Population theories (cont'd)
By A. Swaby-Burton, Contributor

IN THIS week's lesson, emphasis will be placed on the theory of 'Demographic Transition'.

Demographers often refer to the changes in the ratio of births to death in industrialised countries from the 19th century onwards as the demographic transition. The term was first coined by Warren S. Thompson, who described three processes through which one type of population stability is eventually replaced by another.

The theory of demographic transition holds that the growth rate of a population tends to stabilise once a certain level of economic development is achieved, primarily because people in urban industrialised societies prefer small families and voluntarily limit the number of their
children. In these modern times, children are not an economic asset at all; to feed and educate them places a considerable burden on the parents, but yields no economic rewards.

According to demographic transition theory, people generally tend to have as many children as they believe they can support. The problem in developing societies, then, is that peoples attitudes have not yet caught up with their rapidly changing circumstances.

As stated earlier, the demographic transition appears to proceed in three basic stages:

STAGE ONE

This is the situation found in all traditional societies. There is a high birth rate and a very high death rate, especially among infants. As a result, population numbers remain fairly stable.

STAGE TWO

This began in Europe and the United States in the early part of the 19th century with wide regional variations occurring when death rates fell, while fertility remained high. This is subsequently as a result of improved living standards and medical care. As a result population grows very rapidly.

STAGE THREE

This is the situation found in advanced industrial societies. The birth rate drops as families come to be seen as a liability, and the death rate remains low. As a result, the population growth rate gradually declines towards zero and remains fairly stable.

Trends since early modern times:- the model of demographic transition.

Demographers estimate that the world population reached 500 million by about 1650. From this time population grew at an increasing rate. By 1830 globally population had doubled to reach a billion.

Although no two country's populations have changed in the same way, some broad generalisations can be made about population growth since the middle of the 18th century. These generalisations can be seen by the diagram of the demographic transition below.

No country as a whole retains the characteristics of stage 1; which apply only to the most remote societies on earth such as isolated tribes in New Guinea. At present all the developed countries of the world are now in stage 4; most have experienced all the other stages at different times. The poorest of the developed countries example Bangladesh, Niger, Bolivia are in stage 2, but are joined in this stage by the rich Middle East states where increasing influence was not accompanied by a significant fall in fertility. Most developing countries which have registered significant social and economic advances are in stage 3 for example Brazil, China, Turkey, while some of the new industrialised countries such as South Korea and Taiwan have just entered stage 4. With the passage of time there can be little doubt that more countries will attain the demographic characteristics of the final stage of the model.

Stage 4 ­ has been added to the previous stages as countries have experienced demographic transitions. Stage four is referred to as the low fluctuating stage; both birth and death rates are low. Birth rates were formerly higher, fluctuating somewhat due to changing economic conditions. Here population growth is very slow and may even be negative if the birth rate falls below the death rate. Death rate tends to rise slightly as the average age of the population increases. Despite this, life expectancy still improves as age specific mortality rates continue to fall. This stage completes the population cycle according to this model, but will a stage 5 significantly prolong natural increase? See Figure 1

The Demographic Transition Model.

Figure 2:

Adapted from: Advanced Geography (Paul Guiness and Garrett Nangle).

TYPES OF DEMOGRAPHIC TRANSITION

The Czech demographer Z. Paulik has recognised three types of demographic transition. Apart from the 'classical or English type' described above, he also refers to the 'French' and Japanese - Mexican types. See diagram below. In France the birth and death rates diminished at a similar pace and there was no intermediate period of high natural increase. In Japan the birth rate actually increased in stage 2 due largely to the improved health of women in the reproductive age range. Join me next week as I continue to explore population issues.