Policy Research Division Working Paper no. 213. Population policies are deliberately constructed or modified institutional arrangements and/or specific programs through which governments influence, directly or indirectly, demographic change. For any given country, the aim of population policy may be narrowly construed as bringing about quantitative changes in the membership of the territorially circumscribed population under the government’s jurisdiction. Governments’ concern with population matters can also extend beyond the borders of their own jurisdictions. Thus, international aspects of population policy have become increasingly salient. Additions to the population are primarily the result of individual decisions concerning childbearing. Within the constraints of their social milieu, these decisions reflect an implicit calculus by parents about the private costs and benefits of children. But neither costs nor benefits of fertility are likely to be fully internal to the family: they can also impose burdens and advantages on others in the society. Such externalities, negative and positive, represent a legitimate concern for all those affected. The essay briefly discusses how individual and collective interests were reconciled in traditional societies, summarizes the population policy approaches adopted by the classic liberal state, and sketches government responses to the low-fertility demographic regime that emerged in the West between the two World Wars. In greater detail it considers international population policies after World War II and contemporary population policy responses to below-replacement fertility.