This paper expands on Kingsley Davis's demographic thesis of change and response. Specifically, we consider the social context that accounts for the primacy of particular birth control methods that bring about fertility change during specific time periods. We examine the relevance of state policy (including national family planning programs), the international population establishment, the medical profession, organized religion, and women's groups using case studies from Japan, Russia, Puerto Rico, China, India, and Cameroon. Some of these countries are undergoing the second demographic transition, others the first. Despite variations in context, heavy reliance on sterilization and/or abortion as a means of birth control is a major response in most of these countries. The key roles of the medical profession and state policy are discussed, along with the general lack of influence of religion and of women's groups in these countries.Keywords: birth control, fertility change, social context, medical profession, state policy, religion, women's groups Kingsley Davis's 1963 presidential address to the Population Association of America offered a new perspective on demographic change: its 'multiphasic' nature. Stimulated by marked declines in mortality and resulting high levels of natural increase, countries that had undergone significant economic development responded in 'almost every demographic manner then known….Within a brief period they quickly postponed marriage, embraced contraception, began sterilization, utilized abortions, and migrated outward' (Davis 1963: 349). Davis provided data for Japan and several Northern European countries to demonstrate the inappropriateness of focusing on single responses, such as the high rate of abortion in Japan or the late ages at marriage in Ireland. (It would have been more appropriate to call these responses multifaceted rather than multiphasic, since the particular sequencing of responses and explanations for such patterns were not discussed.) Davis's focus on multiple † Address