There are several analytical strands through which historians and demographers understand the evolution of twentieth-century population politics and expertise. One is the history of the declining birthrate, nationalism, pro-natalism, and modern degeneration anxieties, including histories of eugenics. A second strand is the story of global overpopulation, its mobilization as a mid-twentieth-century issue in Cold War politics, the dominance of the idea of demographic transitions and political economy, and subsequent links between aid, development, family planning, and various international agencies. A third is the history of reproductive and bodily rights, feminism, and birth control, which has been analyzed with respect to the history of technology, the history of colonialism and neo-colonialism, the history of nationalism, and to some extent the history of internationalism. The political economy aspects of the population question tend chronologically to bookend the feminist narrative, with Malthus at the late eighteenth-century end and Cold War political economy of third world development at the twentieth-century end. A fourth strand is a burgeoning intellectual history of demography, social science, and economic theory.