase)
- Time period: Short-run more inelastic; long-run more elastic (habits change, alternatives develop)
PED and Total Revenue (TR)
Total Revenue = Price × Quantity Demanded
| PED | Price rise effect on TR | Price fall effect on TR |
|---|---|---|
| Elastic (|PED|>1) | TR falls (big Q fall outweighs P rise) | TR rises (big Q rise outweighs P fall) |
| Inelastic (|PED|<1) | TR rises (small Q fall, big P gain) | TR falls (small Q gain, big P loss) |
| Unitary (|PED|=1) | TR unchanged | TR unchanged |
The PED–TR relationship is examined every year. The key logic: elastic demand → consumers very responsive to price → raising price loses more revenue from volume than gained from price. Inelastic → opposite. Always give a numerical example to back it up.
Income Elasticity of Demand (YED)
YED = % change in Quantity Demanded ÷ % change in Income
- YED > 0: Normal good — demand rises with income (most goods)
- YED > 1: Luxury/income elastic — demand rises faster than income (e.g., holidays, premium cars)
- 0 < YED < 1: Necessity/income inelastic — demand rises slower than income (e.g., bread, bus journeys)
- YED < 0: Inferior good — demand falls as income rises (e.g., own-brand supermarket goods, bus travel when car affordable)
Cross Elasticity of Demand (XED)
XED = % change in QD of Good A ÷ % change in Price of Good B
- XED > 0: Substitutes — goods compete (Pepsi and Coke). Stronger substitutes → higher positive XED
- XED < 0: Complements — goods used together (petrol and cars). Stronger complements → more negative XED
- XED = 0: Unrelated goods — changes in B's price don't affect A's demand
For significance of elasticities — always state one implication for each stakeholder. Firms: use PED to set prices (inelastic → raise price, elastic → cut price to gain market share). Government: tax inelastic goods (tobacco, fuel) for revenue without large demand fall. Consumers: elastic demand means more price-sensitive buying decisions. YED tells businesses how to plan across the economic cycle.
1.3.3
Supply & Price Elasticity of Supply
The Supply Curve
Supply: The quantity of a good producers are willing and able to offer for sale at each price over a given time period, ceteris paribus. Supply curve slopes upward — higher price → more supplied (more profitable to produce; existing firms expand; new firms enter).
Movement vs shift: Movement along — only own price changes. Shift — any other factor changes supply at all prices.
Factors Shifting Supply (TINSG)
| Factor | Direction | Example |
|---|---|---|
| Technology | Better tech → rightward shift S (lower unit costs) | Automation in car manufacturing |
| Input costs | Higher wages/materials → leftward shift S | Oil price spike raises transport costs |
| Indirect taxes | Tax → leftward shift S (treated as a cost) | Excise duty on alcohol |
| Subsidies | Subsidy → rightward shift S (reduces cost) | Government subsidy to renewable energy firms |
| Natural disasters/weather | Supply shock → leftward shift S | Drought → less wheat supply |
| Number of producers | More firms → rightward shift S | New entrants into electric vehicle market |
Price Elasticity of Supply (PES)
PES: Measures the responsiveness of quantity supplied to a change in price, ceteris paribus.
PES = % change in Quantity Supplied ÷ % change in Price — always positive (positive relationship)
| PES Value | Type | Example |
|---|---|---|
| PES = 0 | Perfectly inelastic | Scarce art, fixed land supply |
| 0 < PES < 1 | Inelastic | Agricultural goods (growing takes time) |
| PES = 1 | Unitary elastic | — |
| PES > 1 | Elastic | Manufactured goods with idle capacity |
| PES = ∞ | Perfectly elastic | Theoretical — any price rise causes infinite supply response |
Factors Determining PES
- Time period: Short run → inelastic (can't change fixed factors); long run → more elastic
- Availability of stocks/perishability: Storable goods → elastic (can release stock); perishable goods → inelastic
- Mobility of factors of production: Mobile factors → more elastic (can quickly scale up)
- Spare capacity: If capacity exists → elastic (easy to increase output). At full capacity → inelastic
- Legal constraints: Planning permission, quotas → reduce PES
Short run vs long run PES is key. In the short run, at least one factor of production is fixed (usually capital), so supply is relatively inelastic. In the long run, all factors are variable, so supply is more elastic. This distinction explains why price spikes after supply shocks are greater in the short run and dampen over time.
