The mecanisms of the demographic evolution
Two great factors rule the demographic evolution : fertility and mortality.
The first one, though very lowering, remains in average at a high level :
2.65 children per woman at the world scale.
In the same time, the expectation of life is lengthening. A baby who was born today
may hope to live during 65 years, in the present mortality conditions, instead of 46 years,
half a century ago. Each year, 134 billion babies were born, while 59 billion persons are dying, that is to say a positive balance of about 75 billion inhabitants.
To sum up : the world population is always in a sustained growth, but this growth
is lowering. Otherwise, thanks to the life expectancy and because of the constant lowering
of the fertility, the world population is getting old. The eldering phenomenon
has been striking the rich countries for several decades, and has reached
critical levels for some ones, but it already concerns certain South countries,
few prepared to cope with this new situation.
- Le vieillissement de la population mondiale
The South in the steps of the North
The world population begins today the last phase of a process began three centuries ago, in Europe, the process of the demographic transition. This expression means the moment
when a population passes from an "old" demographic stage, characterized by a strong
birthrate, and a strong mortality (infantile mortality, in particular) and a low growth
of the global inhabitants, toward a stage said "modern", characterized, on the contrary,
by a low birthrate, a low mortality, but with the same result, the low growth of the
The passage from the first stage to the second one occurs when the improvement
of the life conditions breaks the "old" balance.
The "demographic transition" is characterized then by a still very sustained birthrate,
but by an important fall of the mortality level, generating so the explosion of the number
of inhabitants in the considered population.
The process, begun three centuries ago in Europe, has been spreading into the South
countries, since the 50’ies. The gap of the life expectancy between South and North,
which was evaluated to 25 years in 1950 (41 and 66 years), has reduced by the half
in 2000 (63.4 and 75.8 years). The lowering of the birthrate finished by follow
the same process almost everywhere.
It has almost been divided by two, during the second half of the XXth century,
passing from 5 to 2.7 children per woman. How to explain such a rapidity ?
Even if the broadcasting of technical progress remains slow, if the developing countries
often percieve only some crumbs of it, the available technics in the South have improved :
increase of the agricultural yields, health cares, access to contraception.
The images come from Occident circulate very quickly, and impose its familial model
like an universal norm.
If Occident has spread out its demographic transition over three centuries,
the South countries, from their part, have had to manage it in half a century,
and some of them have not already finished with it. It is the case of many countries
of Africa and Asia. Globally, 620 million persons still live in a country
where the birthrate is superior to 5 children per woman.
The end of the demographic history ?
Certainly not. The after-transition has begun ; new demographic situations
are coming. One may distinguish three.
In the developing countries, the decrease has been quick, but the population keeps on rising, on account of the "demographic inertia" : the generations in age of procreate are numerous, and one has to register many more births than deaths. Aids itself won’t modify
the deal, in Africa, for example.
Another part of the world, this one rich, is living in a near-balance. It is the case
of France, the United States, the scandinavian countries, Australia. The fecondity average
is slightly inferior to the threshold of renewal of the generations, but a controlled contribution
of the immigration leads to a stabilization of the global number of inhabitants.
For a last group of industrialized countries, the fall of fecondity, recent or already
dating of several decades, has been abrupt and of a big extent, often related to major political
upheavals. This drop was enough significative to carry away more than a stabilization of the
global inhabitants, but a sensible reduction of the population.
Unless a consistent contribution of the immigration, some countries like Germany, Italy, Spain, are evoluating at term towards a depopulation.
The demographic weigh of the continents
- Le poids démographique par continent
- L’Afrique sera plus peuplée que l’Europe
How much has it changed in a little more than a century ! 120 years ago,
Europe "weighted" heavy : a quarter of the humanity. It represents now no more than
the tenth. With 516 million inhabitants, to which one must add 150 million Russians,
Europe is behind the heavy weights that already are China and India.
The after-Mao has considerably modified the chinese demography.
The communism had encouraged the birthrate. After 1980, a voluntary, constraintly policy,
the one of the only child, has brought back an overflowing fecondity down to a threshold
inferior to the renewment of the generations. Such was one of the keys of the present
development of China, and, before it otherwise, the one of Japan and the asian dragon.
The chinese population is going to stabilize itself at one billion and a half.
It is not the same for its big neighbour, India. If in some indian states,
like Kerala, richer than others, the fecondity decreased, the subcontinent is not at the end
of its demographic transition, and its number of inhabitants is going to be heavier and
The most astonishing forecasts concern the african continent.
Its "demographic revolution" has already begun. The graph shows that it will have
a number of inhabitants equal to China and India, in 2020. The terms of comparison
are false, of course, because Africa is divided into about 40 states, but all the same :
only one century ago, Africa represented only 8% of the world population...
In 2020, 18 inhabitants of the planet among one hundred will be africans.
Nobody cannot know about this demographic bomb. The planet can
welcome new children ; the remaining question is in which conditions.
The next leader will still be devoted to the world population, analysed
this time not under the quantative angle, but under the qualitative angle.
Aux sources de l’article :
Cartes et graphes ont été empruntés au site de la généreuse et prestigieuse Ecole des Sciences politiques de Paris.
Autres sites génériques et statistiques :
Un site français, celui de l’institut national des études démographiques
Le site des Nations unies (United Nations Population Fund)UNPFA
Un site anglophone, accessible en français et espagnol, celui du Population Reference Bureau, le PRB