20 Theories of Population Growth

Gautam Kshatriya and Mamta Kumari Thakur

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Contents:

    1.      Malthusian Theory of Population growth

1.1 Preventive Checks

1.2 Positive Checks

1.3 The theory propounded by Malthus can be summed up in the following propositions

1.4 Criticism of Malthusian Theory

2.      Thomas Doubleday’s Diet Theory

2.1 Doubleday divides society into three groups

3.      Jouse De Castro’s Protein Consumption Theory

4.      Michael Thomas Sadler’s Destiny Theory

5.      Herbert Spencer’s Biological Theory

6.      Corrado Ginnis’s Biological Population Theory

7.      Dumont’s Theory of Social Capillarity

8.      Karl Marx’s Theory of Surplus Population

9.      Leibenstein’s Motivational Theory of Population Growth

 

Learning Objectives:

  • To understand the various theories proposed in the context of population growth.
  • To study the historical theories and assumptions that have been generated by other means in the contemporary world.

    Introduction

 

Population growth is the rise in the number of individuals in a population that reside in a state, country or city. Identifying underlying causes for population growth helps to make better predictions about future changes in population rising and growth rates. Population growth appears today as the major factor determining underdevelopment and population control is advocated as the most urgent and necessary step if development is to be eventually achieved.

 

Theorizing about population size and change has remained an important discipline since long back. Many of the philosophers from history like Confucius (China), Kautilya (India) and modern thinkers like Adam Smith, David Richard etc. have made significant contribution on population rising, where there was no consensus.

 

Following were the population theories proposed by various scholars and philosophers.

 

1.   Malthusian Theory of Population growth.

 

Thomas Robert Malthus (1766-1834 was the first economist to propose a systematic theory of population. He articulated his views regarding population in his famous book, Essay on the Principle of Population (1798), for which he collected empirical data to support his theory. His expression on population was a landmark in the history of population theories, where he generalized the relationship among population factors and social change.

 

Malthus proposes the principle that human populations grow exponentially (i.e., doubling with each cycle) while food production grows at an arithmetic rate (i.e. by the repeated addition of a uniform increment in each uniform interval of time) in Essay on the Principle of Population. Thus, while food output was likely to increase in a series of twenty-five year intervals in the arithmetic progression 1, 2, 3, 4, 5, 6, 7, 8, 9, and so on, population was capable of increasing in the geometric progression 1, 2, 4, 8, 16, 32, 64, 128, 256, and so forth. This scenario of arithmetic food growth with simultaneous geometric human population growth predicted a future when humans would have no resources to survive on. Malthus urged controls on population growth to avoid such a catastrophe,

 

On the basis of a hypothetical world population scenario which was of one billion in the early nineteenth century along with an adequate means of subsistence at that time, Malthus proposed that there was a potential for a population to increase to 256 billion within 200 years whereas the means of subsistence were only capable of being increased enough for nine billion to be fed at the level prevailing at the beginning of the period. He therefore considered that the population increase should be kept down to the level at which it could be supported by the operation of various checks on population growth, which he categorized as “preventive” and “positive” checks.

 

1.1. Preventive Checks

 

Preventive checks exercise their influence on the growth of population by bringing down the birth rate. Preventive checks are those checks which are applied by man. Preventive checks arise from man’s fore-sight which enables him to see distant consequences He sees the distress which frequently visits those who have large families.

 

He thinks that with a large number of children, the standard of living of the family is bound to be lowered. He may think that if he has to support a large family, he will have to subject himself to greater hardships and more strenuous labour than that in his present state. He may not be able to give proper education to his children if they are more in number.

 

Further, he may not like exposing his children to poverty or charity by his inability to provide for them. These considerations may force man to limit his family. Late marriage and self-restraint during married life are the examples of preventive checks applied by man to limit the family.

 

1.2 Positive Checks

 

Positive checks are applied by nature, which exert their influence on the growth of population by increasing the death rate. There are various positive checks to population which include every cause, whether arising from vice or misery, which in any degree contributes to shorten the natural duration of human life. Insubstantial occupations, hard labour, exposure to the seasons, extreme poverty, bad nursing of children, common diseases, wars, plagues and famines ire some of the examples of positive checks. They all shorten human life and increase the death rate.

