Score contribution per author:
α: calibrated so average coauthorship-adjusted count equals average raw count
We point out a fundamental difficulty of successfully colluding in retail markets with heterogeneous firms, and characterize the mechanism recent gasoline cartels in Canada used to sustain collusion. Heterogeneity in cost and network size necessitates arrangements whereby participants split the market unequally to favor stronger players. We characterize empirically the strategy and transfer mechanism using court documents containing summaries and extracts of conversations between participants. The mechanism implements transfers based on adjustment delays during price changes. We estimate that these delays can translate into substantial transfers and provide examples in which they can substantially reduce deviation frequency.