An account, but not a complete explanation, of changing rates of fertility, mortality, and natural increase. Four stages may be recognized: in the High Stationary Stage, birth and death rates are high and the death rate fluctuates from year to year; the Early Expanding Stage is characterized by high birth rates, falling death rates, and increases in population; in the Late Expanding Stage death rates are low and fertility is declining, but population is still increasing; and, lastly, in the Low Stationary Stage birth and death rates are low and the birth rate fluctuates. There seems to be a fifth stage where birth rates fall below death rates so population levels fall.

Death rates fall because of improved conditions and health care. The reasons for falling fertility are less clear, but include: anti-child labour laws; pensions (which remove the need for children as a support in old age); a higher proportion of women in work; and increasing costs of bringing up children, as standards of living rise. Everywhere, mortality decline appears to have played a central role for fertility decline. ‘Female literacy and aggregate income do not seem to matter as much’ (Conley et al. (2007) NBER W. Paper 2892). Reher (2004) Pop. Space Place 10, 19 notes that, with falling child death rates, fertility falls rapidly in the developed world, and more slowly in more recent transitions. In an analysis of developing countries, Zlidar et al. (2003) Pop. Reports, M 17 note that fertility has fallen by an average of 1% per year, due to increased contraception use, better child survival rates, and better maternal health care. Because of their late start to the DTM, developing countries will not catch up demographically with more developed regions for over 200 years: ‘in fact, less developed regions never seem fully to catch up’ (UN Dept. Econ. & Soc. Affairs, Pop. Division). See McNicoll (2006) Pop. & Dev. Rev. 32, 1 on politics and the East Asian demographic transition. ‘The end of the transition is also the end of the explanatory paradigm, and no other paradigm is, at present, capable of enlightening us on the future’ (Vallin (2002) Pop. & Dev. Rev. 28, 1).

The second demographic transition is marked by: a later age at marriage; an increase in the proportion of adults living alone or cohabiting; slower rates of remarriage; increased fertility outside of marriage; and delaying or forgoing childbearing. ‘With respect to timing, process, and explanation, the second demographic transition is characterized by no less diversity than the historical first transition’ (Lesthaeghe and Moors (2000) Rev. Pop. & Soc. Policy 9).