Consumers are faced with an increasing number of choices of ever-greater complexity, while, for companies, creating strong brands has become a management imperative. A recurring topic that links both of these considerations is the process by which new brands are introduced into existing product classes. Many of the generalizations about consumer brand choice were established by the work of Andrew Ehrenberg and his colleagues who point out that most consumers are not brand loyal, in the sense of purchasing a single brand 100% of the time; rather, the typical consumer of a product class buys a number of brands over time (sometimes even on the same shopping trip) (Ehrenberg, 1988). Products from this group of tried and tested brands, which is a subset of the brands that comprise the entire product class, are purchased apparently randomly (though in practice often in a structured manner) and are treated as though they were functionally equivalent. That is, the physical properties of each brand in the product class are sufficiently similar that they are closely substitutable. Each consumer’s establishment of a particular consideration set of appropriate brands reflects this substitutability based on functional correspondence.