This paper examines the importance of buyer-supplier relationships, geography and the structure of the production network in firm performance. We develop a simple model where firms can outsource tasks and search for suppliers in different locations. Low search and outsourcing costs lead firms to search more and find better suppliers. This in turn drives down the firm's marginal production costs. We test the theory by exploiting the opening of a high-speed (Shinkansen) train line in Japan which lowered the cost of passenger travel but left shipping costs unchanged. Using an exhaustive dataset on firms' buyer-seller linkages, we find significant improvements in firm performance as well as creation of new buyer-seller links, consistent with the model.

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.