[4] Gains from trade are commonly described as resulting from: Market incentives, such as reflected in prices of outputs and inputs, are theorized to attract factors of production, including labor, into activities according to comparative advantage, that is, for which they each have a low opportunity cost.
The factor owners then use their increased income from such specialization to buy more-valued goods of which they would otherwise be high-cost producers, hence their gains from trade.
[9] David Ricardo in 1817 first clearly stated and proved the principle of comparative advantage,[10] termed a "fundamental analytical explanation" for the source of gains from trade.
[11] But from publication of Adam Smith's The Wealth of Nations in 1776, it was widely argued, that, with competition and absent market distortions, such gains are positive in moving toward free trade and away from autarky or prohibitively high import tariffs.
[12] For the analytically tractable general case of Arrow-Debreu goods, formal proofs came in 1972 for determining the condition of no losers in moving from autarky toward free trade.