Demography is the study of human populations, their growth and decline due to changing patterns of migration, fertility and mortality and characteristics such as the sex ratio, dependency ratio, and age structure.
social demography is a field of study concerned with the analysis of how social and cultural factors are related to population characteristics. Its major focus is the impact of social and cultural factors on demographic features of society such as patterns of marriage and child bearing,the age structure of the population,life expectancy and so fourth.
Theories of demography:
Malthusian theory of population.
The malthusian theory of population is an economic approach to demography. This theory is based on two assumptions. The first assumption is that food is always necessary for mankind. The implications of this assumptions are 1)population growth is limited by the means of subsistence
2)population growth increases in a proportion to the increasing means of subsistence.
3)population growth increases in a proportion to the increasing means of subsistence unless moderated by certain checks.
The second assumption of the malthusian theory is that the passion between both the sexes will remain at the same level of intensity throughout human history. The implications of these assumptions are
1)birth rates will remain at relatively high levels
2)population growth will proceed in a geometric ratio.
The relation between these two principles will be such that while food production will grow in a arithmetic ratio(1,2,3,4),the population will grow in a geometric ratio(1,2,4,8). As a result of this relationship,the gap between population and food availability will continuously widen. The consequence is the increasing stress of rising population on the natural resources which provide sustenance. This will lead to breakdown of natural ecosystems triggering natural catastrophe.
Theory of optimum population.
the theory of optimum population is based on the following two principles.
1. the rates between total population and working population remained constant even though there is an increase in the population.
2. the availability of natural resources and capital do not change proportionate to change in population. This results in operation of law of diminishing returns.
Theory of karl Marx.
His theory of population is a critique of capitalism. The two classes which makes up a capitalist society respond differently to population growth according to marx.the rich capitalist family has low population while poor labor has more population. The population growth can be slowed down by adopting the communist system instead of letting a class revolution uprooting the capitalist system. The communist method of production would therefore solve the problem of rapid population growth.
Thomas sadler destiny and fecundity principle.
The fecundity of human beings is in inverse ratio of the conversion of their numbers.
Labor and privacy according to sadler are two important prerequisite for maintaining population growth.
Diet theory of thomas doubleday.
He drew a correlation between diet of people and population growth. He believed that man’s increase in numbers was inversely proportional to his food supply. That is the better the food supply the slower the increase in numbers.
Theory of demographic transition.
A majority of sociologist and an equal number of economists as well as demographers believe that the population dynamics in any country pass through a series of stages, each stage having its peculiarity.
First stage of demographic transition.
Death rates are high in the first stage of an agrarian economy on accounts of poor diets,primitive sanitation and absence of effective medical aid. Birth rates are also high in this stage as a consequence of widespread prevalence of illiteracy,absence of knowledge about family planning,early age of marriage and as a consequence of deep rooted social beliefs.
Second stage of demographic transition.
Rise in income levels enable the people to improve their diet. Economic development also brings about all round improvement including the improvement in transport which makes the supply of food regular. All these factors tends to reduce death rate. Thus in second stage birth rate remains high but death rate tends to decline rapidly. This accelerates the population.
Third stage of demographic transition.
One of the features of economic development is typically increasing urbanization and children are usually more of a burden than asset in an urban setting than in rural. The consiousness to maintain reasonable standard of living tends to reduce size of the family in an industrialized economy. Since the death rate is already low,this is possible only if birth rate falls. Thus the characteristics of the third stage are low birth rate,low death rate,small family size and low growth rate of population.
These three stages reveals the transformation of a primitive high birth and high death rate economy into a low birth and low death rate economy.