Within the heterogeneous independent private values model, we analyze bidder collusion at first and second price single-object auctions, allowing for within-cartel transfers. Our primary focus is on (i) coalitions that contain a strict subset of all bidders and (ii) collusive mechanisms that do...

We introduce capacity constrained competition between market-making intermediaries in a model in which agents can choose between trading with intermediaries, joining a search market or remaining inactive. Recently, market-making by a monopolistic intermediary has been analyzed by Rust and Hall...