This is from The Economist:
Sub-Saharan Africa’s dependency ratio (the population younger than 20 and older than 64 versus the population between those ages) is 129:100, compared with 65:100 in Europe. Sub-Saharan Africa is expected to have a worse dependency ratio than Europe even in 2050.
… There is nothing inherently African about large families. Botswana’s fertility rate is 2.6, down from 6.6 in 1960. South Africa’s rate is 2.4. And although the UN has a good record of predicting global population growth, it has got fertility projections badly wrong in individual countries. Sudden baby busts in countries like Brazil, Iran and Thailand caught almost everyone out. Could Africa also spring a surprise?
On balance, I am less alarmed by population growth in Africa than most observers. Female gross secondary school enrollment is at an all time high. Urbanization is apace. Family sizes are most likely to shrink at faster rates than anticipated by current models.