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Tax incidence

Measure of the economic effect of a tax

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Through Economics, Tax and Price elasticity of demand

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 is the finding that the tax burden does not depend on where the revenue is collected, but on the price elasticity of demand and price elasticity of supply.

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 nominally paid half by the employee and half by the employer. However, economists generally find that workers bear most of the burden of the tax, because the employer passes it on in the form of lower wages. The tax incidence is thus said to fall mainly on the employee.

Tax incidence in competitive markets

In competitive markets, firms supply a quantity of the product such that 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 (p0+kt),k∈[0,1].

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 (p0−(1−k)t),k∈[0,1]) that producers will receive at given quantity. In Figure 1, 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.

It also does not matter whether the tax is levied as a percentage of the price (say ad valorem tax) or as a fixed sum per unit (say specific tax). Both are graphically expressed as a shift of the demand curve to the left. While the demand curve moved by specific tax is parallel to the initial, the demand curve shifted by ad valorem tax is touching the initial, when the price is zero and deviating from it when the price is growing. However, in the market equilibrium both curves cross.

Income taxes are taxes on the supply of labor (if the income is wages) or capital (if the income is dividends, for example). Corporate income tax incidence is difficult to evaluate because although the direct burden is on corporate shareholders, the tax tends to move capital to be supplied more to non-corporate uses such as housing or partnerships, reducing the return to capital generally, and it moves capital abroad, reducing wages. Thus, in the long-run, once the quantity of capital has adjusted, the incidence is likely on non-corporate capital as much as corporate capital, and much of it may be on labor. Economists' estimates of the incidence vary widely.

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