Per-Shipment Costs and the Lumpiness of International Trade
利用美国和西班牙的详细出口数据，发现每批运输成本与国际贸易中更少但更大的运输批次（即更块状）相关，这一现象普遍存在于各类产品中，尤其在工业用品、零部件和食品中最为明显。
Using detailed U.S. and Spanish export data, we document that trade costs of a per-shipment nature are associated with less frequent and larger shipments (i.e., more lumpiness) in international trade. This finding is pervasive across broad product categories, but most apparent for industrial supplies, parts and accessories, and food products.