Some economists have put forward the optimum Theory of population to replace the Malthusian Theory. Prof. Sigdwick gave the basic idea of optimum population in his book ‘principles of Political Economy’. It was further developed by Prof. Cannon and refined and polished by Prof. Robbins, Dalton and Carr Saunders.

 

Optimum Population

 

Number alone does not show whether or not a country is under or over populated. A particular density of population per square mile might be too large for one country but not for another. The production of a commodity requires the employment of a number of factors of production, of which labour is only one. These have to be combined in a certain proportion in order to obtain the maximum output. Hence, according to J.L. Hanson “The amount of labour which, combined with the other factors of production, yields the maximum output is the optimum population for that particular country”.

 

Expressed in other way optimum population means the ideal number of population that a country should have considering its resources. When a country’s population is neither too big nor too small but just that much which the country has, it is called optimum population. Hence, the optimum population can be defined as the one on which output per capita is highest. ‘According to R.G.Lipsey and C.I-Iarbury, “The optimum population is one that maximizes per capita national income.” What is the optimum population for any country depends on its natural resources and its stock of capital.

 

Under Population

 

When population is below optimum, it is the case of under population. In other words, if the population of a .country falls short of the optimum it can then be considered to be under-populated. The number of people is insufficient for the fuller utilization of natural and capital resources. Under such situation, the increase in population will lead to increase in output per capita. Because. The increase in population increases labour force. The division of labour will be possible. There will be fuller utilization of natural and capital resources. The market for product will increase. Finally the point is reached at which the output per capita is the highest.

 

Over Population

 

If the population of a country exceeds the optimum it is clearly Thus country poor in natural resources and lacking capital might be economically over-populated, although in terms of numbers its population is small. The resources will be insufficient to provide employment to all. The output per capita will diminish, standard of living will fall, malnutrition and disease will engulf the people.

 

The table below illustrates the optimum theory of population.

 

Population (In Crore)	Per Capita Income (In Rupees)	Size of Population
1	2000	Under-population
2	3000
3	4000	Optimum-population
4	3000
5	2000	Over-population

 

 

The table shows that in the beginning when population increases from 1 crore to 2 crore, per capita income also increases. This is the case of under-population when the population of the country is insufficient to exploit all the resources available in the country. When populating is 3 crore per capita incomes is highest. But when population exceeds 3 crore and increases to 4 and 5 crore per capita income begins to decrease. This is the case of over-population when the resources are insufficient to provide employment to all. So, the population of 3 crore is the optimum population. When the per capita income or output per capita is highest.

 

It is thus evident that the situation of both under and overpopulation are bad. The concepts of optimum population, under population and over-population are represented in the figure below:

 

 

 

In the figure, OX axis represents size of population and OY axis represents national income. MP is the marginal product curve. In the beginning as the nation’s population increases, each new citizen adds more to total output than did each previous citizen. Thus the marginal contribution to national income of additional citizens increases. As the population goes on increasing, however, all of the opportunities for improving the division of labour and for exploiting scale economies will eventually be exhausted. So, further new inhabitants will add less to total production than did each previous addition to population. Now the marginal product of further additions to population will fall. In figure falling marginal product sets in after the population has reached N1.

 

AP is the pen capita output curve or average product curve. The AP curve first slopes upward, reaches maximum and then slopes downwards. It means that in the beginning, as the population increases. Output per capita increases till N2 are reached. Eventually, the falling marginal product of new inhabitants will cause a fall in the average product of all the population. In the figure the average product per person begins to fall when the population reaches N2. The population that maximizes output per person is N2.

 

At N2 level of population, output per capita is highest and is equal to N2 F. F is the maximum point. Therefore N2 is the optimum population. If the population of a country is less than N2, it is under populated and if more than N2, it is over-populated. If the population increases beyond N2, output per capita begins to decline.

 

Change in Optimum Population

 

The optimum population, however, is not fixed, for over a period of time. Conditions are liable to change. What was formerly the optimum may cease to be so under changed condition of production. If it were possible to increase the supply of other factors proportionately to increase in population, the optimum might be raised. Optimum population is relative to resources and technology. So if there is increase in capital stock or natural resources or level of technology. There will be an upward shift in the average and marginal product curves. The per capita output will increase. This means that the level of optimum population too will increase. This has been represented in figure below:

 

 

As shown in figure, with given resources and technology, the per capita output curve is AP. Here optimum population is and maximum output per capita is NF.

 

When capital and natural resource increase or there is improvement in technology, the per capita output curve shifts upward in the form AP, Now the optimum population is N, and maximum output per capita is N,F,. Here both level of optimum population and maximum output per capita is higher than before.

 

Likewise, further increase in resources and technology will shift the per capita output curve upward in the form of AP2. Now the level of optimum population and maximum per capita output are N2 and N2 F2 respectively which are higher than before.

 

Dalton has given a formula to measure the extent to which the actual population of a country deviates from the optimum population. The extent of deviation is called maladjustment.

 

Formula is

 

 

M = Maladjustment

A= Actual population

O = Optimum population

 

If M is positive, the country is over-populated and if M negative, the country is under-populated. This can be illustrated by the help of an example. Suppose that the actual population of a country is 2 crore, and its optimum population is 1.5 crore, then,

 

 

=

 

=0.3333

 

The country is over-populated to the extent of 0.3333

 

Limitations (Criticisms) of Optimum Theory

 

The Optimum Theory of population has following limitations:

 

• No Political Consideration

 

The optimum theory is based on economic consideration only. It has not taken political consideration. Population may be a blessing in disguise from political viewpoint. The more population is useful at times of war. There is no wonder that some countries are encouraging population increase basically due to political reason.

 

•  Imaginary Concept

 

The optimum population is an imaginary concept. Because, less population cannot be increased abruptly nor more population can be reduced instantly. Hence, it is difficult to achieve the optimum population.

 

•  Optimum Population is not Rigid

 

The optimum population is not a rigid one. It is flexible. The level of optimum population increases with increase in resource and technology. Likewise, it decreases with decrease in resources and technology. It is, therefore, difficult to determine what is optimum.