We have now developed an image of a set of interacting populations whose numbers are constrained by the speed of founding of new organizations and by social and material processes that set (time-varying) carrying capacities. The last step in model building considers the effects of interactions within and between populations on the growth and decline of numbers in each population. Given a fixed intrinsic growth rate and a set of time-varying factors that determine a carrying capacity, we want to learn how vital rates depend on the density of each population. Before considering specific models of density dependence, we discuss alternative ways to conceptualize the size of an organizational population.
Population bioecology takes for granted that the relevant state space of the process of population growth counts the number of members in the population. For example, studies of predator-prey interactions sometimes analyze counts of rabbits and counts of foxes. In the biotic context, it is reasonable to assume that each rabbit exerts roughly the same demand on the resource environment. Likewise, one fox is pretty much like another. The density of rabbit and fox populations relative to some environmental condition is well expressed by the simple counts of numbers in each population, perhaps adjusting for age and sex distributions.
We often follow a similar strategy of modeling the dynamics of counts of organizations in competing populations. For example, we analyze the effects of the number of craft unions and the number of industrial unions on the rates of founding and mortality in each population. However, the sociological case is more complicated than the biotic one because populations of organizations sometimes exhibit considerable diversity in size among members. For example, some specialist craft unions that we studied had as few as one hundred members; other generalist industrial unions had close to two million members. The addition of a small union may have quite different consequences for existing unions than does the addition of a huge one.
It may be useful to measure the size of an organizational population in terms of the aggregate size of all of its constituent organizations. Continuing with the example of labor unions, virtually all published research on growth and decline in the population of labor unions takes aggregate membership of all unions in the country as the dimension of interest. Sociologists, economists, and labor historians have analyzed fluctuations in the total number of union members in the society or, more commonly, fluctuations in the fraction of the labor force that union members comprise. From this perspective, issues concerning carrying capacities focus on the availability of members and on legal and social constraints on the process of enlisting members. Such research, even when it does not employ the notion of a carrying capacity, recognizes that changes in the social composition of the labor force affect the number of members that could be mobilized by the population of unions at a particular moment. Changes in the industrial composition of the economy and in laws regulating conditions of collective bargaining also affect potential membership in labor unions. From this perspective, the study of unions as organizations is made an ingredient of the study of the labor movement.
We favor the other side of this issue. Although the dynamics of aggregate membership involve interesting social processes, understanding such dynamics is not the only way—or even the best way—to analyze change in the world of labor unions. We think that the number of unions in a society is an interesting sociological variable in its own right. A society in which, say, all union members belong to a single union has a quite different structure from one in which the same number of members are organized into a thousand unions. For one thing, the average and maximum size of unions differ greatly in the two cases; and size is associated with a great many dimensions of internal structure. For another, the totality of collective actions by unions will obviously be more diverse in the second case than in the first.
Our theoretical program attempts to explain variations in organizational diversity in society. Diversity is affected both by the numbers of organizations and organizational forms and by the distribution of resources and members among them. A society with one huge organization of a certain type has a quite different social structure from that of a society with many smaller organizations of the same type even though the aggregate size, in terms of members or resources, may be the same.
In essence, these are issues of concentration, which lie at the center of any attempt to understand the structure of dominance and control in society. Analyzing the causes of concentration requires understanding the processes that affect variations in numbers of organizations and organizational forms as well as processes that affect the distributions of members and resources among them. We focus on rates of founding, disbanding, and merger because these rates control fluctuations in numbers of organizations and organizational forms. So it makes sense to ask how these rates depend on the numbers themselves.
We based our research designs on a strategic bet that there are regularities in the processes that constrain growth and decline in numbers of various kinds of organizations and that analysis of such regularities can illuminate basic processes of organizational ecology.
Source: Hannan Michael T., Freeman John (1993), Organizational Ecology, Harvard University Press; Reprint edition.