Thus, for Burgess the characteristics of the social organization of the urban population were spatially deployed. The extensive use of mapping is supposed to reveal the spatial distribution of social problems. It was found that individual traits such as mental illness, gang membership, criminal behaviour, and racial background were found to be clustered along the centre/periphery gradient of the city. Using the census data, the Chicago researcher showed that the incidence of social pathology decreased from the central business district to the outskirts, whereas homeownership and the number of nuclear family increased. The inner zones, therefore, were discovered to be the sites of crime, illness, gang warfare, broken homes and many other indicators of social disorganization or problems.