Introduction -- General analysis of hub-and-spoke collusion -- Collusion to raise downstream prices : upstream supplier as hub -- Collusion to raise downstream prices : downstream intermediary as hub -- Collusion to exclude rival firms -- General assessment of hub-and-spoke cartels --...

An imperfectly-informed regulator needs to procure multiple units of some good (e.g., green energy, market liquidity, pollution reduction, land conservation) that can be produced with heterogeneous technologies at various costs. How should she optimally procure these units? Should she run...