This paper introduces a number of game-theoretic tools to model collusive agreements among firms in vertically differentiated markets. I firstly review some classical literature on collusion between two firms producing goods of exogenous different qualities. I then extend the analysis to a...

In the context of a vertically differentiated duopoly model with endogenous quality choice, we analyzes the welfare effect of overlapping ownership when the market is fully covered. The results show that overlapping ownership, while detrimental for consumer surplus, may increase or decrease...