Tariff Transmission Across US Customs Districts: Product‐Level Evidence From Successive Trade Shocks

ABSTRACT

This paper asks how US tariffs on Chinese imports reshape trade across the nation's customs districts, and whether a district's earlier reliance on China shapes how deeply its imports fall. We build a monthly panel of HS6‐level US imports from eleven source countries arriving through eight customs districts between January 2017 and December 2025, and estimate product‐specific import‐demand elasticities by Poisson Pseudo‐Maximum Likelihood with three‐way high‐dimensional fixed effects. The estimated elasticity, which we interpret as a conditional import‐demand response among observed foreign suppliers rather than a fully structural Armington parameter, is substantially larger than earlier nationally aggregated studies have reported. This gap matters because it suggests that aggregation across entry points and product categories has long hidden how severe the trade destruction really is. Districts heavily dependent on Chinese imports before the tariff wave experience much sharper declines than less‐exposed ports. The pattern is sharpest for differentiated goods in which Chinese suppliers had already dominated before the tariff hit, where no obvious alternative source stands ready to absorb displaced demand. A further decomposition separates the contemporaneous response from anticipatory pre‐positioning and shows that a nontrivial share of what has been called the static elasticity actually reflects firms acting on expectations of future tariffs. Trade diversion flows mainly towards ASEAN economies, and distance plays essentially no role.