Tax Incidence and Elasticity

A per-unit tax creates a gap between the price buyers pay and the amount sellers keep. This gap is the tax wedge:

where $P_b$ is the buyer price, $P_s$ the seller receipt, and $t$ the tax per unit. The market quantity must satisfy demand at $P_b$ and supply at $P_s$.

Legal payment and economic burden differ

Tax law may require a shop, platform, or buyer to send money to government. This is statutory incidence. Economic incidence asks whose real purchasing power falls after prices and quantities adjust.

If a delivery platform must remit an 8-unit tax, it may raise customer fees, lower courier payments, accept a smaller margin, or combine these responses. The legal payer does not mechanically determine the final burden.

The less elastic side bears more

Elasticity measures the ability to change quantity when price changes. A side with few alternatives cannot easily leave the market, so more of the wedge appears on that side.

For small changes near an equilibrium, a useful approximation is

The opposite side's elasticity appears in each numerator. If demand is very inelastic and supply elastic, buyers bear most of the tax. If sellers have fixed short-run capacity while buyers can switch easily, sellers bear more.

Reading the supply-demand diagram

A tax can be drawn by shifting one curve vertically by the tax amount or by placing a wedge between demand and supply. The new traded quantity is lower because some trades no longer cover buyer value, seller cost, and tax together.

At the new quantity, read the buyer price from demand and the seller price from supply. Their difference must equal the tax. Multiplying the tax by quantity gives government revenue.

Context matters

Elasticity changes with time, market definition, and available alternatives. Commuters may bear more of a transport tax immediately but adjust routes or housing over several years. A tax on one narrow product may be easier to avoid than a tax on a broad category.

Incidence can also pass through wages, rents, quality, or waiting time. A complete study states the market, period, population, and adjustment channels rather than claiming that one side always pays.

Work through an incidence calculation

Suppose a delivery order is taxed 8, demand elasticity is 0.5, and supply elasticity is 1.5. The approximate buyer share is

Buyers bear about 6 per order and sellers about 2. If the original price was 30, buyers now pay about 36 while sellers receive about 28. The difference, $36-28=8$, confirms the tax wedge.

Notice the direction of the formula. The buyer share contains supply elasticity. Highly elastic suppliers can leave the market easily, so buyers must absorb more of the wedge. The side that is trapped more tightly bears more burden.

Time changes incidence

Immediately after a fuel or transport tax, commuters may have fixed homes, jobs, and vehicles, making demand inelastic. Over several years they can move, change routes, or replace vehicles. Demand becomes more elastic, and the burden can move toward suppliers or other linked markets.

Incidence can also appear through dimensions other than posted price. Platforms may change service fees, worker bonuses, product quality, waiting time, or contract terms. A study that observes only one listed price may miss part of the adjustment.

Use the formula as a model, not a slogan

The elasticity-share formula is a local approximation. Large taxes can move the market into regions with different elasticities. Legal rules, minimum prices, bargaining power, and evasion can also matter. State the market, time period, and adjustment channels before applying a numerical result.