Demographic transition

The term demographic transition (English demographic transition ) or demographic transformation describes in demography a typical course of the population development of states or societies in several phases. First the death rate falls and then the birth rate with a time lag . In contrast, the term demographic changecan be applied to any change in the structure of the population. One could take Germany as an example, here the death rate is falling, due to the high medical standards as well as the birth rate, as a result of which the population is falling and aging.

The model of demographic transition is not a theory in the scientific sense , but a model description of population development. It goes back to the first approaches of Warren S. Thompson (1929) and Frank W. Notestein (1945), later it was taken up and refined by other authors. The model has found application:

for the ideal-typical description of the changes in mortality and fertility in the western industrialized countries (especially England and Sweden ),
for typing different countries with regard to their demographic development and
in investigating the causes of the transformation process.

4-phase model

4-phase model of demographic transition

The original model is divided into four phases:

Phase I ( high stationary )
- Strongly fluctuating birth and death rates, which are close to one another at a high level.
- No significant population growth with high demographic turnover.
Phase II ( early expanding )
- Scissors open when the death rate falls while the birth rate remains roughly the same.
- There is a surplus of births that is constantly increasing.
Phase III ( late expanding )
- Closing the gap: the birth rate is falling, and very soon faster than the death rate.
- The birth surplus is steadily decreasing.
Phase IV ( low stationary )
- The birth and death rates are very close together at a low level.
- No significant population growth with low demographic turnover.
Special form:
- Death rate overlaps birth rate and the population is decreasing.

For the states of the western world (including Western Europe , North America ), the following chronological classification can be assumed:

Phase I: pre-industrial times until around 1840
Phase II: 1840-1910
Phase III: 1910–1980 / 90 (with strong fluctuations due to the two world wars , the global economic crisis and the baby boom )
Phase IV: since the 1980s until today; due to low fertility rates (between 1.21 in Spain and Singapore and 2.0 in Ireland and the United States ) can only get through immigration a low population growth are obtained

5-phase model

Newer 5-phase model of demographic transition

In more recent works (from around the 1970s), a distinction is often made between five phases of the demographic transformation process:

Phase I - pre-transformative or preparatory phase ( agricultural society ):

High birth and death rates, which hardly differ from one another.
The death rate can fluctuate considerably and temporarily (due to diseases, epidemics, famine, wars) exceed the birth rate.
Very low population growth.

Phase II - early transformative or introductory phase (early industrial society):

The birth rate remains consistently high and can even increase slightly due to the improved health of women
Slow, mostly inconsistent decrease in the death rate.
The population gap is widening.

Phase III - medium transformative or reversal phase (transition phase):

Due to better medical care and improved hygiene, the death rate is falling to a very low level; the birth rate is slowly falling due to the changed generative behavior . In the past, you needed more children for retirement, as the high mortality rate meant that around 50% would die. Due to better medical care, a rethink is now starting and it is sufficient if you have fewer children, as these are also very likely to survive thanks to improved medical care. Furthermore, you save costs, since children between the ages of approx. 0-15 years are a major cost factor.
The population growth reached its highest level.
Usually during this phase the “demographic window” opens, which means that the majority of the population is between the ages of 15 and 65, i.e. of working age. This proportion is greater than the youth base (population aged 0 to 15) and the pension base (population aged 65 and over). So there are more people who generate something than people who have to be cared for. As a result, the country usually experiences an economic upswing.

Phase IV - late transformative or turnaround phase ( industrial society ):

The death rate is hardly falling any more; the birth rate, on the other hand, falls very sharply through contraception .

Population growth is falling and the population gap is closing.

Phase V - post-transformative or final phase ( post-industrial society ):

Birth and death rates are stable and low.
Population growth is low and hardly fluctuates.

Variable model

Variable model of demographic transition

The empirical demographic transition has not been the same in all European countries. It started in England and lasted about 200 years there, while in countries like the Netherlands or Germany it only lasted 90 or 70 years.

Not only the duration, but also the extent of the population gap differs in the European countries. An exception is e.g. B. France : The decline in death and birth rates occurred almost simultaneously. In contrast to other European countries, there was no significant increase in population due to a large scissor opening.

In order to take such deviations into account, the variable model of demographic transition was developed in the 1980s . With the help of different curves of the birth rate (g1, g2, and g3) and the death rate (s1, s2 and s3), which have different inclinations, different transformation processes can be mapped in the model. For example:

The course of the French transition is represented by the curves that are close together (s1 and g1); in Germany the curves are correspondingly further apart (s2 and g2).
In countries of the Third World , their course can be represented by the curves that are far apart (s3 and g3).

This means that the demographic transition model is flexible enough to allow states to be classified and typified with regard to their status in the process of demographic transition and the way in which it takes place.