Demographic Transition

The term demographic transition describes the movement of a society from a situation of high mortality and high fertility (average number of children a woman typically has over her lifetime) to one of low mortality and low fertility. It is typically characterized as a process of reductions in mortality rates followed by, after some delay, reductions in fertility. In the initial period of reductions in mortality without reductions in fertility, there is fast population growth, which is progressively slowed down as fertility starts to decline and the population momentum slows down. In the last stage, faced today by many developed and developing nations, mortality reaches low levels, and fertility stabilizes below replacement rate, leading to reductions in the size of the population in the long run.

The demographic transition is a virtually global pattern. It is probably the best documented social phenomenon in the history of modern societies, and there is a strong consensus regarding its main features. Its generality as a worldwide transformation, and its profound implications in terms of social changes, were noticed long ago by Warren S. Thompson and Adolphe Landry. In stark contrast with the post–World War II catastrophic predictions of the population explosion theorists, these first authors seemed to think of the different stages of the transition as different phases in the process of development and as a process that would eventually spread through most of the world.

Today, the demographic transition is a widespread phenomenon. Unprecedented mortality reductions have reached virtually every corner of the globe—with the exception of sub-Saharan Africa—and the vast majority of human population lives in countries where fertility has already shown significant declines and where population is expected to stabilize by mid-21st century. Major demographic changes swept the world in the course of the past hundred years. Life expectancy at birth rose from 40 years to above 70 in developing countries and to around 80 in the developed world. Total fertility rates dropped from 6 points or above to close to 2 points or below.

In various cases, this process of social change has culminated in extremely low fertility rates, with family sizes below the level necessary to keep [Page 381]population constant in the long run. Although this phenomenon has been associated mostly with western Europe (e.g., in Belgium, Germany, Italy, and Spain), it is not restricted to it. Today, over 70 countries, comprising more than half of the world population, have fertility rates below replacement level. Several developed and developing countries—as culturally diverse as Austria, Canada, China, Croatia, Cuba, Greece, Japan, Russia, and Spain—already face extremely low fertility rates, substantially below the cutoff level of 2.1 points.

In the demographic and economic literature, the demographic transition is also seen as marking the movement between two regimes: the Malthusian regime (or equilibrium) and the modern demographic regime. In the Malthusian regime, societies are thought to be predominantly agricultural, and fertility is supposed to respond positively to improvements in living conditions. So increases in population, with a fixed supply of land, lead to deteriorations in living conditions and, therefore, through positive and negative checks, to a halting of population growth. In this Malthusian world, living conditions cannot improve in the long run, because any gain is “consumed” by population expansion. In the modern demographic regime, on the other hand, fertility is not thought to increase with improvements in living conditions. As the theory goes, in this situation families spend resources on their children and, through a quantity-quality trade-off, increases in income lead to reductions in the size of families but increased human capital of children (investments in education and health). Investments in human capital and the negative relationship between income and fertility open up the possibility of sustained growth with stable or declining population, through increased productivity and technological innovation.

...