Hans Rosling does it again, giving a wonderfully simple presentation, making sense of gloriously complicated statistics.
We have preconceived notions of how the World's population is growing and we have our own explanations for this. In this TED talk Rosling takes on the subject of religion and babies and shows that the factors that lower the number of children born to each woman are educational, cultural and economic (although not wealth).
From Qatar's social trends document: "The most important factors are as follows: increased age at first marriage, increased educational level of Qatari women, and more women integrated in the workforce".
Rosling's usual wizardry with time phased graphs is complemented here by his explanation of why the World's population will peak at 10 billion, using the cardboard boxes that the conference notebooks came in. What a master of explanation he is...