Actually when you apply the correlation between rising income levels and lowering reproduction rates to the projections of rising incomes of those who are now p

Actually when you apply the correlation between rising income levels and lowering reproduction rates to the projections of rising incomes of those who are now poor and reproducing at (relatively) high rates, global population is expected to start falling in as little as 20 years (admittedly this is a political topic and these is a wide range of projections available, including many who foresee an increase to 15 or 20 billion in 100 years). Either way, what's causing infertility is quite obvious - economic prosperity does.