1.3.4
Price Determination — Equilibrium, Surplus & the Price Mechanism
Market Equilibrium
Equilibrium: The price at which quantity demanded equals quantity supplied — no tendency for price to change. Determined by intersection of D and S curves.
Excess demand (shortage): P below equilibrium → Qd > Qs → upward pressure on price → price rises until equilibrium restored.
Excess supply (surplus): P above equilibrium → Qs > Qd → downward pressure on price → price falls until equilibrium restored.
Market forces automatically eliminate disequilibrium — this self-correcting mechanism is a key strength of the free market.
Consumer and Producer Surplus
Consumer surplus: The difference between what a consumer is willing to pay and what they actually pay. The area below the demand curve and above the equilibrium price.
Producer surplus: The difference between the price a producer receives and the minimum price they would accept. The area above the supply curve and below the equilibrium price.
Significance: Total welfare = consumer surplus + producer surplus. Market efficiency maximised where this sum is greatest — at free market equilibrium. Price controls (max/min prices) or taxes that reduce equilibrium quantity create deadweight welfare losses.
Functions of the Price Mechanism
| Function | How it works | Example |
|---|---|---|
| Signalling | Price changes transmit information about scarcity/abundance | Rising wheat price signals shortage → farmers grow more |
| Incentive | Higher prices encourage more production; lower prices discourage | High oil profits → exploration of new reserves |
| Rationing | Limited goods allocated to those willing to pay most | House prices ration limited housing among buyers |
Indirect Taxes and Subsidies
Specific tax: Fixed amount per unit (e.g., 80p per litre of petrol). Shifts supply curve leftward by the tax amount — parallel shift.
Ad valorem tax: Percentage of price (e.g., 20% VAT). Shifts supply curve leftward by increasing proportion at higher prices — wedge/pivoted shift.
Tax incidence: Who actually bears the burden of the tax. If demand is inelastic → most of the tax falls on consumers (price rises by nearly the full tax amount). If demand is elastic → most falls on producers (can't raise price much without losing customers).
Subsidy: Government payment to producers → shifts supply curve rightward → lower equilibrium price → higher equilibrium quantity. Benefits shared between producers (higher profits) and consumers (lower prices) — split depends on elasticities.
Tax incidence diagrams are a favourite question. Key: the less elastic side of the market bears more of the tax burden. Draw the leftward shift of supply, show the new higher price for consumers and lower net price for producers, shade the tax revenue rectangle and explain who bears the larger portion.
1.3.5
Market Failure — Externalities, Public Goods & Information
Sources of Market Failure
Market failure: Occurs when the free market allocates resources inefficiently — too much or too little of a good is produced relative to the socially optimal level, creating a welfare loss.
Main Sources
- Externalities: Costs/benefits falling on third parties not party to the transaction
- Public goods: Free-rider problem prevents private provision
- Imperfect information: Asymmetric information leads to under/over-consumption
- Moral hazard: Insured parties take greater risks than they would without insurance
- Speculation and market bubbles: Asset prices diverge from fundamental values
Externalities
Externality: A cost or benefit experienced by a third party as a result of a transaction between a buyer and seller, which is not reflected in the market price. Creates a divergence between private and social costs/benefits.
