This paper shows that the possibility of collusion between an agent and a supervisor imposes no restrictions on the set of implementable social choice functions (SCF) and associated payoff vectors. Any SCF and any payoff profile that are implementable if the supervisor's information was public...

In markets where sellers' marginal costs of production have a common component, they have informational advantage over buyers regarding those costs. This information asymmetry between sellers and buyers is especially relevant in markets where buyers have to uncover prices through costly search....