The Superstar and the Followers: Intra-Firm Product Complementarity in International Trade

This paper investigates whether the exports of different products by the same firm are systematically interconnected. Using Swedish firm-registry data from 1997-2011, I first document that the distribution of firm export sales is skewed towards their best performing products (‘superstars’). I then use a novel instrumental variable approach to identify if the ‘superstar’ products induce more trade of non-superstar products. I find evidence that the exports of low-ranked (non-star) products of a firm complement the exports of a single superstar product to each destination. Extending the ‘superstar’ concept to a ‘superstar core’ of products strengthens this result (this includes the top decile of products in terms of export value). The results show that a 1% increase in the exports of the superstar product and the superstar core increases the exports of non-star products by 0.13% and 0.376%. Hence, I find that the exports of non-star products complements the superstar while conversely, the same complementarity is not found using low-ranked products as placebo-superstars. The main contribution of this paper is identifying a new, sizeable and systematic intra-firm-destination one-way complementarity between products that is missing in the current models of multi-product exporters.