The logistic growth equations can predict with some degree of accuracy the density dependent population, but not the human population growth.
The very important study of human population dynamics is known as ‘demography’ and it deals with the fertility as well as mortality rates and population age composition.
The three important parameters that come under demography are:
1. Total Fertility Rate
2. Mortality Rate
3. Age Structure or Population Pyramid.
1. Total Fertility Rate (TFR)
Total fertility rate (TFR), is the average number of children that can be born alive to a woman in her life time. Averages are made because all women cannot have equal number of children; some can have more and some less.
Theoretically, when TFR = 2, each pair of parents just replaces themselves and when it exceeds 2, then there is a replacement of each generation. In developed countries, TFR value lies around 1.6, in less developed countries the value is about 3.5 and in poor countries it may be over 7.0.
Even if the replacement level fertility is achieved, population growth can continue. The continuation of population growth, despite achievement of replacement level fertility, is a phenomenon known as population momentum.
2. Mortality Rate:
An important measure of mortality is the infant mortality rate, which is the number of deaths of infants (under one year of age) per 1000 live births, in a given year.
The difference between crude birth rate (b) and crude death rate (ft) is known as the rate (r) of natural increase of population.
In developed countries the fall in birth rate is equivalent to that in the death rate. In developing countries, although the birth rate has not fallen much, there is a fall in death rate due to better health services and control of diseases.
The rapid population growth on a global scale is due to the insignificant drop in birth rate in most developing countries.
3. Age Structure or Population Pyramid:
Age structure or population pyramid is the graphical representation of data, indicating either number of people or their percentage in each age group.
An age structure diagram reflects a country’s population trends and tells about both, the recent past as well as the near future.
A stable population is one where the shape of the age structure is unchanging. When a population is both stable and unchanging in size, it is called a ‘stationary population’.
It can be concluded that age structure or population pyramid-makers are aware of the birth rates, child mortality, mortality rates and life expectancy.