: Ricardo posits that the exchange value of most commodities is determined by the total quantity of labor required for their production.
David Ricardo (1772 – 1823) was a prominent classical economist who gave a systematized form to a rising discipline of 'economics' economicsociology.org
: Ricardo's most famous contribution. It argues that international trade is mutually beneficial if countries specialize in goods where they have the lowest relative opportunity cost, even if one country is more efficient at producing everything.
On the Principles of Political Economy and Taxation - Econlib