Difference in value over a period of time between a nation's imports and exports of goods and services.
The balance of trade is part of a larger economic unit, the balance of payments , which includes all economic transactions between residents of one country and those of other countries. If a nation's exports exceed its imports, the nation has a favourable balance of trade, or a trade surplus. If imports exceed exports, an unfavourable balance of trade, or a trade deficit, exists. Under mercantilism a favourable balance of trade was an absolute necessity, but in classical economics it was more important for a nation to utilize its economic resources fully than to build a trade surplus. The idea of the undesirability of trade deficits persisted, however, and arguments against deficits are often advanced by advocates of protectionism .