This chapter's main aim is to contribute to the study of fertility change through analyzing certain intellectual and institutional aspects of the field of study since World War II. The principal focus is the intellectual history of the idea of demographic transition: the idea that has provided students of changing fertility throughout the postwar era with the dominant collective definition of the phenomenon they are seeking to understand and explain. “Demographic transition” has been confusingly invoked at different times by different authors—or even by the same author at the same time—as theory (“the” demographic transition), historical model, predictive model, or mere descriptive term. All of these uses crop up at various points in the account below. I will make no attempt to adjudicate between them. My aim, rather, is to explain this ambivalence through investigating their joint provenance.

If the postwar intellectual history of the study of changing fertility is intimately bound up with the idea of demographic transition, the institutional history has become deeply involved with the agencies and administration of population policy, the “family planning industry,” as Paul Demeny has christened it. During the 1950s an intellectual orthodoxy concerning the importance of the relationship between national economic development and population growth solidified among social scientists, economic planners, and political leaders in the West and in those nations that looked predominantly to the liberal democracies of the West. Within this orthodoxy, the dominant line of thought has tended to emphasize the extent to which relatively rapid population growth can obstruct the potential for economic growth in less-developed countries.