The most commonly used index of fertility is the crude birth rate (CBR). Generally, birth rates in developed countries are low, below 20%o, and in developing countries are high, being up to 40%o or even higher.
(1) Demographic structure:
The character of a population’s age-sex composition is of fundamental significance. It is to be expected that regions with a high proportion of adults wilt tend to have high birth rates.
Generally speaking, the more advanced the level of education reached, the smaller will be the average size of families. With education come knowledge of birth control, greater social awareness and a wider choice of action.
This factor may also be linked with class, since it is often the case that knowledge correlates with social standing.
Lower classes are, on an average, less educated and have larger families than the middle classes, who may be more keenly aware of material wealth and have greater financial aspirations.
Many of the world’s religions, like the Muslim and Roman Catholic, encourage large families in order to safeguard the continuance of their beliefs. Some actively oppose any form of contraception.
Thus, countries and areas within countries where these religions are dominant have considerably higher birth rates than elsewhere. Italy, the Republic of Ireland and the Latin American countries are examples in point.
In Canada, Quebec province (Catholic) had, until recently, a birth rate three times higher than neighbouring Ontario (Protestaht). Algeria (Muslim) has a birth rate 47%o. Many of these regions are also economically backward and this only exacerbates the problem.
(4) Social customs:
Concepts of marriage vary between social and cultural groups. In some places, polygamy is practiced and this adds greatly to levels of fertility.
In other places, like India where most people are Hindu, the average age for girls to marry has traditionally been only 16. They have their first child at 18 and up to nine other children in the next 25 years.
Even with the introduction of new marriage laws in India, large families are likely to follow the norm.
Certain cultures attach great importance to a male heir so that large families are common in the hope of male child or in order to ensure the survival of at least one boy.
(5) Diets and health:
The poorest and most under-nourished people of the world tend to have the highest birth rates. The reasons for this are not altogether clear, but sociologists believe a correlation exists between diet and sexual appetite.
Unfortunately, high birth rates often lead to poverty, which maintains malnutrition and thus maintains a vicious circle. It is also noticeable that countries with high levels of mortality also have high levels of fertility.
This suggests that parents in these regions deliberate have many children in order to ensure that at least some reach adulthood.
The effect of war as a natural limit to population growth has been much written about. The two World Wars, for example, resulted in the loss of over 60 million lives.
However, their importance in this respect should not be overstressed. Wars usually reduce populations for one generation only; demographic recovery sets in soon afterwards with an increase in the birth rate.
During hostilities, the men folk are away fighting and the number of births naturally falls. After the war the troops return home and the birth rate suddenly rises. Most European countries experienced such a ‘fertility bulge’ in the years 1918-1920 and again in 1946-1949.
Occasionally, birth rates even more closely linked to politics. During the 1930s, both Germany and Italy encouraged the procreation of children by offering state bounties and even medals to prolific mothers.