The structuring of organizational populations

I construct theoretical models of the founding, failure, and growth of orga nizations that, when combined, constitute an explanation of the process by which the number of organizations in a population (the population density) declines from a peak, while at the same time the population mass (the aggre gate size of the organizations in the population) continues to increase. Em pirical results from, analyses of the vital rates of credit unions in New Y ork City are generally supportive of the models. The results of computer si mulations are consistent with empirically observed trajectories of density and mass for the credit union data.