Article on Age Composition of Population
Age is an important factor which determines the physical as well mental capacity of people to engage themselves in an economic and other activities. It is one of the important demographic attributes of a social group which plays very important role in migration, population growth and the structure of population. The age structure influences the economic and social interactions, social attitudes and social and occupational mobility. Children upto the age of 14 years are considered as too tender to bear any physical and mental burden. Being immature, they can not be entrusted with responsible jobs. Like wise, the persons above 60 years become too weak to undergo physical strain because of their old age and feeble health. They want to retire and live peacefully for the remaining period of life.
●Determinants of Age Composition:-
There are three fundamental determinants of age composition of population: fertility (natality), mortality and mobility (migration). These three determinants of age composition (structure) are inter related and inter-dependent and any change in one of these may affect the other two. Through these variables the socio-economic conditions of a community definitely influence the age structure of concerned population.
(1) Fertility:
The fertility rate (birth rate) determines the proportion of population (structure of population) in different age groups. In the developing countries of Asia, Africa and Latin America, which are characterised by high fertility or birth rates have large proportions (30 to 40 percent) in young age groups (0-14 years). In these countries, longevity of life (life expectancy) is short and consequently, the proportion of population in the old age groups (65+) is also not very large (below 5 per cent).
In contrast, the developed countries of Europe, Anglo-America, Australia, New Zealand and Japan with low fertility rates and with long expectancy of life have below 25 percent of their populations in the young age-groups (0-14 years). The proportion of population in the older age groups is relatively large (above 10 per cent). It is noteworthy that most of the developed countries of the world have completed their demographic transition and possess age structure where the proportion of younger population is low and that of old people is high. In these countries decreasing trend in fertility contributes to the increase in the proportion in older ages.
(2) Mortality:
Mortality or death rate is also an important determinant of age-structure of a population. High death rate adversely affect the proportion of population in a particular age group. Generally, when the death rate decreases in younger age groups, the proportion of children will tend to rise and that of the older population will tend to fall, When it decreases in older age-groups, the proportion of older people will rise but that of children will tend to fall. When the death rate is low both among younger and older age groups (as in developed countries) it contributes to an increase in the proportion of population in the older age groups, In many developing countries of the world, the In decline in mortality is sharper in childhood than in the older age groups which has resulted in the swelling up (increase) of numbers in younger age groups (0-14).
(3) Migration:
Migration is also an important determinant of age-structure of population but its impact on the age structure is quite different from that of fertility and mortality as the migrants have their own specific age pattern and natural increase pattern. Generally, the migration of population tends to be age-selective, hence the impact of migration upon age-structure may be seen in both communities-from where they migrate and to where they reach. "As the migrants tend to be relatively younger and possessing high rate of natural increase, their usual short-term impact is the decline in the proportion of older adults and aged population. This youthful effect continues if the volume of migration is maintained. The youthful effect will tend to decline, however, if the volume of immigrants tapers off or the new migrants happen to be of older ages".
●Methods of Analysis of Age Structure:-
In the analysis of age composition of population, three different methods have been commonly used by the geographers, demographers and other social scientists. These methods are (A) Age Groups, (B) Age Pyramids, and (C) Age Indices.(A) Age Groups:-
This is a most common method used for the analysis of age distribution of population by geographers because it permits regional comparisons with the help of choropleth maps.
According to continuous and discrete series and class-intervals adopted the age groups may be determined variously:
(2) 0-10, 11-20, 21-30, 31-40, 41-50, 51-60, 61-70 etc.
(3) 0-14, 15-35, 36-59, 60 and above.
Generally, 15 years and 60 or 65 years are taken as break point or divide and on this basis population is classified into three broad groups:
(1) Young age group (0-14),
(2) Adult age group (15-59 or 65) and
(3) Old age group (60 or 65 and above).
(i) Young Age Group: The young age group includes children below 15 years of age. Children upto the age of 15 years are considered as too tender to bear any physical and mental burden. Being immature, they can not be entrusted with responsible economic activities. The proportion of young age group in total population of a country is considerably influenced by the stage of demographic transition through which it is passing. Its proportion is large in the first and second stage of demographic transition in which birth rate is very high, Table 8.5 reveals that on average, in the total population of the world, about 26 percent population is of children below the age of 15 years. The corresponding figure for developed countries comes to be only 16 percent while for developing countries and least developed countries these figures are as high as 28 percent and 40 percent respectively.
