Quelch and Kenny note how improvements in supply-side information facilitate the management of product lines. Equally important, however, is demand-side information. Through the careful use of market research, product managers need to answer such questions as: How much cannibalization can we expect if we launch this line extension? Will we see greater sales if we launch this product as a line extension? How many customers will we lose if we drop this stock-keeping unit (SKU)? Cultivating such information is not a simple or cheap exercise. In our own experience, even a “simple” task like using scanner data to measure cannibalization is not as straightforward as it may seem.