Do state borders matter for U.S. intranational trade? The role of history and internal migration

Abstract.  Empirical evidence of the impact of borders on international trade flows using the gravity equation approach abounds. This paper examines the empirical relevance of state borders in U.S. interstate trade for various specifications of the gravity equation. We find a large and economically significant subnational border effect for some specifications. However, two model specifications drastically reduce (if not eliminate) the border effect: (i) dynamic panel specifications controlling for past levels of trade and (ii) models conditioning on internal migration.