What's the difference between traditional trade theory and modern trade theory?

Comparison between trade theory and traditional trade theory: mainstream international trade theory: as a special branch of theory, international trade theory began with Adam Smith.

Since 1980s, many western economists have devoted themselves to explaining the phenomenon of international trade with the theories of industrial organization and market structure, and constructed new trade theoretical models with the concepts and ideas of imperfect competition, increasing returns to scale and different products. A group of economists represented by Stiglitz, Krugman, Grossman and Helpmann created a new analytical framework.

The traditional international trade theory has strict logic and perfect form. But this is also its weakness. Because the real world is not as perfect as imagined. In fact, the traditional international trade theory has been severely challenged since its birth. Leontief's fans first questioned his prediction of the pattern of goods and factors in international trade through empirical research.

After the war, especially after the 1960s, many new phenomena appeared in the field of international trade. Trade between developed countries (that is, between countries with similar factor endowments) and between similar products (that is, between products with similar factors needed for production). The traditional international trade theory is at a loss.