The total fertility rate is contentious.
When demographers peer into the future, the key figure that they look at is the total fertility rate, or T.F.R.
In that same 40 years, Malawi's population quadrupled, and the total fertility rate now averages six children per woman.
That has a short-term effect on the total fertility rate.
The average age of mothers rose from 30.2 in 2014 to 30.3 years, and the total fertility rate in England and Wales decreased to 1.82 children per woman.
Much hangs on the question of the "total fertility rate" – or the number of children a woman has on average during her lifetime.
The total fertility rate of Africa is 88% higher than the world standard (2.5 children per woman globally, 4.7 children per woman in Africa).
By 2030, according to United Nations projections, the total fertility rate in sub-Saharan Africa could fall to three.
Americans especially like to zero in on the total fertility rate, or TFR, the average number of children a woman can expect to have during her lifetime.
The total fertility rate in the United States, a measure of the total number of children the average woman is likely to have, in 2011 was 1.89.
As in neighbouring countries, the total fertility rate (average number of births for each childbearing woman) has been under two below the world average since the 1970s.
