Unplanned Purchases and Retail Competition

I propose a framework in which asymmetric multiproduct retailers compete for one-stop shoppers who have biased beliefs about their future purchase probabilities (and so make unplanned purchases). One firm carries a full portfolio of products while the other carries an incomplete but endogenous one. Using this framework, I examine the phenomenon of loss leading, the optimal product portfolio of the smaller firm, and the effects of banning loss leading. Among other results, I show that there is a nonpredatory (and possibly procompetitive) justification for the observation that such larger firms may charge below cost on the core product lines of their smaller rivals.