Time: Mid-18th century, proposed by Adam Smith.

Economic Development: Early Industrial Revolution, Production technology began to develop rapidly, International trade began to receive attention.

Improvement: Relative to mercantilism, The theory of absolute advantage proposes that trade can be based on differences in production efficiency, thereby achieving mutual benefit.

Improvement: The theory of comparative advantage expands the theory of absolute advantage, Point out that even if a country does not have an absolute advantage in the production of all goods, Trade benefits can also be obtained by focusing on the production of goods with greater comparative advantage

Economic development: The industrial revolution further developed and the scale of international trade expanded.

Time: Early 19th century, proposed by David Ricardo.

Time: Early 19th century, the same period as the theory of comparative advantage.

Economic Development: Same as above

Improvement: The Ricardian model further refines the theory of comparative advantage, The distributional effects of trade are explained through mathematical models.

Time: Mid-to-late 19th century, proposed by John Stuart Mill.

Economic development: With the establishment of the gold standard system, the role of currency in international trade began to be taken seriously.

Improvement: The model not only considers exchange rate factors, Production costs and transportation costs are also included, Make the theory closer to the actual conditions of international trade.

Time: 1930s, proposed by Heckscher and Ohlin.

Economic Development: During the Great Depression, international trade policy received attention.

Improvement: Explain the pattern of international trade from the perspective of production factor endowment, The Ricardian model is supplemented to explain trade between similar countries.

Time: 1940s, Contributed by Paul Samuelson and Wolfgang Stolper.

Economic development: discussions of international trade policy and protectionism after World War II.

Improvement: Explains the impact of trade policy on income distribution among different factors of production, Especially under protectionist policies.

Time: 1930s, Proposed by Polish economist Tadeusz Rybzinski.

Economic development: Same as H-O theory.

Improvement: Based on the H-O model, Discussed the impact of trade on resource allocation, Especially the impact on the prices of production factors.

Time: 1970s, Proposed by Paul Krugman et al.

Economic development: increased trade between similar countries in international trade, Especially intra-industry trade.

Improvement: explained the existence of intra-industry trade between similar countries, Economies of scale and product differentiation are emphasized.

Time: 1960s, proposed by Bertil Olin.

Economic development: emphasis on product differentiation and consumer preferences in international trade.

Improvement: Explains the impact of product differentiation and consumer preferences on trade patterns in international trade.

Time: 1970s, the same period as intra-industry trade theory.

Economic development: globalization and deepening of international trade, The role of economies of scale in international trade is increasingly evident.

Improvement: Emphasized the role of economies of scale in international trade, Explains how trade facilitates the realization of economies of scale.

Time: 1950s, proposed by Gruber and Vernon.

Economic development: The role of technological innovation in international trade has begun to receive attention.

Improvement: explains how technology gaps affect international trade, Especially trade between developed and developing countries.

Improvement: Explains the international trade pattern of products from innovation to maturity to decline, The role of innovation in international trade was emphasized.

Economic development: The importance of product innovation and life cycles in international trade.

Time: 1960s, proposed by Raymond Vernon.