Excise Tax vs Tax Incidence
Excise Tax and Tax Incidence are two Supply & Demand concepts in AP Economics that students often mix up. An excise tax is a tax levied on the production or sale of a specific good or service. Tax incidence refers to the distribution of the tax burden between buyers and sellers. Here is how they compare side by side.
Excise taxes are typically applied to goods with negative externalities, like cigarettes or alcohol, to discourage consumption and raise revenue. They shift the supply curve upward by the amount of the tax.
The incidence of a tax depends on the relative elasticities of supply and demand. If demand is more inelastic than supply, consumers bear a larger share of the tax burden. If supply is more inelastic than demand, producers bear a larger share.
Excise Tax vs Tax Incidence: The Policy and the Question of Who Pays
| Excise Tax | Tax Incidence | |
|---|---|---|
| What it is | A tax of a set amount on each unit of a specific good | The division of the tax burden between buyers and sellers |
| What decides it | The legislature, which picks the amount and the legal payer | The relative elasticities of demand and supply |
| Units it is measured in | Dollars per unit, or a percentage of the price | A share of the tax, or the dollars borne by each side |
| How it appears on the diagram | A vertical wedge driven between the two curves | Where the original equilibrium price cuts that wedge |
| Effect of rewriting which side remits the money | The legal payer changes | Nothing changes; the split comes out the same |
| What it directly determines | The size of the wedge and the drop in quantity | How much of the wedge each side actually absorbs |
The law names a payer and the market picks who pays
An excise tax is the instrument. Incidence is the outcome. A legislature can write the law so that sellers hand over the money, and that choice still does not decide who ends up poorer. Work an illustrative market where quantity demanded equals 120 minus 2P and quantity supplied equals 4P. Before any tax the two cross at a price of 20 with 80 units traded. Now add an excise tax of 6 per unit collected from sellers. The price buyers pay rises to 24, the amount sellers keep falls to 18, and quantity drops to 72 units. Check both sides at those prices: buyers demand 120 minus 48, which is 72, and sellers supply 4 times 18, which is 72. So the tax lifted the buyers' price by 4 and cut the sellers' price by 2. Buyers absorb two thirds of the 6 and sellers absorb one third, even though sellers are the ones remitting it. Revenue is 6 times 72, or 432. Rewriting the law to collect the same 6 from buyers produces the identical split, the identical quantity and the identical revenue. Practise splitting a tax at /calculate/tax-incidence.
Elasticity decides the split, and the side that cannot walk away pays more
The rule is short. Whichever side of the market can more easily change what it does bears less of the tax. In the market above, quantity supplied responds twice as strongly to a price change as quantity demanded does, so sellers escape with a third of the burden while buyers carry two thirds. Reverse the responsiveness and the shares reverse with it. The two limiting cases are worth memorizing, because questions lean on them. With perfectly inelastic demand, buyers purchase the same quantity at any price, the whole tax lands on them, the price they pay rises by the full amount and quantity does not fall at all. With perfectly elastic demand, sellers absorb everything instead. The same logic runs on the supply side. Quantity is what links incidence to efficiency. A tax that barely changes quantity raises revenue with little waste, because few worthwhile trades are prevented. A tax on a good where both curves are elastic cuts quantity sharply, so it collects less and destroys more value per dollar raised. Goods with few substitutes are therefore common targets. Measurement is covered at /micro/elasticity.
Frequently asked questions
Who really pays an excise tax?
The side of the market with the less elastic curve pays the larger share of an excise tax, whichever side the law requires to send the money in. Buyers who have few substitutes and keep purchasing as the price rises absorb most of it. Sellers who can shift their resources into other products easily absorb very little.
Does it matter whether a tax is placed on buyers or sellers?
No, the burden split, the quantity traded and the revenue collected all come out the same either way. Placing it on sellers shifts supply up by the tax and placing it on buyers shifts demand down by the tax, and both open the same gap between what buyers pay and what sellers keep. Only the legal duty to remit the money differs.
How do you find the consumer's share of an excise tax?
Divide the rise in the price buyers pay by the size of the tax per unit. If a tax of 5 per unit lifts the buyers' price from 12 to 15, that rise of 3 is three fifths of the tax, so consumers bear 60 percent of it. Sellers bear whatever remains, here two fifths, or 40 percent.
Live Supply and Demand graph. Drag the curves, or open the full version.
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