Key terms:
- Private cost/benefit: Cost/benefit to the direct parties (buyer and seller)
- External cost/benefit: Cost/benefit to third parties (not involved in transaction)
- Social cost = Private cost + External cost
- Social benefit = Private benefit + External benefit
| Type | Effect | Market outcome | Example |
|---|---|---|---|
| Negative externality of production | MSC > MPC | Over-produced relative to socially optimal Q* | Factory pollution, carbon emissions from manufacturing |
| Negative externality of consumption | MSC > MPC (via consumption) | Over-consumed relative to Q* | Alcohol, cigarettes, congestion from car use |
| Positive externality of consumption | MSB > MPB | Under-consumed relative to Q* | Education, vaccines — consumer gains less than society |
| Positive externality of production | MSB > MPB | Under-produced relative to Q* | Employer training — benefits other firms who hire trained workers |
Welfare loss: The area between the market quantity and the socially optimal quantity, representing the net loss to society. For negative externalities: market produces too much → welfare loss equals triangle between Qmarket and Q*. For positive externalities: market produces too little → similar welfare loss triangle.
Externality diagrams are the most important Unit 1 diagrams. You must know: (1) for negative externality of production — MPC shifts right to give MSC, Qmarket too high, draw deadweight loss triangle; (2) for positive externality of consumption — MPB shifts right to give MSB, Qmarket too low. Always label the diagrams fully: P, Q, MPC, MSC (or MPB, MSB), Qmarket, Q*, and the welfare loss area.
Public Goods
Private good: Rival (one person's consumption reduces availability for others) and excludable (possible to prevent non-payers from accessing). E.g., a sandwich, a car, a concert ticket.
Public good: Non-rival (one person's consumption does not reduce availability) AND non-excludable (impossible to prevent free-riders from benefiting). E.g., national defence, lighthouses, street lighting, flood defences.
Free-rider problem: Since non-payers cannot be excluded from a public good, rational individuals will not pay voluntarily — they "free-ride." If everyone free-rides, the good is not provided at all by the private sector → market failure. State provision required.
Quasi-public goods: Display one but not both characteristics (e.g., roads — non-excludable but congested = rival at capacity). May be provided privately (toll roads) or publicly.
The distinction between non-rival and non-excludable is the entire basis for public goods questions. Define both precisely, give an example, then explain the free-rider problem and why this leads to under-provision. Common mistake: saying a public good is "provided by the government" — this is not the definition. It is non-rival AND non-excludable.
Imperfect Information
Asymmetric information: One party to a transaction has more information than the other. This distorts market decisions and causes misallocation of resources.
| Context | Information problem | Market failure |
|---|---|---|
| Healthcare | Patients cannot assess quality of treatment; doctors know more | Under-consumption; supplier-induced demand |
| Education | Individuals may underestimate long-run returns to education | Under-investment in human capital |
| Pensions | Workers don't understand compound interest/long-run need | Under-saving for retirement |
| Insurance (adverse selection) | High-risk buyers know more about risk than insurer | Adverse selection — only high-risk people buy insurance; market fails |
Moral Hazard
Moral hazard: When having insurance or protection against risk causes a person to take greater risks than they would otherwise — because the cost of failure falls on someone else (the insurer).
- Insurance: Insured driver may drive less carefully; insured homeowner may invest less in security
- Banking: Banks with government bailout guarantee ("too big to fail") take excessive risks — privatise gains, socialise losses. 2008 financial crisis: banks took on excessive mortgage-backed securities risk knowing systemic importance meant bailout was likely
Speculation and Market Bubbles
Market bubble: When asset prices rise far above their fundamental value driven by speculative demand — buyers expect prices to keep rising and buy to profit from future price rises rather than underlying value. Eventually the bubble bursts when reality reasserts itself.
- Housing: 2007–08 US subprime housing bubble — rising prices encouraged speculative buying → bank lending surged → bubble burst → financial crisis → recession
- Stocks and shares: Dot-com bubble (1999–2000) — internet company valuations had no earnings basis; collapsed when investors reassessed
Impact: Misallocation of investment during bubble; severe economic damage when bubble bursts; consumers suffer negative wealth effect (assets less valuable); firms cut investment; banks face bad debts; government faces rising deficit (stimulus needed).
