However this population growth is now turning into population aging and will probably be followed by a population slowdown. I'm curious if we will ever have more than 10 billion people total. Europe and Japan are currently experiencing a natural population decrease, with immigrants keeping their total population from decreasing. However the explanation for decreasing fertility rates isn't so clear. Economist Oded Galor has crunched some numbers and confirmed the following reasons:
First there is the theory that the higher demand for human capital during industrialization lead to a decline in fertility as parents concentrated more on the quality of their children rather than their quantity. Second, as the wage gap between females and males decreased, the increase in female labor force participation and the associated higher opportunity cost of having children for mothers reinforced the decrease in fertility.Also interesting is the reasons that don't seem to be true:
the theory that the emergence of financial markets made in less necessary for parents to have been adult children to support them in old age; the theory that a decline in mortality lead to a too high number of surviving children; and the theory that the general increase in income lead to a rising opportunity cost of raising children.