Population Ecology

Population ecology or natural selection has been considered in social systems since the 1940's, but was best defined by Hannan and Freeman (1977) and Aldrich (1979). It primarily applies to populations of organizations, and tries to explain why some organizational forms survive and others fade away.

They propose that organizational forms with the best fit to environmental characteristics will be selected and proliferate. In natural selection, a variety of forms are created, some are selected for better fit, and the form is retained through reproduction or duplication. They contend that organizations usually don't change or adapt but are replaced by organizations with forms that better fit the current environment. It has become very popular due to its defined and accepted biological paradigm and it's quantitative methodologies.

One important concept from population ecology is density dependence, which suggests that the concentration of a certain organizational form follows a curvilinear approach -- rising legitimacy increases founding rates early on and later competition reduces founding rates.