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Indirect taxes and subsidies are the most common ways governments intervene in individual markets, and they are a direct application of everything studied so far: supply shifts, equilibrium adjustment, elasticity and surplus. An indirect tax raises a producer's costs and shifts supply up and to the left; a subsidy lowers costs and shifts supply down and to the right. The interesting questions are who really pays a tax (the "incidence"), who really gains from a subsidy, how big the resulting deadweight loss is, and whether such intervention is justified. The answers turn on elasticity — but this lesson references price elasticity of demand rather than re-teaching it (the elasticity lessons cover that in full); the focus here is on the diagrams, the incidence split, the welfare effects, and evaluation.
This lesson maps primarily to AQA 7136 section 4.1.3 — how markets work (the effect of indirect taxes and subsidies on the market), and links forward to section 4.1.5 — market failure and government intervention (taxes and subsidies as tools to correct externalities) and to the macroeconomic use of indirect taxes and subsidies in fiscal policy (Paper 2). It is examined mainly in Paper 1 (Markets and market failure) through diagram and calculation data response and 25-mark evaluation. All four assessment objectives apply: AO1 for the types of tax and the mechanics, AO2 for applying the analysis to named UK markets, AO3 for chains linking the supply shift to price, quantity, incidence and welfare, and AO4 for evaluating effectiveness, distribution and the risk of government failure.
Key Definition: A direct tax is levied on income or wealth and paid directly to the government by the person or firm on whom it falls. An indirect tax is levied on spending and is collected by the seller, who passes it to the government — so the burden may be shifted onto someone else.
| Type | Levied on | UK examples |
|---|---|---|
| Direct | Income or wealth | Income tax, corporation tax, capital gains tax, inheritance tax |
| Indirect | Spending / expenditure | VAT, excise duties on tobacco, alcohol and fuel, the Soft Drinks Industry Levy, air passenger duty |
Because indirect taxes are levied on transactions, they act on the supply side of a market — and crucially, who legally pays the tax (the seller) need not be who economically bears it, which is the central theme of tax incidence below.
There are two forms of indirect tax, and they shift the supply curve differently.
Key Definition: A specific (unit) tax is a fixed amount per unit sold, regardless of price. An ad valorem tax is a percentage of the selling price.
A specific tax shifts supply up by a constant vertical amount at every quantity, so the new supply curve is parallel to the old one. An ad valorem tax is a percentage, so the absolute gap widens as price rises, and the new supply curve pivots away (diverges) from the old one.
UK illustrations: excise duties on tobacco, alcohol and fuel are specific taxes (a set amount per unit), as is the Soft Drinks Industry Levy (a fixed pence-per-litre charge banded by sugar content); VAT at the standard rate is the UK's main ad valorem tax (a percentage of price).
Exam Tip: Draw a specific tax as a parallel upward shift and an ad valorem tax as a diverging (pivoting) shift. Examiners award easy marks for the correct geometry — and penalise a parallel shift labelled "VAT".
When a specific tax of a set amount per unit is imposed, the supply curve shifts up by the tax. The new equilibrium has a higher price paid by consumers (P_c) and a lower quantity (Q₁). The price producers keep (P_p) is the consumer price minus the tax, so the vertical gap between P_c and P_p is exactly the tax per unit.
The shaded bands split the tax: the band from the original price P_e up to the consumer price P_c is the consumer's share of the burden; the band from P_e down to the producer price P_p is the producer's share. The two bands together, multiplied by the new quantity Q₁, give the government's tax revenue:
Tax revenue=(Pc−Pp)×Q1
Key Definition: Tax incidence is the way the burden of a tax is actually divided between consumers (through higher prices) and producers (through lower net revenue), regardless of who legally hands the tax to the government.
The split depends on the relative elasticities of demand and supply. (The detailed theory and calculation of price elasticity of demand belong to the elasticity lessons; here we simply apply the elasticity result.) The intuition is that the burden falls more heavily on whichever side of the market is less able to escape — that is, the more inelastic side.
| Relative elasticity | Burden falls mainly on | Consumer price rises by | Revenue |
|---|---|---|---|
| Demand inelastic, supply elastic | Consumers | A lot | High |
| Demand elastic, supply inelastic | Producers | A little | Lower |
| Both inelastic | Shared, leaning to consumers | Moderate | High |
When demand is inelastic (consumers cannot easily cut back) and supply is elastic, producers pass most of the tax forward as a higher price, so consumers bear most of the burden. This is exactly why a tax on a good with inelastic, addictive demand — such as tobacco — falls largely on the consumer and raises substantial revenue: smokers reduce consumption only modestly, so the price rises by close to the full tax and the government collects a large, fairly stable revenue. When demand is elastic (consumers readily switch away) and supply is inelastic, producers cannot raise the price much without losing sales, so they absorb most of the tax through a lower net price.