 

Malthus recommended the use of preventive checks if mankind was to escape from the impending misery. If preventive checks were not effectively used, positive checks like diseases, wars and famines would come into operation. As a result, the population would be reduced to the level which can be sustained by the available quantity of food supply.

 

1.3 The theory propounded by Malthus can be summed up in the following propositions:

(1)  Population is necessarily limited by the means of subsistence (i.e., food).

(2)  Population increases faster than food production.

(3) Population always increases when the means of subsistence increase, unless prevented by some powerful checks.

(4)  There are two types of checks which can keep population on a level with the means of subsistence. They are the preventive and a positive check.

 

The first proposition is that the population of a country is limited by the means of subsistence. In other words, the size of population is determined by the availability of food. The greater the food production, the greater the size of the population which can be sustained. The check of deaths caused by want of food and poverty would limit the maximum possible population.

 

The  second  proposition  states  that  the  growth  of  population  will  out-run  the  increase  in  food production. Malthus thought that man’s sexual urge to bear offspring knows no bounds. He seemed to think that there was no limit to the fertility of man. But the power of land to produce food is limited. Malthus thought that the law of diminishing returns operated in the field of agriculture and that the operation of this law prevented food production from increasing in proportion to labour and capital invested in land.

 

According to the third proposition, as the food supply in a country increases, the people will produce more children and would have larger families. This would increase the demand for food and food per person will again diminish. Therefore, according to Malthus, the standard of living of the people cannot rise permanently. As regards the fourth proposition, Malthus pointed out that there were two possible checks which could limit’ the growth of population: (a) Preventive checks, and (b) Positive checks.

 

1.4 Criticism of Malthusian Theory:

The theory proposed by Malthus has been a subject of keen controversy. It was criticized on the following grounds:

 

(i)  It is pointed out that Malthus’s pessimistic conclusions have not been borne out by the history of Western European countries. Population has not increased as rapidly as predicted by Malthus; on the other hand, production has increased tremendously because of the rapid advances in technology. As a result, living standards of the people have risen instead of falling as was predicted by Malthus.

 

(ii)  It was Malthus asserted that food production would not keep pace with population growth owing to the operation of the law of diminishing returns in agriculture. But by making rapid advances in technology and accumulating capital in larger quantity, advanced countries have been able to postpone the stage of diminishing returns. By making use of fertilizers, pesticide better seeds, tractors and other agricultural machinery, they have been able to increase their production greatly. In fact, in most of the advanced countries the rate of increase of food production has been much greater than the rate of population growth.

 

(iii) Malthus compared the population growth with the increase in food production alone. He should have considered all types of production in considering the question of optimum size of population.

 

(iv)  Malthus held that, living standards of the people cannot rise in the long run above the level of minimum subsistence. But living standards of the people in the Western world have risen greatly and stand much above the minimum subsistence level.There is no evidence of birth-rate rising with the increases in the standard of living. Instead, there is evidence that birth-rates fall as the economy grows. People now began to care more for maintaining a higher standard of living rather than for bearing more children. The wide use of contraceptives in the Western world brought down the birth rates. This change in the attitude towards children and the wide use of contraceptives in the Western world has falsified Malthusian doctrine.

 

(v)  There was no proof of his assertion that population increased exactly in geometric progression and food production increased exactly in arithmetic progression. It has been rightly pointed out that population and food supply does not change in accordance with these mathematical series. Growth of population and food supply cannot be expected to show the precision or accuracy of such series.

 

2.  Thomas Doubleday’s Diet Theory

Thomas Doubleday, a social philosopher and an English economist, expressed his views on various natural laws which govern population. According to him, population increase will be less when the quantity of food supply is greater.

 

2.1 Doubleday divides society into three groups:

 

(1)   The first group includes those who are in a state of affluence and are well supplied with luxuries. Their number is on constant decrease. While the number of those who are engaged in mental or physical activities and are living busy life, is on the increase.

 

(2)   The second group consists of the poor people who have less supply of food. Their number is increasing rapidly. In other words, the constant increase in population is found in the group where people are worst supplied with food. This happens in all societies.

 

(3)  The third group has those people who form the mean and median between two opposite states and who fall under the average income group and those who are tolerably well supplied with good food or who get a normal diet and do not overwork and yet are not idle. Their number is stationary.

