To explain the changes in population evolution and to analyze their development were demographic formulas or rates, such as birth rates and mortality.
The concept of birth refers to the number of births that occur in a population at any given time. To measure it, a parameter known as the crude birth rate (TBN) is used , which indicates the number of live births per thousand inhabitants in a year.
The birth rate is very different in different parts of the world. In the developed regions it is very low, however, it is much higher in the underdeveloped regions. Africa is the continent with the highest birth rate.
All these variations, both internationally and regionally, are determined by cyclical factors:
- Economic development . The more developed countries generally have birth rates below 20%, while in less developed regions there are rates of about 40%. In the more developed countries the children represent an economic burden (spending on education, medical care, food, etc.) up to high ages. In underdeveloped countries, the children work from an early age and, in addition, take care of their parents in old age.
- The culture . In Western countries, young adults tend to leave their parents’ homes later, marry later and, as a consequence, also postpone the birth of the first child, which reduces the number of people in the family group. In countries with other cultures, women often marry early, often before the age of 18. In addition, some cultures grant social prestige to the number of children and others do not.
- The social structure. The emancipation of women and their large-scale incorporation into the world of work have led to a decline in the number of children.
- Biological factors . The proportion of young people determines the birth rate: if the young are numerous, the birth rate is higher than when the elderly population predominates.
- The religion . In general, all religions favor birth.
- The political factors . Depending on the demographic situation, there are governments that practice direct birth control policies and others that promote it through social and economic incentives.
After World War II (1939-1945), there was an increase in the birth rate, a phenomenon known as the baby boom. The intense economic growth observed between 1945 and 1973 favored the increase in the number of births. However, from the 1970s onwards, this number declined abruptly.
Calculation of birth rate (TBN):
The concept of mortality refers to the number of deaths in a population. To measure it, the gross mortality rate (TBM) is used , which indicates the number of deaths per thousand inhabitants in a year.
Mortality depends on the age of the population (it is higher in the aging countries, as in many European regions) and on health and food conditions.
Until the nineteenth century, mortality was very high because of disease, hunger and frequent wars. In the nineteenth and early twentieth centuries, mortality has declined in developed countries, thanks to improvements in health (vaccines, hygiene, etc.) and food. In the second half of the twentieth century, these advances spread in underdeveloped countries, causing mortality to fall sharply.
Until the 1970s, it was relatively easy to establish a classification of countries by mortality. Rates of over 13% per annum were for underdeveloped countries, and lower for high or medium developing countries.
Currently, it is more difficult to sustain this classification. Rates continue to decline in underdeveloped countries and at the same time increase in many developed regions, where there is an increasing number of elderly population. In this context, geographers use more expressive indexes: infant mortality and life expectancy at birth.
Calculation of the crude mortality rate (TBM)
Child mortality rate
The infant mortality rate (IMR) is measured by comparing the number of children who died before completing the first year of life and those born alive during the year. It is a good indicator of the level of development and health status of a territory. In rich countries, infant mortality is low, it does not exceed 5% a year. In some African countries, however, the rate is at 100% per year.
Calculation of Infant Mortality Rate (IMR):
Vegetative growth and real growth
To know the evolution of the population, it is necessary to know the relation between births and deaths, that is, their vegetative growth.
If in a given period the number of born is higher than the number of dead, the population grows. If deaths outnumber births in one period, population declines.
When you also consider emigration and immigration, the result is real growth.
Calculation of the vegetative growth rate (TCV):
In order to more accurately assess the growth trend of a population, the concept of fertility was created.
It is the general fertility rate (GFR) that relates the number of births to the concrete possibilities of procreation, that is, the number of women of childbearing age (women aged 15-49).
Currently, the average worldwide fertility rate is 2.4 children per woman. However, African women have 5.5 children on average, while European girls do not reach 2.1 children per woman. This is the number needed to ensure generational renewal, that is, so that a territory does not decrease its population.
The cultural level of society, and especially of women, influences fertility: the higher the level of schooling, the lower the number of children.
Life expectancy at birth
Life expectancy at birth is the calculation of the average number of years a newborn can live. According to the UN, the world average was 67.2 years in 2010, but this figure hides great contrasts.
- Differences according to sex. In developed countries, the life expectancy of women is higher than that of men. On the contrary, in the underdeveloped countries, many women die young due to problems related to pregnancy and childbirth.
- The major differences according to the level of development. From 2005 to 2010, according to the UN, developed countries had a life expectancy above 79 years. In many underdeveloped countries, however, she did not reach age 49.
Life expectancy is increasing in the world, but the onset of diseases, such as AIDS, which has caused a great deal of mortality in Africa, or economic crises can cause them to regress in certain areas.