Barriers to international trade are known to be large but due to data limitations it is hard to measure them directly for a large number of countries over many years. To address this problem I derive a micro-founded measure of bilateral trade costs that indirectly infers trade frictions from observable trade data. I show that this trade cost measure is consistent with a broad range of leading trade theories including Ricardian and heterogeneous firms models. In an application I show that U.S. trade costs with major trading partners declined on average by about 40 percent between 1970 and 2000, with Mexico and Canada experiencing the biggest reductions.

Many studies have found that international borders represent large barriers to trade. But how do international borders compare to domestic border barriers? We investigate international and domestic border barriers in a unified framework. We consider a data set of exports from individual U.S. states to foreign countries and combine it with trade flows between and within U.S. states. After controlling for distance and country size, we estimate that relative to state-to-state trade, crossing an individual U.S. state’s domestic border appears to entail a larger trade barrier than crossing the international U.S. border. Due to the absence of governmental impediments to trade within the United States, this result is surprising. We interpret it as highlighting the concentration of economic activity and trade flows at the local level. JEL classification: F10, F15

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