This article explores new ways to model international trade in economic models. They look at different theories that focus on how companies compete in global markets. By studying these theories, the researchers hope to make it easier for others to understand and use them in computer models. One key theory they focus on is about firms with different sizes and export behavior. The researchers found that this theory is important for predicting the effects of economic integration and climate policies. By using this theory in their models, they discovered that it can lead to more variety in products and better productivity. They also saw that climate policies could change trade patterns, impacting emissions and international trade.