Burgess studied the history of development and concluded that the city had not grown at the edges. Although the presence of Lake Michigan prevented the complete encirclement, he postulated that all major cities would be formed by radial expansion from the center in concentric rings which he described as zones, i.e. the business area in the center, the slum area (called the zone in transition and studied by Wirth: 1928, Zorbaugh: 1929, and Suttles: 1968) around the central area, the zone of workingmen's homes farther out, the residential area beyond this zone, and then the bungalow section and the commuter's zone on the periphery. Under the influence of Albion Small, the research at the school mined the mass of official data including census reports, housing/welfare records and crime figures, and related the data spatially to different geographical areas of the city.