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. (JEL D11, D21, D83, L13, L25, L71, L81)