Abstract
This paper examines a general problem exemplified by post-auction (third generation---`3G') mobile telecommunications markets. When entering these (or any other) markets, firms must often decide on the degree of coverage (`roll-out') they wish to achieve. Prior investment must be sunk in order to achieve the desired (or mandated) coverage level. We study the private and social incentives of a would-be entrant into a market with horizontal product differentiation when choosing its level of roll-out. The endogenous extent of entry influences downstream retail prices; Bertrand or local monopoly pricing or a mixed strategy equilibrium may emerge. Importantly, entry may involve too much or too little roll-out from a social perspective, thus suggesting that regulatory intervention may be appropriate to achieve desired levels of competition in such settings.