We build a model of tacit collusion between firms that operate in multiple markets to study the effects of trade costs. A key feature of the model is that cartel discipline is endogenous. Thus, markets that appear segmented are strategically linked via the incentive compatibility constraint....

Short run gravity is a geometric weighted average of long run gravity and bilateral capacity. The model features (i) joint trade costs endogenous to bilateral volumes, (ii) long run gravity as a limiting case of efficient investment in bilateral capacities, (iii) a structural ratio of short run...