Measurement of Population Growth

Measurement of Population Growth

Every human population, normally, may have a change in its size over a period of time. Each change in the population size may be an increase or decrease in magnitude. Sometimes, the population size may remain without any change. Such a population is known as stable population. The tendency to increase in the population size may be called as population growth. Every government requires information about the rate of growth of its population.

If many new born babies in a population are female, the corresponding population size may increase. If gender of the infant deaths is female, change in the population size may be downward. Hence, fertility and mortality rates, individually, do not provide knowledge on population growth.

Quantitative ideas about the growth of a population can be obtained from several measurements. Among them,

(i) Crude Rate of Natural Increase, and

(ii) Pearl’s Vital Index

may be considered as the basic indicators of population growth. These two measures can be calculated using the following formulae

Crude Rate of Natural Increase = CBR – CDR

Pearl's Vital Index = [CBR/CDR] ×100

Positive values of Crude Rate of Natural Increase indicate the net increase in the population. Similarly, negative values of Crude Rate of Natural Increase indicate the net decrease in the population.

If Pearl’s Vital Index is greater than 100, then it can be regarded as the population is growing. On the other hand, if this index is less than 100, it can be regarded as the population is not growing. The above formula shows that the Vital Index can also provide knowledge on birth-death ratio of the population.

These two measures are simple and easy to calculate. They indicate whether the number of births exceeds the number of deaths. However, these two measures suffer from the limitations of CBR and CDR. They cannot be used for comparing two different populations. Also, information regarding whether the population has a tendency to increase or decrease cannot be obtained from these two measures.