1.3.6
Government Intervention in Markets
Methods of Intervention
| Method | How it works | Best used for | Limitation |
|---|---|---|---|
| Indirect taxes | Raise price of goods with negative externalities | Demerit goods: alcohol, tobacco, fuel | Regressive — poorer households pay higher % income; tax avoidance |
| Subsidies | Lower price/increase supply of goods with positive externalities | Public transport, renewable energy, education | Expensive; may go to wrong recipients; permanent dependency |
| Maximum prices | Price ceiling below equilibrium → prevents price rising above | Housing rent control, food price caps | Creates excess demand/shortages; black markets emerge; supply falls |
| Minimum prices | Price floor above equilibrium → prevents price falling below | Minimum wage, EU farm prices, minimum alcohol unit price | Creates excess supply/surplus; requires government to buy surplus (farm support) |
| Tradeable pollution permits | Cap total pollution; firms buy/sell permits; price creates incentive to reduce emissions | Carbon/CO₂ emissions (EU ETS) | Cap level is political; permits given free initially; difficult globally |
| Extension of property rights | If polluters own the right to pollute and victims can sue, Coase theorem says private bargaining reaches efficient outcome | Noise, pollution, trespass | High transaction costs; works only with small numbers of parties |
| State provision | Government directly provides good/service (NHS, public education) | Public goods; merit goods | Inefficient without profit motive; crowding out; high cost |
| Regulation | Legal rules mandating/prohibiting behaviour (minimum standards, bans) | Building regulations, food safety, financial conduct | Compliance costs; regulatory capture; difficult to enforce |
| Information provision | Correct information failures by publishing data or running campaigns | Nutritional labelling, anti-smoking campaigns | Ignored if not salient; doesn't change price signals |
For any "evaluate a method of government intervention" question, always do: define the problem it addresses → explain the mechanism → analyse who benefits → evaluate one specific limitation → compare briefly to an alternative. End with a qualified judgement: "intervention X is most effective when demand is inelastic/when the information failure is severe/when property rights are well-defined."
Government Failure
Government failure: When government intervention in markets leads to a net welfare loss — the cure is worse than the disease. Not all market failures warrant intervention if the intervention itself creates larger inefficiencies.
Causes of Government Failure
| Cause | Explanation | Example |
|---|---|---|
| Information gaps | Government lacks data to set optimal tax/subsidy/price level | Setting a pollution tax at the wrong level → over/under-corrects |
| Lack of incentives | Public sector lacks profit motive → inefficiency and cost overruns | State-run firms with no competition |
| Unintended consequences | Intervention changes behaviour in unexpected ways | Rent controls → landlords withdraw from rental market → housing shortage worsens |
| Excessive administrative costs | Cost of collecting tax/enforcing regulation exceeds benefit | Small congestion charge raises less than it costs to administer |
| Regulatory capture | Regulated industry influences the regulator → self-serving rules | Financial sector lobbying regulators for looser rules pre-2008 |
| Moral hazard | Intervention creates perverse incentives | Bailouts → banks take more risk in future |
✓ Case for intervention
- Corrects externalities that market ignores
- Provides public goods (defence, law)
- Addresses information failures (NHS)
- Reduces inequality through redistribution
✗ Case against intervention
- Government failure may worsen allocation
- Price signals distorted — misallocation
- Taxes/subsidies have deadweight losses
- Regulatory capture undermines goals
Past Papers
Past Paper Questions & Model Answers
4 marksExplain the difference between a movement along a demand curve and a shift of a demand curve.
Model Answer
A movement along the demand curve (extension or contraction) occurs when the price of the good itself changes — quantity demanded rises or falls along the existing curve. For example, if the price of a bus ticket rises from £2 to £3, quantity demanded falls — this is a contraction of demand.
A shift of the demand curve occurs when any non-price determinant changes — the entire demand curve moves to a new position. For example, a rise in consumer incomes (for a normal good) shifts the demand curve rightward, meaning more is demanded at every price level. Other causes include: changes in price of substitutes or complements, advertising, tastes, or population changes.
Mark scheme: 2 marks for movement along (price change → extension/contraction, example). 2 marks for shift (non-price factor → new curve at all prices, example). Full credit requires distinguishing the cause and effect of each.
