The Lerner symmetry theorem is a result used in trade

Trade

Trade is the transfer of ownership of goods and services from one person or entity to another. Trade is sometimes loosely called commerce or financial transaction or barter. A network that allows trade is called a market. The original form of trade was barter, the direct exchange of goods and...

 theory, which states that, based on an assumption of a zero balance of trade

Balance of trade

The balance of trade is the difference between the monetary value of exports and imports of output in an economy over a certain period. It is the relationship between a nation's imports and exports...

 (that is, the value of exported goods equals the value of imported goods for a given country), an ad valorem import tariff (a percentage of value or an amount per unit) will have the same effects as an export tax. The theorem is based on the observation that the effect on relative prices is the same regardless of which policy (ad valorem tariffs or export taxes) is applied.

The theorem was developed by economist Abba P. Lerner

Abba P. Lerner

Abba Ptachya Lerner was an American economist.Lerner was born on October 28, 1903 in Bessarabia . He grew up in a Jewish family, which emigrated to Great Britain when Lerner was three years old. Lerner grew up in the London East End. From the age of sixteen he worked as a machinist, a teacher in...

.

Further reading

• A. P. Lerner, "The Symmetry Between Import and Export Taxes", Economica, New Series, Vol. 3, No. 11 (1936), pp. 306-313.