Abstract Most international commerce is carried out by multinational firms, which use their foreign affiliates both to serve the market of the host country and to export to other markets outside the host country. In this article, I examine the determinants of multinational firms’ location and production decisions and the welfare implications of multinational production. The few existing quantitative general equilibrium models that incorporate multinational firms achieve tractability by assuming away export platforms—that is, they do not allow foreign affiliates of multinationals to export—or by ignoring fixed costs associated with foreign investment. I develop a quantifiable multicountry general equilibrium model, which tractably handles multinational firms that engage in export platform sales and that face fixed costs of foreign investment. I first estimate the model using German firm-level data to uncover the size and nature of costs of multinational enterprise and show that the fixed costs of foreign investment are large. Second, I calibrate the model to data on trade and multinational production for twelve European and North American countries. Counterfactual analysis reveals that multinationals play an important role in transmitting technological improvements to foreign countries and that the pending Canada-EU trade and investment agreement could divert a sizable fraction of the production of EU multinationals from the U.S. to Canada.

We develop a quantifiable multi-country sourcing model in which firms self-select into importing based on their productivity and country-specific variables. In contrast to canonical export models where firm profits are additively separable across destination markets, global sourcing decisions naturally interact through the firm's cost function. We show that, under an empirically relevant condition, selection into importing exhibits complementarities across source markets. We exploit these complementarities to solve the firm's problem and estimate the model. Comparing counterfactual predictions to reduced-form evidence highlights the importance of interdependencies in firms' sourcing decisions across markets, which generate heterogeneous domestic sourcing responses to trade shocks. (JEL D24, F14, F23, L14, L21)