5 marksUsing a diagram, explain the effects of a negative externality of production on the allocation of resources.
Model Answer
A negative externality of production occurs when a firm's production imposes external costs on third parties not involved in the transaction — for example, a factory emitting pollution into a river, harming local communities and fish stocks.
The market equilibrium is determined by the intersection of the demand curve (= MPB = MSB) and the firm's supply curve (= MPC). However, because the firm ignores external costs, the Marginal Social Cost (MSC) = MPC + external costs is higher than the MPC at every level of output. The MSC curve lies to the left of the MPC/supply curve.
The socially optimal output Q* is where MSC = MSB (demand). The market produces at Qm where MPC = MPB, which is greater than Q*. The excess output from Q* to Qm represents a welfare loss — the area of the triangle between MSC and MSB from Q* to Qm. The market over-produces relative to the social optimum.
Mark scheme: 1 mark diagram with MPC, MSC, D=MPB=MSB labelled. 1 mark showing Qm and Q*. 1 mark explaining divergence (MPC vs MSC). 1 mark welfare loss area identified. 1 mark clear explanation of over-production.
8 marksExplain the concept of price elasticity of demand and examine its significance for firms when making pricing decisions.
Model Answer
Price elasticity of demand (PED) measures the responsiveness of quantity demanded to a change in price. PED = % change in Qd ÷ % change in Price. PED is always negative (inverse relationship). When |PED| > 1, demand is price elastic; when |PED| < 1, it is price inelastic.
PED is determined by: availability of substitutes (more → more elastic), branding (strong brand → inelastic), percentage of income, addictiveness, and durability.
Significance for firms: A firm with inelastic demand (strong brand, no close substitutes) can raise prices and increase total revenue — the proportionate fall in quantity is smaller than the proportionate rise in price. Apple can raise iPhone prices because of strong brand loyalty and lack of close substitutes (elastic iphones would see revenue fall). Conversely, supermarket own-brand goods face elastic demand — these firms compete on price and must reduce prices to gain market share, increasing revenue through volume.
Firms also use YED to plan across the economic cycle: luxury producers (high YED) plan for volatile sales; staple food producers (low YED) have stable revenues. XED informs merger strategy — high positive XED between two firms suggests they are close competitors.
Mark scheme: Up to 3 marks explain PED (formula, interpretation, determinants). Up to 5 marks analysis of significance (price-setting strategy, TR effect, at least two distinct business applications with examples).
20 marksEvaluate the view that a market for illegal drugs should be legalised and taxed as the most effective way to deal with the negative externalities associated with drug use.
Model Essay Plan
Define: Negative externality — external costs to third parties (crime, NHS burden, addiction strain on families). Market failure — over-consumption beyond socially optimal level. Legalisation with tax = one possible government intervention.
Case for (legalise + tax): Tax internalises the externality — raises price → reduces consumption toward Q*. Government revenue to fund treatment/NHS. Reduces criminal activity (supply chain violence, organised crime eliminated). Quality control — reduces health risks from adulterated products. Portugal drug decriminalisation (2001): drug-related deaths and HIV infections fell significantly; treatment uptake rose.
Case against: Demand for drugs is highly inelastic → legalisation may signal social acceptance → demand rises → externalities increase. Tax revenue could incentivise government to keep drugs legal even if harmful (tobacco). Hard to set the right tax level without perfect information on external costs. Some drugs so harmful that full prohibition may still be optimal.
Alternative 1 — Prohibition: Raises price (supply restricted) → reduces consumption. But black market thrives, criminal externalities large. May be less effective than legalisation + tax.
Alternative 2 — Regulation and treatment provision: Harm reduction approaches — needle exchanges, supervised injection facilities (Switzerland). Addresses externality of disease transmission without signalling acceptance. Limited impact on overall consumption.
Evaluate: Effectiveness depends on PED — if demand is very inelastic, tax raises revenue but doesn't reduce consumption much. Comparison matters — prohibition has failed in many countries. Institutional context (enforcement capacity, healthcare infrastructure) determines relative effectiveness.
