Factors that influence the size of population
- Crude birth rate:- This is the number of births per annum per thousands of population. This birth rate only records live birth but does not take into account the infant mortality.
- The crude death rate:-This is the number of people that die in a country per thousand of the population. It is crude because it does not take into account the age of the person at death. If this rate is low then the population size is likely to be big and vice versa assuming other factors are constant.
- Net Reproduction Rate (NRR):- This measure the number of daughters a new born girl would bear during her life time after making assumption about fertility and expectation of life. The NRR therefore measures the extent which a given collection of new-born girls will reproduce themselves. Thus If the NRR "is one, it indicates that fertility rate in society is at replacement rate, If the NRR is high, the population size will be big and vice versa.
- Population momentum: This refers "to the tendency for the population to continue growing. even when there is a decline in the birth rate. This can be as a result of a high population of women of child bearing age in the population such a ratio brings about an increase in the population size.
- Infant mortality rate:- This records the number of deaths of children below the age of 12 months expressed as number per thousands of children in this age group per annum. If this is low, the population size will be big and vice versa.
- Fertility rate:- This measures the average number of children born per woman of child bearing years i.e. age from 15-45 years that would result if women survived to the end of their reproductive age. If this is high, then the population size would be high and vice versa.
- The marriage partners-Given that the majority of births are to married women, the number of marriages directly affects the population size. Besides, the age at which people marry also influences the population size. If the girls marry at a younger age, the population size is likely to be high and vice versa.
- Size of the families:- When the population has preference for big family sizes, the population size is likely to be big and vice versa.
- The migration pattern:- If immigration exceeds emigration then the population size will increase and vice versa.