POPULATION PROCESSES

Study of population processes requires separate measurements of nuptiality, fertility, mortality, migration and social mobility. Among them, nuptiality is measured in terms of the mean age of marriage and proportion married in different age groups. Fertility is measured by birth rate, total number of children ever born, and total fertility rate.

Birth rate is defined as

((Number of births in a year/total population))*1,000

If a measure of fertility is to be obtained from census or surveys, the average number of children ever born per woman may be computed for different age groups of women. Average number of children ever born among women in the age group 40-44 (sometimes 45-49) is of special significance. It is called the total fertility rate.

Likewise, mortality is measured by the death rate. Death rate is defined as

(Number of deaths in a year/total population) *1,000

Birth and death rates are called crude rates as they are dependent not only on the rapidity of reproduction and mortality but also on age and sex composition of population. In many developed countries where on an average, people live longer than in the less developed countries death rates are higher because their population consists more of old people. In less developed countries people live shorter than in the developed countries but their population consists more of young people. Therefore their death rates are lower.

The most commonly used measure of fertility is the total fertility rate. For computing it, one has to calculate the age-specific-fertility rates (ASFR) at different ages.

ASFR x = (No. of children born in a year to women aged x)/(No. of women aged x)