Although several hypotheses have been proffered to explain changes in the structure and evolution of retailing institutions, none provides a comprehensive explanation of how and why retail institutions evolve. This editorial first introduces the concept of the “Big Middle,” the marketspace in which the largest retailers compete in the long run. It then hypothesizes that these large retailers generally originate as innovators or low-price retailers that focus on a particular niche but migrate into the Big Middle in search of greater revenues and profits. The goal of this editorial is to suggest an initial framework for investigating those factors that create the structure and motivate the evolution of retailing institutions.