The Demographic Transition Theory


The demographic transition can be defined as a process where “societies experience modernization and progress from a pre-modern regime of high fertility and high mortality to a postmodern one in which both are low (Kirk, 1996:361). The transition is a worldwide phenomenon and is experienced by every country as it embarks on economic and social development. Since modernization has taken place at different time periods in different regions, the demographic transition has also occurred at different times across the world. The transitions first took place in North Western Europe with a decline in mortality around the 1800s. Eastern and Southern Europe soon followed suit. However, lower income countries did not start their transitions until the early twentieth century and took off especially after the World War II (Lee 2003). A striking fact about the current transitions is the speed by which they are being played out. According to Kirk (1996), the mortality transition took about 75- 100 years in Northern Europe. This decreased to only 20-25 years in Eastern Europe. The current transitions taking place in developing countries are undergoing change even faster.
Another interesting trend is that mortality decline is taking place even in conditions of low income. This is probably because of the spillover effects of advances in medicinal technology and scientific breakthroughs for curing many diseases.
The demographic transition can be classified into 3 stages. In the first phase, both fertility and mortality rates are high. Here, the economy is in a Malthusian trap where any population growth will be kept in control through ‘preventive’ and ‘positive’ checks. The second phase kicks off with a fall in mortality. The mortality decline in the eighteenth century can be attributed to development of the modern state, establishment of law and order which oversaw reduction of deaths from random and local wars (Kirk, 1996). Human longevity is  also a consequence of medical breakthroughs in medicine, improvements in transport and agriculture, which help avert famines and improves nutrition. In almost all the countries where the demographic transition took place earlier, it took place in the conditions of rising incomes. A major difference being experienced in the contemporary transitioning countries is that mortality rates are falling without much increase in income, i.e. income growth is a sufficient but not necessary prerequisite for starting the demographic transition.
Once mortality decline is underway, fertility decline follows next. The causes of fertility decline are much debated upon. Perhaps the most important determinant is the preceding decline in mortality. The basic economic theory of fertility states that every couple wishes to have an ideal number of surviving children. In conditions of high mortality they produce more children. However, in the face of declining mortality, they witness an increase in the number of surviving children and adjust their fertility rates accordingly (Lee, 2003). The impact of contraceptive technology and family planning is contentious. The author of this paper believes that contraceptive technology is simply a tool rather than a cause for declining fertility. Faced with changing preferences and lower mortality, people decline their fertility through all means possible. During the spectacular fertility decline experienced in Japan in the 1950s, a survey showed that around a third of all couples had practiced contraception at some point and sterilization was also widely used (Davis, 1963). While Japan had high tolerance levels of such tools, in places where contraception was looked down upon people responded through other means like late marriage, increased celibacy etc. Of course, there are more dimensions to this debate. Fertility decline is caused by a set of complicated and inter woven factors. However, it will go beyond the scope of this paper to address all the different strands of literature discussing causes of fertility decline.
Fertility decline occurs after mortality decline almost always with a lag of a generation or two. Due to this lag there is a period where the same number of children are being born, however their chances of surviving has increased. Thus the second phase is characterized by rapid population growth and resulting changes in age structure and dependency ratios. The third phase starts when both fertility and mortality rates are low and the population growth stabilizes (Lee, 2003).
In the first stage, the median population age is very young and population growth very low. In the second stage, when mortality falls, there is a population explosion and child dependency ratios rise rapidly. Once fertility levels also fall, the population growth is kept in check. However, this lag has many implications on age structure where there is a generation or two of rapid population growth which gives rise to the term ‘baby boomers’. As these baby boomers transition through different age groups, the age structure of the total population is skewed towards that particular age group. It is when this bulk of population enters the working age group; it is referred to as the demographic dividend. In this case, majority of the population is concentrated in the 15-59 age group and total dependency ratios fall to unprecedented levels. However, in the third phase, as a result of increased life expectancy, the median age goes up and old age dependency ratio grows. At the end of the transition, the total dependency is back to the initial levels, however there are now more elderly than children (Lee, 2003)

Monday, 29th Dec 2014, 10:13:01 AM

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