Tariff
A tariff is a tax on imports or exports between sovereign states. It is a form of regulation of foreign trade. It is a policy that taxes foreign products to encourage or protect domestic industry. It helps limit trade deficits. The tariff is historically used to protect infant industries and to allow import substitution industrialization.
Customs duties in the United States
Customs duty rates may be expressed as a percentage of value or dollars and cents per unit. Rates based on value vary from zero to 20% in the 2011 schedule. Rates may be based on relevant units for the particular type of goods (per ton, per kilogram, per square meter, etc.). Some duties are based in part on value and in part on quantity. The United States applies a Customs tariff that is among the lowest in the world: 3% on average.