(ii) Adult Age Group: The adult age-group comprises of population coming in the age group of 15 to 65 years. For developing countries like India, with low life expectancy, the upper limit is sometimes lowered to 60 years, "The adult age group is biologically the most reproductive, economically the most productive and demographically the most mobile." (Trewartha, 1969, 122).
There are not very much regional variations' in the proportion of adults. On average, about 66 percent population of the world comes under this age group. This proportion for developed and developing countries are 66 and 65 percent respectively while in least developed countries, proportion of adult population comes to be 56 percent. The adults are found physically and mentally suitable for their engagement in various economic activities. As such the persons of this age group are regarded as 'active population' or 'effective population'. Though all the persons of adult age group are not available for work because of various unfavourable factors such as defective physique, health, economic conditions, education and training, sex etc., but major portion of the working population comes from the active age-group (15-64 years). The adult age group is sometimes divided into two sub groups: (1) Youths (16-34) and (2) Mature adults (35-64).
(iii) Old Age Group: All those people who have attained the age of 65 and above are included under this age group. The persons of this age group are designated as senior citizens or elders, The proportion of population in this age group is governed largely by death rates. Since the female mortality rate is lower than males in all ages, they tend to outnumber the males in this age group. The proportion of old age group in total population tends to improve with the growing stages of demographic transition.
About 9 per cent population of the world as a whole is found under old age group. Its proportion in the population of developed countries comes to be as high as 18 percent. In contrast only 7 percent and 4 percent population of developing and least developed countries is found under old age group. People in this age group, particularly females are biologically non-reproductive and economically most non-productive.
(B) Age Pyramids:-
Age pyramid is one of the popularly used methods of analysing age composition of a population. Age pyramid is also known as 'age and sex pyramid'. In this method, data relating to different age-groups separately for males and females are plotted to construct a diagram called pyramid diagram because it has the shape of a pyramid. In the construction of this diagram, successive age groups starting from zero are showed along the vertical axis at a regular interval such as 5 or 10, and ending according to the age structure of population under study. The pyramid is divided vertically into two parts, in which right side represents female population and the left side represents the male population. Usually the percentage of males and females in each successive age group is represented, sometimes the absolute numbers of males and females are also represented. In this diagram, usually the number of males and females in each successive age-groups is less than that in the preceding age-group. Thus, the representation of age and sex composition combinedly gives it the shape of a pyramid.
The shape of pyramid diagram varies considerably from one country to another depending mostly on the stage of the demographic transition through which the country is passing. The countries which are in the first stage of demographic transition have very broad base which narrowed upward rapidly presenting a concave shape to the sides of the triangle. The developing countries which are at the second (rapidly increasing population) stage of demographic transition show large base of the pyramid mainly due to high birth rate and sharply declining death rate. The developed countries which are at the third (stationary) stage of the demographic transition represent a narrower base with about equally wide successive age groups tappering off gradually.
The shape of the pyramid may also be significantly modified by a number of factors such as wars, epidemics, migrations, baby booms etc. which cause large scale abnormal deaths and make distortions in the normal shape of the pyramid. Sometimes the distortion in age pyramid is the product of more than any single factor, so that it becomes difficult to clarify the role of each factor in forming a typical shape to a age pyramid.
(C) Age Indices:-
The age composition of population may also be analysed with the help of age indices The calculation and use of age indices for analysing the age distribution is not very common. The calculations of different age indices are based on the proportion of population in three broad age-groups: youngs, adults and olds. According to the aim of the study following types of age indices may be used:
(i) Ratio of youngs and adults,
(ii) Ratio of youngs and olds,
(iii) Ratio of adults and olds,
(iv) Ratio of youngs and adults + olds,
(v) Ratio of olds and youngs + adults,
(vi) Ratio of adults and youngs + olds.
Dependency Ratio: The sixth index mentioned above presents the ratio of adults: youngs + olds and is very helpful in the analysis of an economy. Generally, the adult population is considered as active (working) population while children below 15 years and old persons of 65 years and above are dependent on active population, Following is the formula for the calculation of dependency ratio:
Dependency ratio = young + old population
----------------------------------- x 100
adult population
Thus, the dependency ratio presents an index of non working: working population in percent The dependency ratio is generally high in the case of developing and least developed countries of the world mainly due to large number of young populations Different age indices also can be represented graphically on the map which may help in the analysis of spatial variations in these indices.
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