POPULATION SIZE AND DEMOGRAPHIC TRENDS
a. Changes in Population
The people of a country are its consumers. They provide the labour force for production. A study of the population of any country, therefore will give a bird's eye view of the community for which the economic system must provide, and also of the size and nature of the available labour force. At any one time the structure of the population is largely the result of demographic factors prevailing some fifty years earlier. In Africa, the improvements in medical knowledge and increased application of that knowledge have been able to produce dramatic reductions in death rates, so that the average life expectancy in Africa may well have been doubled over the past half-century, application of the improvements in technical knowledge has not been able to produce equally dramatic changes in the supply of food.
b. Causes of changes in the Rate of Growth
Changes in population come about in two ways; (i) by movements in crude death rates, and (ii) by migration. The crude birth rate is usually expressed as the number of births per annum per thousand of the population and the crude death rate is the number of deaths per thousand of the population per annum. The natural growth rate will be the difference between these two rates,
Natural Growth Rate = Birth Rate - Death Rate
Thus if a country has a birth rate of 40 per 1000 and a death rate of 20 per 1000, its population has a natural growth rate of 2 per cent per annum. The actual rate of population growth is calculated by adjusting the natural growth rate by the extent of net immigration or emigration.
Movements in crude birth and crude death rates has been the most important factor in population development of East Africa countries. The factors which have led to high natural growth rates in East Africa can be summarized as:
- Declining mortality rates,
- High fertility levels,
- Low marriage age,
- Rapidly growing number of women who are in and about to enter the child bearing age because of young populations.
The current trends in world population have revived interest in the population theories of Rev. Thomas Robert Malthus, whose "Essays on the Principles of Population (1978) led to the first serious discussion of the problem. Malthus wrote at a time when the British population was increasing rapidly and the basis of his theory was that whereas population tended to grow at a geometric rate (by a constant and percentage each period, as for example, 4,6,16,24,32,40,48...), the food supply could only be expected to grow at an arithmetic rate (by constant amount each period, as for example 8, 16, 24, 32,40,48...). His observations seemed to confirm his views that increasing numbers could only increase the misery of the masses.
He declared that population has a persistent tendency to outstrip the means of subsistence. Any rise in the living standards of the masses of the people would lead to earlier marriages, more deaths, and more babies surviving. The increased numbers would simply lower living standards back to the bare subsistence level. His purpose was to demonstrate that the increase in population is necessarily limited by the means of subsistence. That population does not invariably increase when the means of subsistence increase and that the superior power of population is repressed, and the actual population kept equal to the means of subsistence by misery and vice versa.
- The checks on population which Malthus summarized as misery and vice versa were famines, plagues, wars and infanticide. He was, off course concerned with the British problem and believed that agricultural output could not possibly increase at the rate at which population tends to grow. In this he was undoubtedly influenced by the Law of Diminishing Returns because he saw the supply of land as relatively fixed. He was proved wrong in the case of Britain for the population quadrupled during the nineteenth century. Malthus' predictions about population have not occurred because:
- He did not consider the tremendous improvements in agricultural and food technologies such use of chemical fertilizers, hybrid seeds an insecticides, and modern irrigation systems to increase land productivity. Famine such as occurred in Ethiopia, Mozambique and many African countries is explained by political instability or inadequate or lack of a clear food policy, not population explosion as suggested by Malthus.
- Malthus did not consider that industrialisation by its very nature would reduce population growth.
- He did not foresee the great improvements in transport and technology which enabled the British people to be fed from the vast lands of the new continents.
- Malthus did not consider that agricultural land area would be increased by reclaiming land from rivers, lakes and oceans.
- Finally he did not foresee that rising standards of living would bring falling birth rates as they did in most Western nations after 1870
Nevertheless the germs of truth in his doctrines are still important for an understanding of the population problems in much of Africa where as we said before, the balance between the numbers of people and the means of subsistence is often precarious. Where inexpensive science greatly reduces the death rate without increasing productivity Malthus still has some relevance.
John Stuart Mill
Mill developed and refined the "Malthusian " theory in order to generalize the relationship between the supply of labour (population) and supply of food from land. This generalization is known as the "Law of Diminishing Returns, sometimes called the Law of Variable Factor Proportions".