Cont.

Africa. By far, the largest regional percentage increase in population by 2050 will be in Africa, whose population can be expected to at least double from 1.1 billion to about 2.3 billion. That projection, however, depends on the assumption that sub-Saharan Africa's total fertility rate (TFR, the average number of children per woman) will decline from 5.1 to approximately 3.0 by 2050. That decline, in turn, assumes that the use of family planning in the region will rise significantly. But recent surveys from many sub-Saharan African countries have indicated that TFR decline is either slower than projected or is not taking place at all. Only 20 percent of married women in sub-Saharan Africa use a modern form of family planning, the lowest rate in the world.
PRB population Reference Bureau