Elasticity determines economic tax incidence

The side with fewer alternatives changes quantity less and bears more burden.

A tax creates a wedge between buyer and seller prices. If demand is less elastic than supply, buyers bear more through a larger price increase. If supply is less elastic, sellers bear more through a larger reduction in the price they receive. The side legally required to send money to government does not determine the economic burden.

Tax incidence asks who experiences the change relative to the original equilibrium price. If the old price is $10, buyers now pay $13, and sellers keep $9, a $4 tax is split: buyers bear $3 per unit and sellers bear $1. Buyers therefore bear three-fourths of the per-unit burden. The full wedge is buyer price minus seller price, not buyer price minus the tax.

Elasticity explains the split through avoidance. The more elastic side can reduce its market participation more readily and therefore escapes more of the burden. The less elastic side has fewer alternatives and changes quantity less, so more of the tax is reflected in its price. This is a comparative statement: both elasticities matter.

Statutory incidence identifies who remits the tax to government. Economic incidence identifies whose real price changes. Changing the remittance rule from sellers to buyers does not change the basic equilibrium if enforcement and transaction conditions are otherwise identical. Market adjustment recreates the same wedge.

A vertical supply curve

The number of beachfront parcels is fixed, so supply is perfectly inelastic. A recurring per-parcel tax cannot reduce the number of parcels. Demand determines what buyers will pay, and sellers receive the buyer price minus the tax. In the basic model, landowners bear the tax through a lower net price even if buyers write the check.

Do not infer burden from a curve’s label alone. “Demand is inelastic” does not prove buyers bear more unless supply is more elastic. If both sides are very inelastic, compare their relative responsiveness or use the price changes shown. Incidence is about the two curves together.

Tax burden and deadweight loss are different. Burden is the loss of buyer or seller surplus transferred partly to government. Deadweight loss comes from trades that no longer occur. A perfectly inelastic side can bear the entire burden while quantity remains unchanged and the standard deadweight loss is zero.

If exact elasticities are supplied, compare their absolute magnitudes. Demand with |E_d|=0.4 is less elastic than supply with E_s=1.2, so buyers bear more. Do not compare the signed demand value -0.4 directly with +1.2 on the number line. Incidence depends on responsiveness magnitudes.

The post-tax quantity is shared by both sides, so incidence changes prices, not separate buyer and seller quantities.