“…Incidentally, the theoretical literature distinguishes between horizontal and vertical product differentiation involving similar and divergent qualities of product variants, respectively (Reitzes, 1992). Lancastrian and Chamberlinian denote two distinct approaches towards modelling horizontal differentiation (Greenaway, Hine, & Milner, 1995). While the former suggests that consumers aim for a particular combination of attributes in their preferred variety (Lancester, 1979), the latter contends that they aspire to purchase as many varieties as possible of a given product class (Dixit & Stiglitz, 1977;Spence, 1976).…”