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 UN projections for the global population growth rates, which have been produced since the 1950s, have a good track record in projecting the size of the global population as we will show in the last part of this entry.
Population growth is driven by three different factors: mortality, fertility, and population momentum.
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.
There are three primary determinants of global population growth: mortality, fertility, and population momentum.
The global improvement falling mortality – seen in increasing life expectancy around the world and falling child mortality in every country – contribute to an increase of the world population.
, population growth has slowed considerably: The fastest world population growth rate was already reached in the late 1960s, and it has been falling since.
While the world population increased by 2% annually in the late 60s it has now slowed to an increase of just about 1%.