Despite a huge investment of research funds over the past 30 years, there has been remarkably little progress towards an agreed theory of fertility transition. As demographic trends unfold, the gulf between certain dominant explanatory models and the raw evidence widens. This attempt to present a framework within which some real progress can be made towards a fuller understanding of the shift from high to low fertility thus starts with a description of what happened to levels of childbearing in developing countries over the past 35 years. As will be shown, there are many obvious lessons to be drawn from a straightforward description.