The Option of Joint Purchase in Vertically Differentiated Markets.

Within the framework proposed by Mussa and Rosen (1978)for mod- elling quality di .erentiation,we allow consumers to buy simultane- joint purchase .We show that this option dramatically a .ects price competition:while a unique equilibrium always prevails when consumers are assumed to make mutually exclusive purchases,either uniqueness,or multiplicity,or absence of price equilibrium arise when the joint purchase option is opened depending on the utility attached to joint purchase relative to separate purchases.ously di .erent variants of the same indivisible good.We call this the