This paper develops a general equilibrium model of international trade with heterogeneous exporters and heterogeneous importers. This theory is guided by new findings drawn from a matched exporter-importer dataset that characterizes the relationships between exporting and importing firms. I find that most exporters have a single importing partner, that highly productive exporters tend to trade with highly productive importers, and that the value traded is positively correlated with both exporter and importer productivities. The model analyzes the selection of exporters and importers into trading pairs and features simultaneous free entry into exporting and into importing. This theory provides a rationale for the fixed costs of entering export markets, associating them with the costs of searching for importing firms that distribute a product to final consumers abroad. I test this theory by studying the response of exporting and importing firms to the recent Colombia-U.S. free trade agreement. This evidence illustrates a novel mechanism of adjustment of U.S. firms to trade liberalization.

本文建立了一个具有异质出口商和异质进口商的国际贸易的一般均衡模型。该理论由匹配的进出口商数据集得出的新发现指导，该数据集描述了进出口公司之间的关系。我发现大多数出口商只有一个进口伙伴，高生产率的出口商倾向于与高生产率的进口商进行贸易，而交易的价值与出口商和进口商的生产率均呈正相关。该模型将进出口商的选择分析成交易对，并具有同时自由进入出口和进口的功能。该理论为进入出口市场的固定成本提供了依据，使他们与寻找将产品分销给海外最终消费者的进口公司的成本相关联。我通过研究进出口公司对最近的哥伦比亚-美国自由贸易协定的反应来检验这一理论。这一证据说明了一种调整美国公司以适应贸易自由化的新颖机制。