Recent literature sets forth the positive role of migrants in international trade and foreign direct investment. We use a new database on French migrant associations together with data on the stocks of migrants to diffe-rentiate between organized and, respectively, non-organized migrant-based networks. We find that the creation of a new association of migrants is accompanied by important jumps in bilateral trade and investment between the host and origin countries. This effect adds on top of the impact of non-organized migrant communities, documented in the literature. Non-organized networks affect trade via preference and information channels, while organized networks play mainly an informational role.* tation costs (both in terms of freight and time), 8% for policy barriers (tariffand non-tariff barriers), 14% for currency barriers, and 17% for inferred trade costs, such as information costs, contract enforcement costs, legal and regulatory costs, etc. (1.74 = 1.21 x 1.08 x 1.14 x 1.17). Despite the recent innovations in technology associated with lower transport costs, the authors estimate that they still represent the largest share of international trade costs. Given the recent trend of global trade liberalization, the friction induced by tariffand non-tariff barriers (NTB) has also declined. The barriers caused by the use of different currencies in the importing and exporting country are large, but very difficult to reduce due to major macroeconomic costs1. The present paper focuses on inferred trade costs. RAUCH (2001) identifies these costs as information and partner search costs, institutional costs (costs relative to the poor quality of do- mestic importer and/or exporter institutions), and contract enforcement costs (costs resulting from risk and uncertainty with regard to the outcome of international transactions (ANDERSON and MARCOUILLER (2002)). As suggested by their name, hidden transaction costs are not easily quantified or even revealed, and they make international trade contracts more time-demanding, 1 . Developing and transition countries have linked their domestic currency to a hard foreign currency and reduced exchange rate volatility almost exclusively in periods of harsh economic problems. European Monetary Union was achieved at a high cost and after a long history of economic integration.