Competition and Collusion with Strategic Inventories

We study collusive agreements in an infinite-horizon model in which firms invest in inventories of intermediate goods and compete in quantities of final goods. Stocks of inventories act as capacity constraints at the time of production but can be replenished for future use through investment. Input stocks simultaneously impact firms' ability to deviate from collusive agreements and their ability to punish such deviations and therefore have ambiguous effects on the sustainability of collusion. We characterize subgame perfect equilibria in grim trigger strategies in which firms potentially hold asymmetric excess inventories on the collusive path. We show that the sustainability of collusive agreements is non-monotone in inventory stocks. While holding excess capacity is costly and unproductive, the practice can improve firms' ability to sustain anticompetitive agreements.