It helps to see why this works by reasoning from the side of the market that can most easily escape. A tax is, in effect, a wedge driven between the price the buyer pays and the price the seller keeps. Whoever can most readily change their quantity in response — the more elastic side — can avoid the tax, because they will simply trade less rather than accept a worse price; the burden is then shoved onto the side that cannot easily change quantity, the more inelastic side. So the rule is symmetric and intuitive: the relatively inelastic side bears the larger share of the burden, because it has the fewest alternatives and is therefore least able to walk away. The polar cases make this vivid. If demand is perfectly inelastic (a vertical demand curve — consumers will buy the same quantity at any price), consumers bear the entire tax: the price rises by the full amount of the tax and quantity does not fall at all. If demand is perfectly elastic (a horizontal demand curve — consumers will desert the good entirely at any price above the going rate), producers bear the entire tax, since they cannot raise the price by a penny without losing every sale. Real markets sit between these extremes, but reasoning from them tells you instantly which way the burden will lean.
Exam Tip: In any incidence question, draw both P_c and P_p and shade the two burden bands. State which is larger and justify it by elasticity: "because demand is inelastic and supply elastic, the consumer burden band is larger". That sentence is the AO3 heart of the answer.
Suppose a good originally sells at an equilibrium price of £2.00 with 1,000 units traded. The government imposes a specific tax of £0.50 per unit. Because demand is fairly inelastic, the new consumer price rises to £2.40 and the quantity falls only modestly to 900 units; the price producers keep is the consumer price minus the tax, £2.40 − £0.50 = £1.90. The burden then splits as follows:
So consumers bear £0.40 of the £0.50 tax (80%) and producers bear £0.10 (20%) — consistent with demand being more inelastic than supply, so consumers cannot easily escape the tax. The government's revenue is the tax per unit times the new quantity:
Tax revenue=£0.50×900=£450
Notice that revenue is calculated on the new, lower quantity (900), not the original 1,000 — a common slip. Notice too that because demand was inelastic, the quantity fell only 10%, so the tax raised substantial revenue with a small deadweight loss: exactly the property that makes such goods attractive to tax.
Using the surplus tools from the previous lesson, a tax reduces total welfare:
The size of the deadweight loss depends on elasticity: the more elastic demand and/or supply, the larger the fall in quantity and the bigger the welfare loss. This is the key efficiency argument behind tax design — and it explains the apparent paradox that governments often tax goods with inelastic demand (tobacco, fuel, alcohol). With inelastic demand the quantity barely falls, so the deadweight loss is small while the revenue is large. (Note the important exception: where a good generates a negative externality, a tax that cuts output towards the social optimum can improve welfare rather than reduce it — explored under market failure.)
This produces a genuine tension at the heart of tax design that is worth stating explicitly, because it generates strong evaluation. A tax raises the most revenue, with the smallest efficiency cost, precisely when demand is inelastic — but inelastic demand is also exactly the condition under which the tax does least to change behaviour. So a duty on a demerit good faces a dilemma: the very property (inelasticity) that makes it an efficient revenue raiser makes it a weak behaviour-change tool, and vice versa. A government that wants chiefly to raise money will therefore favour taxing goods with inelastic demand and few substitutes (which is why fuel, tobacco and alcohol are perennial revenue targets); a government that wants chiefly to cut consumption of a harmful good may be frustrated that the same inelasticity blunts the behavioural effect. Seeing that revenue and behaviour-change pull in opposite directions — and that the "right" tax depends on which objective dominates — is one of the most reliable ways to push an answer on indirect taxes into the top band.
It is also worth distinguishing the deadweight loss from the distributional effect of the tax. The deadweight loss is a pure efficiency cost: welfare destroyed because some mutually beneficial trades no longer happen. But a tax also redistributes — from consumers and producers to the government — and that transfer is welfare-neutral in aggregate even though it makes the taxed parties worse off and (potentially) funds valuable public spending. Keeping the efficiency cost (the triangle) separate from the transfer (the revenue rectangle) is essential: a common error is to treat the entire fall in consumer-plus-producer surplus as a "loss to society", when in fact most of it has merely changed hands.
Key Definition: A subsidy is a payment by the government to producers that lowers their costs of production, encouraging output and lowering the price to consumers.
A subsidy shifts the supply curve down and to the right by the amount of the subsidy. The new equilibrium has a lower price for consumers (P_c) and a higher quantity (Q₁). The price producers receive, P_p, is higher than the consumer price by the subsidy per unit (the consumer price plus the per-unit subsidy). The cost to the government is:
Government spending=(Pp−Pc)×Q1
The welfare effects mirror a tax in reverse: consumer surplus rises (lower price, more bought), producer surplus rises (higher net price, more sold), but there is a cost to taxpayers funding the subsidy, and a deadweight loss if the subsidy pushes output beyond the socially efficient level (so that resources produce units whose cost exceeds their value). Just as with a tax, who benefits more depends on elasticity: with inelastic demand the price falls little, so producers capture most of the benefit; with elastic demand the price falls a lot, so consumers gain more.
A standard UK example is government support for renewable energy through schemes that effectively subsidised low-carbon electricity, shifting its supply to the right, lowering costs and encouraging investment in wind and solar capacity.
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