1. WORLD POPULATION
Currently, the world is inhabited by almost million people.
The distribution of the world’s population is not equal.

2. POPULATION DENSITY
In order to measure population distribution, we use population density: the relation between the number of inhabitants in a place and the size of area it occupies.
Population density is calculated by dividing the total number of inhabitants by the area of land occupied (in km2). The result is expressed in inhabitants/km2.
Population density =
Number of inhabitants
Area of land (in km2)

3. Population density varies from one place in the world to another:
The areas with higher population density are those with physical conditions (temperature climate, flatter land…) or human conditions (more job opportunities, stable political situation…) that make them attractive places to settle.
The areas with lower population density are those with physical conditions (very cold or very hot climate, mountainous…) or social conditions (lack of basic services such as education, health…) that make human settlement difficult. Some of these areas are demographic deserts. A demographic desert is an area with a population density of less than one inhabitant/km2.

4. NATURAL POPULATION CHANGES
Natural population change refers to increases and decreases in the population produced by biological factors (births and deaths).

5. NATALITY Natality is the number of people born over a year in a particular area.
The birth rate (BR) is calculated by dividing the number of births in an area over one year by the total population and multiplying the result by one thousand. The birth rate is expressed as a number per thousand (‰).
Less-developed countries have high birth rates because families need children to help with their economic activities. In other cases, high birth rates are a result of tradition (customs or beliefs transmitted from one generation to another). Developed countries have low birth rates. One of the reasons for this is the incorporation of women into employment outside the home.

6. MORTALITY Mortality is the number of people who die over a year in a particular area.
The death rate (DR) is calculated by dividing the number of deaths in an area over one year by the total population and multiplying the result by one thousand. The death rate is expressed as a number per thousand (‰)
Since the end of the 20th century, improvements in diet, sanitation and health care have helped to reduce the death rate throughout the world. As a result, life expectancy has increased. Life expectancy is the average number of years that a person can be expected to live according to statistics. These improvements have also influenced the fall in the infant mortality rate (IMR: ratio of the number of deaths in the first year of life to the number of live births occurring in the same population during the same period).
Less-developed countries have a high death rate because of the lack of food and health care. Developed countries have a low death rate and life expectancy is high. However, the death rate is increasing slightly in these countries, due to the ageing of the population.

7. Natural increase is the difference between the number of births and the number of deaths in a population
If the number of births is greater than the number of deaths, natural increase is positive and the population rises.
If the number of deaths is greater than the number of births, natural increase is negative and the population falls.
The rate natural increase (RNI) is calculated by subtracting the death rate from the birth rate and expressing the result as a percentage (%)
Rate of natural increase = birth rate – death rate
RNI = BR - DR
The rate of natural increase is not the same all over the world. In less-developed countries, the rate of natural increase is high, while in developed countries, it is low or even negative.