Glenn Carroll and Michael T. Hannan (2000) and Logics of Organization Theory: Audiences, Codes, and Ecologies by Michael T. Hannan, Laszlo Polos, and Glenn Carroll (2007), provide the most comprehensive overview of the various theories and methods in organizational ecology. Key concerns Organizational ecology focuses on how social (community) forces affect: rates of creation of new organizational forms rates of demise of organizations and organizational forms the rates of change in organizational forms. Organizational mortality Organizational ecology is concerned with the capacity of the environment to support organizations and the rate of growth and decline of organizations within the environment. Each of these forces is a part of what is called Organizational Mortality. Inertia and change This factor holds that organizations that are reliable and accountable are those that can survive (favored by selection). A negative by-product, however, of the need for reliability and accountability is a high degree of inertia and a resistance to change. A key prediction of organizational ecology is that the process of change itself is so disruptive that it will result in an elevated rate of mortality. Theories about inertia and change are fundamental to the research program of organizational ecology, which seeks a better understanding of the broader changes in the organizational landscape. Both internal and external resistance to change can result in organizational inertia, providing some resistance to organizational adaptation. Given the limits on firm-level adaptation, most of these broader changes thus come from the entry and selective replacement of organizations. Hence organizational ecology has spent considerable effort on understanding the founding and mortality rates of organizations. Hannan and Freeman define organizational inertia in terms of internal and external restraints. Internal restraints include investment and sunk costs; availability of information for decision makers; political restraints such as organizational culture; and organization history. External restraints include legal and fiscal barriers to market entry and exit; availability of information about the environment; external legitimacy; and collective rationality and strategy (See also Bounded rationality). Niche theory Niche width distinguishes broadly between two types of organizations: generalists and specialists. Generalist organizations maximize their exploitation of the environment and accept the risk of experiencing a change in that environment. On the other hand, specialist organizations accept a lower level of exploitation in return for greater security. Niche theory shows that specialization is generally favored in stable or certain environments. However, the main contribution of the niche theory is