SUMMARY

1. Excise taxes—taxes on the purchase or sale of a good—raise the price paid by consumers and reduce the price received by producers, driving a wedge between the two. The incidence of the tax—how the burden of the tax is divided between consumers and producers—does not depend on who officially pays the tax.

2. The incidence of an excise tax depends on the price elasticities of supply and demand. If the price elasticity of demand is higher than the price elasticity of supply, the tax falls mainly on producers; if the price elasticity of supply is higher than the price elasticity of demand, the tax falls mainly on consumers.

3. The tax revenue generated by a tax depends on the tax rate and on the number of taxed units transacted. Excise taxes cause inefficiency in the form of deadweight loss because they discourage some mutually beneficial transactions. Taxes also impose administrative costs: resources used to collect the tax, to pay it (over and above the amount of the tax), and to evade it.

4. An excise tax generates revenue for the government but lowers total surplus. The loss in total surplus exceeds the tax revenue, resulting in a deadweight loss to society. This deadweight loss is represented by a triangle, the area of which equals the value of the transactions discouraged by the tax. The greater the elasticity of demand or supply, or both, the larger the deadweight loss from a tax. If either demand or supply is perfectly inelastic, there is no deadweight loss from a tax.

5. An efficient tax minimizes both the sum of the deadweight loss due to distorted incentives and the administrative costs of the tax. However, tax fairness, or tax equity, is also a goal of tax policy.

6. There are two major principles of tax fairness, the benefits principle and the ability-to-pay principle. The most efficient tax, a lump-sum tax, does not distort incentives but performs badly in terms of fairness. The fairest taxes in terms of the ability-to-pay principle, however, distort incentives the most and perform badly on efficiency grounds. So in a well-designed tax system, there is a trade-off between equity and efficiency.

7. Every tax consists of a tax base, which defines what is taxed, and a tax structure, which specifies how the tax depends on the tax base. Different tax bases give rise to different taxes—the income tax, payroll tax, sales tax, profits tax, property tax, and wealth tax. A proportional tax is the same percentage of the tax base for all taxpayers.

8. A tax is progressive if higher-income people pay a higher percentage of their income in taxes than lower-income people and regressive if they pay a lower percentage. Progressive taxes are often justified by the ability-to-pay principle. However, a highly progressive tax system significantly distorts incentives because it leads to a high marginal tax rate, the percentage of an increase in income that is taxed away, on high earners. The U.S. tax system is progressive overall, although it contains a mixture of progressive and regressive taxes.