 

Doubleday is also of the view that, “The rich produce less children as the fertility would be less amongst them and therefore, the transfer of their wealth will be distributed among a few people. Over a period of time, it may happen that there is no one as an heir to that property and therefore this wealth will pass to the children of the poor. Again when the children become rich, they will restrict their families and their wealth will be gained once again by the poor. Thus socialism comes on its own through the automatic distribution of wealth by nature.”

 

3.    Jouse De Castro’s Protein Consumption Theory:

 

Castro accepted the findings of R.J. Solankar who conducted experiments on rats in 1920. In these experiments Solankar found that with the increase in protein consumption in diet, the fecundity will decrease and it will increase with low protein content in diet. His experiment led to the following conclusions:

(i)   When 10 per cent protein was given to a female rat, per mated female rat gave 23.3 births;

(ii)  When 18 percent protein was given to each female rat, per mated female rat gave 17.4 births.

(iii) When the quantity of protein was increased to a level of 22 percent to each female rat, the birth per mated female rat reduced to 13.8 births.

 

Through these experiments Castro came to the conclusion that the fatness is affected by the consumption of protein, it increases with the protein rich diet, which leads to lower fertility. Moreover this concept of Castro is similar to the Doubleday’s diet theory that the food supply influences the rate of population increase. According to Castro, people or societies are blamed for the high birth rate in the poor countries, which is not proper. For this the people of affluent societies should be blamed, as no steps to improve the standard of living of their people nor have they made attempts to provide good food and provision of good food was made by imperial or colonial powers. Such a vicious cycle of consumption of imbalanced food, less protein intake, leading to the increase in the capacity to produce more children goes on. Castro reflected on the issue with reference to India that out of the total number of children born in India; almost fifty percent suffer from starvation and die before they reach the age of marriage. On the basis of data for different countries relating to the association of fertility with consumption of protein, Castro concluded that in 1952 two-third of the world population experienced chronic hunger, i.e., malnutrition, disease or early death.

 

He also pointed out that to eradicate chronic hunger; priority should be given to the problem of balanced food. Efforts should be made to bring more lands under the plough with improved farming methods and extensive cultivation. This is only possible through economic development leading to rising income of the poor which increases their protein consumption.

 

4.  Michael Thomas Sadler’s Destiny Theory:

 

Michael Thomas Sadler, an Economist and a British social reformer, was born in 1780. He was a contemporary of Malthus. He expressed his ideas about population in his book The Law of Population. According to Sadler, the law which regulates the growth of animals and plants is primarily the same as the law which regulates the growth of human population.

 

He was of the opinion that “The fecundity of human beings is in the inverse ratio of the condensation of their numbers.”Moreover, the fertility rate decreases with the increase in the density of population. In the agriculture based or pastoral countries where the density of population is low, the fertility rate of the population becomes high. In such countries, people have the capacity to work hard and hardworking people give birth to more children.

 

Sadler did not accept Malthus’s view that population increases in geometrical progression and food supply increases in arithmetical progression. According to him, such increase of population and food supply in mathematical terms just cannot happen, because when population increases density too will increase. He did not accept the fear of Malthus that positive checks by nature take place with the growth of population. He also did not believe in the preventive measures of birth control described by Malthus.

 

He said people will be able to produce food according to their needs if the fertility rate of population increases, hence populations will adjust themselves according to their needs. Sadler believed that increase in population density will increases the unhealthy atmosphere which leads to the increase in the death rate. Further, Birth rate will be increased due to the increased death rate, whereas if the death rate is low, the birth rate also goes down to compensate population loss.

 

5.  Herbert Spencer’s Biological Theory:

 

Herbert Spencer, a famous English philosopher and sociologist, propounded the biological theory of population in his book The Principles of Biology. Spencer argued that fecundity decreases if complexity of life increases. According to him, natural change in the reproductive capacity of human beings leads to the changes in the growth of population. Therefore, his theory has been known as a natural theory of population which is similar to the theory of Sadler and Doubleday.

 

Spencer believed that “there exists antagonism between individuation (survival) and genesis (reproduction)”. When an individual at his work place does hard work for his personal development, the desire for reproduction decreases. This is noted from the fact that fertility is more among rural individuals where life is simple, whereas fertility is low in an industrial society where life is more complex, more educational pressure and the brains are overtaxing.

