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...

We examine the relation between consumer search and equilibrium prices when collusion is endogenously determined. We develop a theoretical model and show that average price is a U-shaped function of the measure of searchers: prices are highest when there are no searchers (local monopoly power)...