The advent of the Internet has revolutionized the way companies advertise, develop and distribute products. Firms can now customize their advertising messages and products to the particular characteristics and needs of customers. Customers themselves can create their own products. We investigate...

We propose a new location model where consumers are allowed to make multiple purchases (i.e., one unit from each firm). This model may fit many markets (e.g. newspapers, credit cards) better than existing models. A common feature of these markets is that some consumers are loyal to one brand,...