Carry-Along Trade
研究发现比利时制造业企业大量出口自己不生产的产品（携带贸易），且该行为随生产率提高而增加，并提出了包含需求范围互补性的理论模型。
Large multi-product firms dominate international trade flows. Using novel linked production and export data at the firm-product level, we find that the overwhelming majority of manufacturing firms export products that they do not produce. Three quarters of the exported products and 30% of export value from Belgian manufacturers are in goods that are not produced by the firm, so-called Carry-Along Trade (CAT). The number of CAT products is strongly increasing in firm productivity while the number of produced products that are exported is weakly increasing in firm productivity. We propose a general model of production and sourcing at multi-product firms and explore new demand- and supply-side modelling features capable of generating predictions consistent with the empirical findings. Export price data and company interviews offer suggestive evidence for the presence of demand-scope complementarities.