Marc Melitz

Marc Melitz introduced his 2003 model to explain how differences in firm-level productivity, known as firm heterogeneity, impact international trade. His theory demonstrated that trade liberalization forces the least productive firms to exit the market. Meanwhile, only the most productive firms can afford the fixed costs to enter export markets.

Before Melitz's 2003 paper, traditional trade models struggled to explain why only a small fraction of firms actually export within the same industry. Melitz incorporated productivity differences into trade models, showing that trade creates "winners" (productive exporters) and "losers" (unproductive domestic firms). This shifted the focus of trade theory from solely countries and industries to individual firms.

Marc Melitz is a prominent American economist and a professor at Harvard University. He is affiliated with both the Harvard Department of Economics and the Harvard Business School. His academic home at Harvard allows him to bridge the gap between rigorous economic theory and international business strategy.

According to the Melitz model, when countries lower trade barriers, the most productive firms expand their market share and begin exporting, while less productive firms go out of business entirely. This process of market selection leads to an aggregate increase in productivity for the entire industry, even if no single firm changes its own technology. It proves that free trade boosts welfare by reallocating resources to the most efficient firms.