Multi-product firms in international economics

A striking pattern in transaction-level data is the concentration of international shipments in the hands of a few large firms. One common feature of dominating high-performance firms is that they produce multiple products and ship them to many destinations. Motivated by the emergence of highly detailed data at the firm-product-destination level, a series of theoretical and empirical papers studies the role of multi-product firms (MPFs) in international trade. This survey reviews the evidence on the importance of MPFs in international markets and highlights the key theoretical as well as empirical results that the literature has produced in the last decade.