In the third essay I show that the existence of homogeneous products in a market depends on choices made by firms. If search costs are small or the proportion of consumers who search costlessly (shoppers) is large, firms have incentives to differentiate themselves vertically. On the other hand,...

In the first essay, I analyze a symmetric duopolistic market where each firm's choice regarding certain quality attributes such as the environmental friendliness of its product is its own private information. I find that the extent of horizontal differentiation between firms plays a crucial role...