Conclude: Legalisation with a high specific tax is likely more effective than prohibition given the failure of prohibition models globally. But the tax must be set high enough to internalise the full external cost, and accompanied by treatment investment — a combined approach addresses both consumption and harm reduction externalities.
Essay Plans
8 × 20-Mark Essay Plans
Essay Plan 1 of 8
Evaluate the view that indirect taxes are the most effective way to correct market failure arising from negative externalities.
Define
Negative externality: external costs imposed on third parties → MSC > MPC → market over-produces. Market failure: misallocation — too much produced at too low a price. Indirect tax: specific or ad valorem per unit.
For taxes
Pigouvian tax = external cost → internalises externality → price rises → consumption falls toward Q*. Revenue raised funds public provision or compensation. Market mechanism maintained (still voluntary). UK fuel duty, tobacco duty are examples.
Limit 1
Information failure: government needs to know exact external cost to set optimal tax. If set wrong, over- or under-corrects. MPC and MSC are both estimated — uncertainty is large.
Limit 2
Regressive impact: taxes on alcohol/fuel take a higher % income from poorer households. Government failure if distributional effects offset efficiency gains.
Alternative 1
Tradeable permits (EU ETS): cap total externality; market allocates permits to highest-value users; price discovery. More flexible but cap-setting still political.
Alternative 2
Regulation: ban or limit polluting activity. Certain reduction but no incentive to reduce below limit; compliance costs; regulatory capture risk.
Conclude
Taxes most effective when: external costs can be quantified, demand is elastic enough to respond, and distributional effects are addressed. Permits better when aggregate emissions cap matters most. Regulation better for severe harms where any level is unacceptable. In practice, combination is most effective.
Pigou (tax theory)Coase (property rights)EU ETS
Essay Plan 2 of 8
Evaluate the view that public goods can only be provided effectively by the government.
Define
Public good: non-rival AND non-excludable. Free-rider problem: rational individuals won't pay → private sector won't provide at all → market failure → state must step in.
For
Non-excludable means no business model: can't charge users → no revenue → no private incentive to supply. National defence, flood protection, street lighting — all require state. Historic evidence: lighthouses were provided privately for centuries (through port levies) but this required creative contract solutions, not free markets.
Evaluate
Technology reduces non-excludability: pay-per-view TV was once a pure public good (broadcast), now excludable via encryption. Some public goods privatised effectively — toll roads, private security firms. The "public good" definition is context-specific.
Limit of state
Government failure: public sector lacks efficiency incentives; cost overruns; provision may be excessive (no price signal). Military spending in some countries may exceed optimal defence provision.
Conclude
For pure public goods (defence, law, flood protection) state provision is necessary — no private model can overcome the free-rider problem. But advancing technology gradually makes exclusion possible for previously non-excludable goods, allowing PPPs or private provision with regulation. The statement is broadly true but less absolute than it seems.
Essay Plan 3 of 8
Evaluate the significance of price elasticity of demand for government decisions on indirect taxation.
Explain PED
PED = %ΔQd ÷ %ΔP. Inelastic: small Q response to P change. Elastic: large Q response. Government taxes shift supply left → consumer pays higher price.
Revenue objective
To maximise tax revenue: tax inelastic goods (tobacco, alcohol, petrol) — price rise → little demand fall → large revenue yield. UK fuel duty raises ~£28bn/year because PED for petrol is low (~-0.3).
Externality objective
To reduce negative externalities: actually want demand to fall. But if PED is inelastic (addictive goods), tax raises price but doesn't much reduce consumption — fails the externality correction goal even if revenue-successful. Contradiction: best revenue base is worst externality correction tool.
Equity concern
Taxes on inelastic goods (food, fuel) are regressive — poor households spend higher % income on these. Government must balance revenue efficiency with distributional equity.
Conclude
PED is highly significant: determines both revenue yield and effectiveness at correcting externality. Key insight: there's a trade-off — inelastic goods generate most revenue but least behavioural change. Government must decide which objective dominates and use complementary policies (information campaigns, spending on alternatives) to complement the tax.
