Before 1750, when mortality and birth rates were balanced, the world population growth rate never exceeded 0.5%. Between 1750 and the 1930s, it did not exceed 1%. It reached a maximum of 2.1% per year, on average, between 1950 and 1970, when mortality in developing countries fell sharply, without a decline in birth rates. Subsequently, more and more developing countries saw their fertility rate decline, as it did in industrialized countries with the end of the baby boom of the 1950s. The combined effect of these two developments led to a steady decline in the world population growth rate: 1.95% in 1970, 1.26% in 2000 and 1.09% in 2020.
Another aspect of demographic dynamics that is directly related to changes in flows must be mentioned. Their very accumulation determines population stocks. Thus, the rural exodus leads to changes in the distribution between urban and rural areas, which is the process of urbanization. As for the evolution of mortality and birth rates, this is translated by the population’s age–sex distribution, conventionally represented by a pyramid. After the Second World War, developing countries experienced a large annual number of births but, due to high mortality, very few people reached adulthood. This was reflected by broad-based pyramids. In these populations, although there certainly were adults, very few were elderly people. With the gradual decline in the fertility of couples, annual birth rates decreased and the proportions of children and adults rebalanced. The population became older and demographers spoke of “aging from the bottom”. In developed countries, on the other hand, where annual birth rates are lower, the age pyramid has more adults. Over the years, these fall into the category of the third age and we speak of “top-down aging”.
These relative proportions of children, adults and the elderly led to several indicators being established, which address the issue of development. It is common to draw a distinction between consumers and producers or, more precisely, to differentiate the inactive from the active. We thus calculate a dependency ratio, where the numerator includes 0–19 year olds (young people) and those aged 60 and above (the elderly), and the denominator is the working population (20–69 year olds). Globally, the dependency ratio – equal to 75 inactive people dependent on 100 working people in 1970 – decreased to 56 in 2000 and to 53 in 2020. Another analysis was recently developed. Due to the decline in fertility, the cohorts now under the age of 15 will be replaced by smaller cohorts. But, above all, they will access the economically active ages and the relationship between consumers and producers – hitherto unfavorable due to spending on health and education weighing on national budgets – will become favorable. So far, we have provided data on world population, but is this concept actually useful?
I.2. The world population, now a useless concept?
From a demographic point of view, after the end of the Second World War, the world appeared to be divided into two major groups: developed countries and the so-called “Third World”. The former included North America, Japan, Europe, Australia and New Zealand, whereas the latter included Asia (except Japan), Africa, Latin America and the Caribbean. According to this typology, in 2020, developed countries totalled 1,273 billion inhabitants, i.e. 16.3% of the total world population of 7,794 billion inhabitants1. But this dichotomy is now outdated, at least in demographic terms, due to the growing disparities between the three continents in which developing countries are located (Table I.1 and Figure I.1).
Table I.1. Population (2020, in millions) and annual growth rate in the major groups (2015–2020 average, in %)
(source: UN DESA 2019)
| Population | % | |
| Worldwide | 7,794 | 1.09 |
| Developed countries | 1,273 | 0.26 |
| Developed countries | 6,521 | 1.26 |
| Per region: | ||
| Africa | 1,340 | 2.51 |
| Latin America | 653 | 0.94 |
| Asia | 4,641 | 0.92 |
Annual growth rates reveal that it is necessary not only to contrast the virtual stagnation of developed countries (0.26%) against the demographic dynamism of developing countries (1.26%), but also to differentiate the rapid growth in Africa from the now more moderate growth observed in Asia and Latin America.
An even more detailed analysis reveals differences within these three continents, especially in Asia and Africa. Thus, sub-Saharan Africa is growing at a rate of 2.65% per year, but this average masks deep contrasts: 1.91% in the north and 1.39% in the south, against 3.05% in Middle Africa and 2.67% in the continent’s east and west. Western and Central Asia are growing faster (1.64%) than East (0.40%) and Southern (1.20%) Asia. The differences between countries in the same region are just as remarkable (Table I.2 and Figure I.2). Size effects play a large part: highly populated countries (South Africa, India, China), often giants relative to their neighbors, weigh heavily on the averages of the sub-regions. South Africa, with its 59.3 million inhabitants (85% of the total) and a rate of 1.37%, largely determines the rate of growth in the sub-region (1.39%), whereas Botswana, which barely totals 2.3 million, is growing much faster (2.07%).
Figure I.1. Annual growth rate of major groups (2015–2020 average, in %)
(sources: Charbit (design); Opurez, IRD-Ceped (realization)). For a color version of this figure, see www.iste.co.uk/charbit/demographic.zip
Similarly, in Central and Southern Asia, India (1,380 billion with a growth rate of 1.04% per year), Pakistan (220 million and 2.05%) and Bangladesh (164 million and 1.05%) largely determine the sub-regional rate (1.20%), since these three countries on their own account for 90.9% of the sub-region’s total population. Finally, Western Asia, which includes countries with high growth rates (Iraq 2.46%, Palestine 2.38%, Yemen 2.37%), contrasts with other Asian sub-regions: 1.64% against 0.40% in East Asia, for example. This low rate is explained by China’s slow growth (0.46%), a demographic giant of 1,344 billion inhabitants, which represents 80.3% of the population in this sub-region.
What is more, the major dichotomy between developed and developing countries is questionable because, in some countries considered to be developing, fertility rates are lower than in some industrialized countries. This is the case for China (1.69 children per woman) compared to France (1.85), the United Kingdom (1.75) and the United States (1.78). From this brief statistical analysis, it is clear that, although convenient, the concept