In economics, tax incidence or tax burden is the effect of a particular tax on the distribution of economic welfare. Economists distinguish between the entities who ultimately bear the tax burden and those on whom the tax is initially imposed. The tax burden measures the true economic effect of the tax, measured by the difference between real incomes or utilities before and after imposing the tax, and taking into account how the tax causes prices to change. For example, if a 10% tax is imposed on sellers of butter, but the market price rises 8% as a result, most of the tax burden is on buyers, not sellers. The concept of tax incidence was initially brought to economists' attention by the French Physiocrats, in particular François Quesnay, who argued that the incidence of all taxation falls ultimately on landowners and is at the expense of land rent. Tax incidence is said to "fall" upon the group that ultimately bears the burden of, or ultimately suffers a loss from, the tax. The key concept of tax incidence (as opposed to the magnitude of the tax) is that the tax incidence or tax burden does not depend on where the revenue is collected, but on the price elasticity of demand and price elasticity of supply. As a general policy matter, the tax incidence should not violate the principles of a desirable tax system, especially fairness and transparency. The concept of tax incidence is used in political science and sociology to analyze the level of resources extracted from each income social stratum in order to describe how the tax burden is distributed among social classes. That allows one to derive some inferences about the progressive nature of the tax system, according to principles of vertical equity.
The theory of tax incidence has a number of practical results. For example, United States Social Security payroll taxes are paid half by the employee and half by the employer. However, some economists think that the worker bears almost the entire burden of the tax because the employer passes the tax on in the form of lower wages. The tax incidence is thus said to fall on the employee. However, it could equally well be argued that in some cases the incidence of the tax falls on the employer. This is because both the price elasticity of demand and price elasticity of supply effect upon whom the incidence of the tax falls. Price controls such as the minimum wage which sets a price floor and market distortions such as subsidies or welfare payments also complicate the analysis.
Tax incidence in competitive markets
In competitive markets firms supply quantity of the product equals to the level at which the price of the good equals marginal cost (supply curve and marginal cost curve are indifferent). If an excise tax (a tax on the goods being sold) is imposed on producers of the particular good or service, the supply curve shifts to the left because of the increase of marginal cost. The tax size predicts the new level of quantity supplied, which is reduced in comparison to the initial level. In Figure 1 – a demand curve is added into this instance of competitive market. The demand curve and shifted supply curve create a new equilibrium, which is burdened by the tax. The new equilibrium (with higher price and lower quantity than initial equilibrium) represents the price that consumers will pay for a given quantity of good extended by the part of the tax
The point on the initial supply curve with respect to quantity of the good after taxation represents the price (from which the part of the tax is subtracted that producers will receive at given quantity. In this case, the tax burden is borne equally by the producers and consumers. For example, if the initial price of the good is $2, and the tax levied on the production is $.40, consumers will be able to buy the good for $2.20, while producers will receive $1.80.
Consider the case when the tax is levied on consumers. Unlike when tax is imposed on producers, the demand curve shifts to the left to create new equilibrium with initial supply (marginal cost) curve. The new equilibrium (at a lower price and lower quantity) represents the price that producers will receive after taxation and the point on the initial demand curve with respect to quantity of the good after taxation represents the price that consumers will pay due to the tax. Thus, it does not matter whether the tax is levied on consumers or producers.