Essay Plan 4 of 8
Evaluate the effectiveness of maximum price controls as a method of government intervention in the housing market.
Define
Maximum price (price ceiling): legal maximum below equilibrium price. Purpose: make housing affordable for low-income households. Market failure: housing is a merit good; income inequality means some cannot access at market price.
Benefits
Reduces rent burden for existing tenants. Allows lower-income households to remain in high-demand areas (London, NYC). Short-run relief from housing cost crisis.
Problems
Creates excess demand (shortage): Qd > Qs at price ceiling. Supply falls — landlords exit the market, convert to short-term lets or sell. Quality deteriorates — landlords cut maintenance. Black markets: key money, side payments. Misallocation: existing tenants stay in properties too large/small for needs rather than move and lose controlled rent.
Evidence
San Francisco rent control (Diamond et al. 2019): reduced rental housing supply by 15% as landlords converted to condos or redeveloped. Berlin rent cap (2020): initially reduced rents but later struck down; rental supply contracted. New York: extensive evidence of shortage and quality deterioration.
Alternative
Supply-side: increase supply through planning reform (deregulation), subsidy to social housing construction. This addresses root cause (insufficient supply) rather than capping symptom (price). Housing benefits (demand-side subsidy) help affordability without restricting supply.
Conclude
Rent controls achieve short-run affordability but long-run worsen housing shortage. Most effective in very short run as emergency measure. Supply-side policies (more building) are more sustainable solutions to a fundamentally supply-constrained market. A combination of targeted housing benefit + planning reform + social housing construction dominates rent controls.
Essay Plan 5 of 8
Evaluate the view that the market mechanism is the most efficient way to allocate resources in an economy.
Define
Price mechanism: signals (price changes convey scarcity), incentives (profit motive drives production), rationing (scarce goods allocated to those who value most). Allocative efficiency: resources used where they generate highest value/consumer surplus.
Case for
Price signals aggregate dispersed information (Hayek 1945 — no central planner can have this knowledge). Profit incentive drives innovation and productivity. Competition eliminates inefficient firms. Consumer sovereignty: people choose what they value. Evidence: market economies vastly outperformed Soviet command economies in productivity and living standards.
Against 1
Market failures: externalities mean prices don't reflect true social costs → misallocation. Public goods under-provided. Information asymmetries distort healthcare, insurance, education markets.
Against 2
Inequality: market allocates to highest willingness to pay → rich get most goods → may be efficient but not equitable. Access to healthcare, education by market mechanism may produce socially unacceptable outcomes.
Against 3
Short-termism: firms maximise short-run profit, under-investing in R&D, infrastructure, and climate protection. Markets fail on intergenerational equity.
Conclude
Markets are most efficient for private goods with well-defined property rights and no significant externalities. But market failures are pervasive in important sectors (healthcare, energy, education, environment), requiring state correction. The question is not market vs. government but optimal mix — markets plus targeted intervention where market failures are significant.
Hayek (1945)Pigou (externalities)Coase (property rights)
Essay Plan 6 of 8
Evaluate the causes and consequences of asymmetric information in the market for healthcare.
Define
Asymmetric information: one party to a transaction has more information than the other. In healthcare: doctors (providers) know more about treatments, diagnoses, and necessity than patients (consumers). Merit good: individuals under-value healthcare benefits.
Causes
Patients lack medical expertise to evaluate necessity or quality of treatment. Complexity and technical specialisation of medicine makes self-assessment impossible. Emotional context (illness/urgency) impairs rational decision-making. Moral hazard with insurance: insured patients over-consume; doctors prescribe more (supplier-induced demand).
Consequences
Under-consumption of preventive healthcare (don't know they need it). Over-consumption of unnecessary procedures (supplier-induced demand). Adverse selection in health insurance (healthy don't buy; sick do → premiums rise → death spiral). Market provides too little healthcare at too high a price without intervention.
