A scale of charges. In economics a tariff was originally a schedule of taxes on imports; it now refers to the actual import duties. An ad valorem tariff is set as a percentage of the price of the goods imported. A specific tariff is set in money terms per physical unit of the good imported, and does not depend on its price. A non-discriminatory tariff taxes imports from all countries equally; tariff preferences mean that similar imports from different countries are taxed at different rates. See also optimum tariff; prohibitive tariff; revenue tariff; two-part tariff.