University of Isfahan International Economics Studies 2008-9643 45 2 2015 10 01 A Perfect Specialization Model for Gravity Equation in Bilateral Trade based on Production Structure 1 8 21968 10.22108/ies.2017.79036 EN Majid Einian Graduate School of Management and Economics, Sharif University of Technology, Iran Farshad Ranjbar Ravasan Paris School of Economics, Paris, France Journal Article 2015 11 10 Although initially originated as a totally empirical relationship to explain the volume of trade between two partners, gravity equation has been the focus of several theoretic models that try to explain it. Specialization models are of great importance in providing a solid theoretic ground for gravity equation in bilateral trade. Some research papers try to improve specialization models by adding imperfect specialization to model, but we believe it is unnecessary complication. We provide a perfect specialization model based on the phenomenon we call tradability, which overcomes the problems with simpler initial. We provide empirical evidence using estimates on panel data of bilateral trade of 40 countries over 10 years that support the theoretical model. The empirical results have implied that tradability is the only reason for deviations of data from basic perfect specialization models.<br /> <strong>JEL Classification:</strong> F11, F14, C23, E23. https://ies.ui.ac.ir/article_21968_603dc38435bbfe8aff2ea8b450e34a30.pdf