[24]. Report of the Chicago Subway and Traction Commission, p. 81, and the Report on a Physical Plan for a Unified Transportation System, p. 391.
[25]. Data compiled by automobile industries.
[26]. Statistics of mailing division, Chicago Post-office.
[27]. Determined from Census Estimates for Intercensal Years.
[28]. From statistics furnished by Mr. R. Johnson, traffic supervisor, Illinois Bell Telephone Company.
[29]. From 1912–23, land values per front foot increased in Bridgeport from $600 to $1,250; in Division-Ashland-Milwaukee district, from $2,000 to $4,500; in “Back of the Yards,” from $1,000 to $3,000; in Englewood, from $2,500 to $8,000; in Wilson Avenue, from $1,000 to $6,000; but decreased in the Loop from $20,000 to $16,500.
[30]. Nels Anderson, The Slum: An Area of Deterioration in the Growth of the City; Ernest R. Mowrer, Family Disorganization in Chicago; Walter C. Reckless, The Natural History of Vice Areas in Chicago; E. H. Shideler, The Retail Business Organization as an Index of Business Organization; F. M. Thrasher, One Thousand Boys’ Gangs in Chicago; a Study of Their Organization and Habitat; H. W. Zorbaugh, The Lower North Side; a Study in Community Organization.
[31]. Encyclopedia Americana, New York (1923), p. 555.
[32]. As indicated later on in this paper, ecological formations tend to develop in cyclic fashion. A period of time within which a given ecological formation develops and culminates is the time period for that particular formation. The length of these time periods may be ultimately measured and predicted, hence the inclusion of the temporal element in the definition.
[33]. The word “position” is used to describe the place relation of a given community to other communities, also the location of the individual or institution within the community itself.