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Theorem

Lerner Symmetry Theorem

Game Theory

The Lerner symmetry theorem, in international trade theory, states that an ad valorem tariff imposed on imports has, under the theorem's general equilibrium assumptions, the same economic effect as an equivalent tax placed on exports. The result relies on a model of an economy with perfect competition, no transaction costs, balanced trade, and fully flexible prices and exchange rates, and it is named for the economist Abba Lerner.

Facts
Statement
an ad valorem import tariff will have the same effects as an equivalent export tax 1
Proof Year
1936 1
Classification
Statement Form
Characterization Theorem 1
Connections

Has Statement Form

Entity-backed identity for the statement-form enum value this theorem already carries, resolved to a mathematics concept by an explicit value-to-entity map (phase 3 bucket conversion, docs\design_entity_backed_browse_buckets_20260928.md). The statement-form fact itself stays on the theorem unchanged.

Sources
1. Lerner symmetry theorem - Wikipedia
  • Introduction
    an ad valorem import tariff will have the same effects as an equivalent export tax
  • History section
    The theorem was developed by economist Abba P. Lerner in 1936.
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