Government response
State provision (NHS): ensures access regardless of ability to pay/information. Regulation of professionals (GMC in UK). Compulsory insurance (ACA in US, social insurance in Germany). Mandatory information disclosure. Nudge policies (NHS health checks, cancer screening).
Evaluate
State provision solves access but creates moral hazard (free at point of use → over-use). Limits on supplier-induced demand difficult to police. US mixed system shows private healthcare fails spectacularly on access while cost is highest in world — strongest evidence that healthcare market fails without strong intervention.
Conclude
Asymmetric information in healthcare causes profound market failures on both demand (under-consumption, adverse selection) and supply (supplier-induced demand, quality variability) sides. Justifies substantial intervention — most developed nations use universal coverage models. The market alone produces deeply suboptimal outcomes in healthcare.
Essay Plan 7 of 8
Evaluate the use of subsidies to correct market failure arising from positive externalities in education.
Define
Positive externality of consumption: MSB > MPB. Education creates external benefits: more educated workforce → higher productivity → rising wages for all; more educated citizens → better governance, lower crime. Market under-provides as individuals only consider private benefit.
How subsidy works
Government subsidises education → cost to student falls → demand/consumption rises toward socially optimal Q*. Alternatively subsidise supplier (school/university) → supply shifts right → lower fees → higher uptake. Welfare loss triangle eliminated as market Q moves toward Q*.
Evidence
Returns to education high: Mincer equations show 8-10% private return per extra year of schooling; social returns even higher. OECD countries with strong public education systems show higher social mobility. South Korea's subsidised education expansion → major driver of development.
Limits of subsidy
Cost: universal state education expensive → requires taxation → may cause government failure elsewhere. Moral hazard: free education may reduce incentive to complete/apply effort (UK tuition fees debate). Hard to target subsidy efficiently — benefits middle/upper-income families (university) more than poorest (who don't attend).
Alternatives
State provision (guaranteed access, quality control). Regulation (compulsory schooling age 5–16 in UK). Information campaigns (raise awareness of education returns to under-represented groups).
Conclude
Subsidies and state provision for education are strongly justified by positive externalities — returns clearly exceed private value. Primary/secondary education: near-universal state provision justified (high external returns, severe inequality without it). Higher education: subsidy partially justified but tuition fees can internalise some private return while bursaries maintain access. Full state funding more appropriate for children; mixed model for higher education.
Essay Plan 8 of 8
Evaluate the view that government failure means that government intervention to correct market failure will always make things worse.
Define
Government failure: intervention results in net welfare loss — allocation worse than without intervention. Market failure: price mechanism fails to achieve allocative efficiency (externalities, public goods, information gaps).
Causes of gov failure
Information gaps (don't know optimal tax level). Unintended consequences (rent control → fewer rentals). Regulatory capture (industry lobbying weakens regulation). Short-term political cycle (vote-winning policies over efficient ones). Moral hazard (bailouts → reckless banking).
Examples of failure
CAP: agricultural subsidies create butter mountains, distort global markets, benefit large landowners over small farmers. US ethanol subsidy: raised food prices globally, increased some emissions. Rent controls in NYC/San Francisco → housing shortages. Financial deregulation pre-2008 → moral hazard → financial crisis.
Counter-argument
Many interventions successful: NHS provides healthcare with better outcomes and lower cost than US private system. Tobacco taxation has reduced smoking significantly. Clean Air Acts improved air quality dramatically. Government failure is not inevitable — it depends on quality of information, institutional design, and political independence.
Evaluate
The claim is too strong — it commits the "nirvana fallacy" of comparing real government failure with idealised markets. The real comparison is between imperfect markets and imperfect governments. In some cases (large negative externalities, public goods) intervention clearly improves welfare despite imperfection. In other cases (rent controls, complex regulation) failure dominates.
Conclude
Government failure is a genuine risk but not inevitable. Well-designed, targeted interventions with independent regulatory oversight can and do improve market outcomes. The statement "always worse" is empirically false — healthcare, clean air, financial stability are all improved by thoughtful intervention. The correct lesson is not "don't intervene" but "intervene carefully and evaluate outcomes rigorously."