 

According to Spencer we have four different situations which explain the relation between individuation and genesis:

(i)  The individuation will automatically below when there is high genesis. This situation we find among the poor.

(ii)  The genesis will be low when there is high individuation. Such a situation we find among the rich.

(iii) The individuation will improve when the genesis is low.

(iv) The genesis will be high when the individuation is low. In poor people, we find less individuation and more genesis.

    According to him, people can be divided in three groups:

(i)  Poor people who live a simple life whose fertility is high;

(ii)  Middle class people whose fertility is correspondingly low;

(iii)  People who live developed or complex life whose fertility is fairly low.

 

According to Spencer, in societies where people, especially woman, are educated and belong to rich families, their reproductive power is low, as compared to the poor who are uneducated and whose reproductive power is high.

 

6. Corrado Ginnis’s Biological Population Theory:

 

Corrado Ginnis, a sociologist, was born in Italy in 1884. According to Ginni, fertility will be very high in a nation when it is in the primary stage. Due to high fertility, social and economic problems become complex. Further, the problems of trade and industry also become more complex. At this time, fertility starts declining. “He thought that the evolution of a nation or any society was closely linked to the changes in their rates of population growth and to the varying propositions of this growth coming from the different social classes.”

 

Ginni was of the opinion that only biological factors are responsible for the increase in population and therefore his theory of population can be characterized as a natural law theory. He was of the view that social and economic factors can influence the population growth but the reasons for the increase or the decrease in population growth are only biological. Thus this theory is based on biological aspects.

 

Ginni believed that the population growth is similar to the cyclical growth of an individual. In the first stage, the growth of population is very rapid while in the second stage, the growth is comparatively slow. In the third stage which is known as senescence, population decreases and there is deterioration in the quality of civilization. According to Ginni, first the fertility rate declines among the rich. After that when the energetic and prolific poor people enter the rich class, their fertility also decreases. When the whole society or country becomes rich, there is decline in population growth due to the weakening of the reproductive instinct.

 

7.  Dumont’s Theory of Social Capillarity:

 

Arsene Dumont (1849-1902) has propounded the Theory of Social Capillarity. Dumont studied the growth of population in France in the later part of nineteenth century and found that the reason for low fertility in France was high intellectual and aesthetic development.

 

In the words of Dumont, “The development of number in a nation is in inverse ratio to the development of individual.”According to him, “The direct cause of decline in birth rate was the movement of individual from the lower to the upper class. The individual tends to rise to higher levels in his social environment by process similar to physical capillarity.” Further, “what gravity is to the physical world, capillarity is to the social order.”

 

According to Dumont, there are three principles of population that are related to the stages of social development:

  1. In the preventive stage, the Malthusian theory of population applies where human beings live like animals. On what they can find, they increase in geometrical progression.
  2. In the intermediate stage, “Population proportions itself automatically.” In such a society, population increases as food supply increases because population can produce food itself. Here positive checks do not become necessary.
  3. In a modern civilized society, Dumont applies his social capillarity principle. In such a society, every individual wants to achieve higher economic and social status. For this, a small family is imperative, because one cannot climb high on the social ladder with the burden of more no of kids in the family.

   When an individual earns more income and wealth, his ambition for better position and higher social prestige goes up and consequently the number of children decreases. Therefore, in a civilized society due to social capillarity, fertility goes down, it also decreases when people migrate to cities from rural or backward areas.

 

8.  Karl Marx’s Theory of Surplus Population

 

Karl Marx, the famous author of Das Kapital, did not propound any specific theory of populations. However, he rejected the Malthusian theory as completely imaginary and false. He did not accept Malthus’s view that population increases in geometrical progression and means of subsistence in arithmetical progression. Marx’s views about population growth are based on his theory of surplus value. According to him, the problem of population arises only in a capitalist society which fails to provide jobs to all workers because the supply of labour is more than its demand. As a result, there is surplus population. But there is no surplus population in a socialist society where the means of production are in the hands of workers. All able bodied workers are employed and there is no surplus labour. So there is no need to check the growth of population in a socialist country.

 

Capitalism, according to Marx, is divided into two classes – the workers who sell their ‘labour-power’, and the capitalist who own the ‘means of production’ (factories). Labour-power is like any other commodity. The labourer sells his labour for its value. And its value, like the value of any other commodity is the amount of labour that is required to produce labour-power. In other words, the value of labour-power is the value of the means of subsistence (i.e., food, clothing, housing, etc.) necessary for the maintenance of the labourer.

