Size and the Density of Interaction in Human Aggregates

A baseline model is developed to show the conduciveness of population size to the density of interaction in human aggregates. This model permits deduction and, therefore, explanation of a wide variety of social phenomena. It explains the positive relation between rates of crimes of violence and city size indicated by Webb's (1972) data. And it provides a formal rationale for Kasarda's (1974) hypothesis relating size and communication in macrostructures, as well as an alternative to some aspects of the theory formulated by Hamblin, Jacobsen, and Miller (1973). Our model accounts for the "transitory" and "superficial" nature of urban social relations commented upon by Simmel (1903), Wirth (1938), and Milgram (1970) and explains why inhabitants of large cities are unlikely to intervene in crises. In conjunction with considerations noted by Mayhew et al. (1972), the model explains why role strain may be expected to increase with organizational size, as illustrated in Snoek's (1966) national study. The wide variety of phenomena illuminated by this model suggests that it is a serious mistake to view the effects of population size as "obvious." Rather, taking population size explicity into account should enhance the explanatory power of sociological theories.