What is free trade? Free trade is the international trade of goods and services without tariffs or other trade barriers. Krugman (1987) in Is Free Trade Passé seeks true free trade that depends on perfect competition and constant returns. Nowadays, countries are more likely to follow strategic trade policies that give domestic businesses, households, or factors of production an advantage over foreign ones. The theory of comparative advantage has many assumptions, one of these is that of constant returns, which are the traditional models of international trade. Constant returns are changes in output resulting from a proportional change in all inputs (where all inputs increase by a constant factor). If output increases by the same proportional change, returns to scale are constant. For example, suppose our inputs are capital or labor and we double each of these, our output will be exactly double. Perfect Competition: A market structure characterized by a large number of firms that are so small relative to the overall size of the market that no single firm can influence the market price or quantity traded. Perfect competition and consistent returns go hand in hand; without constant returns, the perfect competition hypothesis becomes very difficult to apply. Nowadays, the idea of ​​constant returns has shifted because according to Krugman (1987) "over the past decade the traditional constant returns, perfect competition of international trade have been complemented and to some extent supplanted by a new generation of models that emphasize increasing returns and imperfect competition" (p. 131). In the modern economy, perfect competition cannot hold because a country is more likely to use increasing returns than constant returns. a half-paper technology that benefits everyone. Even from an economic perspective, free trade provides free and open transactions of goods and services between countries, consumers are able to access more and better goods, and companies are able to able to sell products to more people around the world. I also see that free trade creates an influx of wealth and employment for everyone. On the other hand, some countries can profit more than others through free trade. In conclusion, traditional models in international trade of constant returns to scale and perfect competition have been complemented by new models of increasing returns and imperfect competition. Free trade is not outdated, but it has lost its innocence; free trade is still good police. However, world economics has improved and free trade should improve as well. “Free trade is better than no trade,” as Krugman pointed out.