Understanding Population Dynamics: Birth and Death Rates

Posted on Feb 4, 2025 in Geography

The natural movement of population refers to changes in the number of inhabitants due to birth and death rates. The difference between these two rates is known as vegetative growth. It is positive if the birth rate exceeds the mortality rate and negative if the reverse is true.

The number of births and deaths is not expressed in absolute terms but in relation to the number of inhabitants. Therefore, we use birth rates and death rates, both expressed in parts per thousand (‰).

  • Birth Rate (BR) = (Number of births in a year ÷ Total population) x 1000
  • Mortality Rate (MR) = (Number of deaths in a year ÷ Total population) x 1000

Birth Rate

The world average birth rate is 28‰. In developed countries, it falls below average (usually less than 15‰), while in developing countries, it is around the average. In underdeveloped countries, it is significantly higher (typically between 40‰ and 60‰).

Closely related to the birth rate is the fertility rate, which is calculated as follows:

Fertility Rate (FR) = (Number of live births in a year ÷ Number of women of childbearing age (15-49 years)) x 1000

For a population to grow, a fertility rate of at least 2.1 is necessary to ensure generational replacement. Generally, developed countries have a fertility rate of around 1.6‰, while underdeveloped countries have a rate of around 3.3‰. However, there are extremes in both cases. For example, Spain has one of the lowest rates in the world at 1.2, while Niger has one of the highest at 7.4, and Saudi Arabia at 6.4.

In summary, underdeveloped countries experience significant population growth (although it is declining: the current rate of 3.3 was 6.2 in 1950), while developed countries often do not reach the necessary fertility rate for generational replacement.

Factors Affecting Birth Rate

The following factors influence the birth rate:

  1. Biological Factors: These include the proportion of young women in the population and the overall health and nutritional conditions. Improved conditions generally lead to lower infant mortality and fewer children per family.
  2. Social Factors: The emancipation of women and economic conditions play a significant role. Developed countries tend to have fewer children due to the economic burden involved, while underdeveloped countries may have more children to contribute to family income.

Mortality Rate

Mortality Rate (MR) = (Number of deaths in a year ÷ Total population) x 1000

The mortality rate is a less clear indicator than the birth rate, as it is affected by the aging population in some countries. In general:

  • Virtually all of America has a mortality rate of less than 10‰.
  • Mediterranean Europe has a mortality rate of less than 10‰.
  • Central and Northern Europe have mortality rates between 10‰ and 20‰.
  • Asia has mortality rates between 10‰ and 20‰, although some countries have rates as high as 30‰.
  • Africa has mortality rates between 10‰ and 30‰, with some countries exceeding 30‰.

Therefore, it is necessary to supplement this data with other rates:

Infant Mortality Rate

Infant Mortality Rate (IMR) = (Number of deaths under 1 year of age ÷ Number of live births in that year) x 1000

  • Developed countries: less than 20‰
  • Developing countries: between 20‰ and 80‰
  • Underdeveloped countries: between 80‰ and 140‰

Life Expectancy

Life expectancy is the average number of years a population is expected to live.

  • Developed countries: More than 70 years. Japan has the highest life expectancy in the world (80 years), followed by Spain (78 years). On average, life expectancy in these countries is 7 years higher for women than for men.
  • Developing countries: 60 to 70 years.
  • Underdeveloped countries: Less than 50 years, with the majority of African countries having a life expectancy below 40 years.

Factors Affecting Mortality

  • Biological Factors: Aging population and endemic diseases.
  • Social Factors: Increased mortality in urban areas, economic and cultural factors, and state spending on health. For example, Sweden spends $500 per person per year on healthcare, while Ethiopia spends $1 per person per year.