When examined over long periods of time, counts of the number of organizations in diverse populations initially grow slowly, then grow rapidly for a short time, peak, then decline and stabilize (and often eventually decline). This project continues a line of research that seeks to explain this pattern by means of developing a set of mathematical models based on a sociological theory of density-dependent evolution, that is, the pattern of the birth, growth, decline, and mortality of organizations as a function of the number of organizations in a population. Among the new issues that are being confronted by this project are the disentanglement of the effects of age versus size of organizations and of density versus mass of populations and the application of density theory to the community level as well as to individual populations. Data will be collected on populations and communities of financial institutions and newspaper publishing firms to examine these issues empirically. This project will not only contribute to our understanding of the forces shaping organizational structures over long time spans, but also it will contribute to the provision of a theoretical structure for explaining how organizational change produces changes in society.
