Gravity Without Apology: the Science of Elasticities, Distance and Trade
回顾了贸易随距离下降的实证证据，介绍了常替代弹性重力理论作为一般均衡系统的解释工具，指出常贸易弹性假设的异常和双边贸易平衡的不合理预测，并提出了亚凸重力作为解决方向。
Abstract Gravity as both fact and theory is one of the great success stories of recent research on international trade, and has featured prominently in the policy debate over Brexit. We first review the facts, noting the overwhelming evidence that trade tends to fall with distance. We then introduce some expository tools for understanding constant-elasticity-of-substitution theories of gravity as a simple general-equilibrium system. Next, we point out some anomalies with the theory: mounting evidence against constant trade elasticities, and implausible predictions for bilateral trade balances. Finally, we sketch an approach based on subconvex gravity as a promising direction to resolving them.