Then in the 1960s the fertility rate in the ‘less developed regions’ started to fall and another decade later the fertility rate in the ‘least developed regions’ followed this decline.
The fertility rate of the world was still at 5 children per woman until the mid-1960s.
In contrast to this the WC-IIASA projections are also taking into account the qualitative assessments of 550 demographers from around the world which the WC-IIASA researchers have surveyed to gather their ideas on how the population change in different parts of the world will play out.
They then combine the country specific expertise of these researchers with similar quantitative information that the UN and others rely on as well.
But in addition to their main Medium projection the UN Population Division are additionally publishing a High and Low variant, which simply assume that the total fertility rates are 0.5 higher and 0.5 lower than the Medium variant by the end of this century in every country.
But there are also a number of other institutions that are preparing their own projections of the world population.
The visualization below shows the total fertility rate by the level of development and includes the UN projections through 2100.
Until 1950 the fertility rate in the ‘more developed regions’ had already declined to less than 3 children per woman.
The decline of fertility rates on the other hand, – the number of children per woman – reduces population growth.
The global average fertility rate was 5 children per woman until the end of the 1960s and has halved since then.