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.
Tariff
The overall change in welfare = Change in Consumer Surplus + Change in Producer Surplus + Change in Government Revenue = (-A-B-C-D) + A + C = -B-D. The final state after imposition of the tariff is indicated in the second diagram, with overall welfare reduced by the areas labeled "societal losses", which correspond to areas B and D in the first diagram. The losses to domestic consumers are greater than the combined benefits to domestic producers and government.