 

This is determined by the number of hours necessary for its production. But the value of commodities necessary for the subsistence of the labourer is never equal to the value of the produce that labourer produces. If a labourer works for ten hours a day, but it takes him six hours’ labour to produce goods to cover his subsistence, he will be paid wages equal to 6 hours’ labour. The difference worth 4 hours’ labour goes into the capitalist pocket in the form of profit. Marx calls this unpaid work “surplus value”. According to Marx, this surplus value leads to capital accumulation. The capitalist’s main aim is to increase the surplus value in order to increase his profit. He does so by “the speeding up of labour”, which means increasing the productivity of labour.

 

When the productivity of labour increases, the labourer produces the same commodity in less hours, say 4 hours, or he produces more (two) commodities, say in 6 hours. This raises the surplus value and hence the capitalist’s profit. The increase in the productivity of labour requires a technological change that helps in increasing total output and lowering the cost of production. He introduces labour-saving machines which increase labour productivity. This process of replacing labour by machines creates an industrial reserve army which increases as capitalism develops. The industrial reserve army is the surplus population. The larger the industrial reserve army, the larger the surplus population and the worse are the conditions of the employed labourers.

 

This is because the capitalists can dismiss dissatisfied and troublesome workers and replace them from the ranks of the reserve army. Capitalists are also able to cut down wages to a semi-starvation level and raise more surplus value, while the surplus population increases. Marx explains his surplus theory of population thus:

 

“It is the working population which, while effecting the accumulation of capital also produces the means whereby it is itself rendered relatively superfluous, is turned into a relatively surplus population, and it does so to an ever increasing extent. This is a law of population peculiar to the capitalist method.”

 

9.  Leibenstein’s Motivational Theory of Population Growth

 

Leibenstein’s theory of population growth is based on his empirical evidence that the rate of population growth is a function of the level of per capita income which, in turn, depends on the stage of economic development. It is based on Dumont’s “Social-capillarity Thesis” which states that with the increase in per capita income, the desire to have more children as productive agents declines.

 

This means that fertility rate declines with economic development as per capita income also rises. Similarly, improvement in public health measures with economic development reduces the mortality rates. But the decline in the mortality rate is fast as compared to the decline in the fertility rate. This creates a “fertility gap” which continues to widen for quite some time.

 

Leibenstein explains the fertility gap in terms of the cost-benefit analysis of bringing up an additional child. There are three types of benefits or utilities which parents derive from an additional child.

They are:

(a) Consumption utility which they get out of love and pleasure by rearing a child.

(b) Productive utility when the child starts earning from childhood and is a source of income for his parents.

(c) Old age security utility which the child possesses when he supports his parents in old age who are unable to earn.

 

The costs of bringing up an additional child are of two types – direct and indirect. The direct costs relate to expenditure on feeding, clothing, education, etc. These expenses are incurred by parents till the child starts earning and become self-supporting. The indirect costs relate to the opportunities foregone by parents when an additional child is born. Such opportunities foregone are earnings lost by the mother during and after the pregnancy, less social and spatial mobility of parents due to additional responsibility in bringing up the additional child, etc.

 

Lack of spatial mobility means potential loss of income. On the whole, the cost of bringing up an additional child is less to parents with low per capita income and high with high per capita income. There are three types of effects which influence the utilities and costs of bringing up an additional child during the process of economic development. They are the income, survival and occupational distribution effects. With economic development, as per capita income increases, the chances of survival increase and there are changes in the occupational distribution.

 

The motivational theory, as explained above, is closely related to the different stages of economic development. To start with, at the subsistence equilibrium level of income, fertility and mortality rates are the maximum consistent with the survival rate of population. If the per capita income is raised above the subsistence equilibrium position, the mortality rate falls without any drop in the fertility rate. The result is an increase in the growth rate of population.

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References

  • Ehrlich, I., & Lui, F. (1997). The problem of population and growth: a review of the literature from Malthus to contemporary models of endogenous population and endogenous growth. Journal of Economic Dynamics and Control, 21(1), 205-242.
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  • Malthus T.R. 1826. An Essay on the Principle of Population, Sixth Edition, App.I.6
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