Universal Gravity
研究了一类一般均衡贸易与地理模型的理论性质，证明存在性、唯一性及反事实预测仅取决于需求与供给弹性（引力常数），并估计这些常数以计算中美贸易战的影响。
We study the theoretical properties and counterfactual predictions of a large class of general equilibrium trade and economic geography models. By combining aggregate factor supply and demand functions with market-clearing conditions, we prove that existence, uniqueness, and—given observed trade flows—the counterfactual predictions of any model within this class depend only on the demand and supply elasticities (“gravity constants”). Using a new “model-implied” instrumental variables approach, we estimate these gravity constants and use these estimates to compute the impact of a trade war between the United States and China.