For this reason, there are minor differences on numbers on the tables but the general trend stays the same. Table 4 indicates seven different projections, based on the assumptions of different birth rate change. While the medium variant projections expect that TFR for Africa would decline to 2.04 by 2045-2050, the high/medium projections assume that TFR may not decline to 2.17 level until 2095-2100. On the other hand, however, the high-variant projections for Africa, indicates that it would decline to 2.50 by 2045-2050, while the low-medium variant shows its decline down to 1.96 by 2095-2100. The low variant projections project a decline to 1.70 level by 2035 to 2040.
Attention should be paid here that projections were made using different assumptions which are for medium, high/medium, high variants and those of analytical variants where NRR=1.0 which is a level of population replacement, and finally those of the constant fertility of 1990.
According to medium variant projections, the world population would reach 11.5 billion by 2150 and by the last half of 22nd century it would become the 12 billion level and then get stabilized. On the other hand, high/medium variant projections suggest that it will not stabilize until later. In 2150, the population would reach 20.8 billion which is 80% more than what the medium-variant projections. According to the high variant projections, the world population would reach 28 billion in 2150 and it would not stabilized at all. On the other hand, projections made using the constant birth rate of 1990, show that the world population in 2150 would be 694.2 billion, an incredible number.
Finally, though out of order, according to the projections made under the assumption of NRR= 1.0, even that population continues to grow for a while and population of 2150 is estimated to be 1.6 times more than that of 1990. This is what is called population momentum, population increase by inertia.
Among the above mentioned future world population projections, the medium variant projections seem to project fertility decline in developing regions and it seems to forecast rather optimistically for Africa. Therefore,
