Key Takeaways:

* The total fertility rate (TFR), or the average number of births per woman over her entire reproductive life, is one factor affecting population growth. Trends in the TFR have implications for the world’s demography.

* Although poor countries have a higher TFR than rich countries, the rate has been declining in both for 60 years. This has narrowed the TFR gap between the poorest and richest countries from three children per woman to less than one child per woman.

* In rich countries, the TFR has been lower than the rate needed to maintain population levels for a few decades. But the TFR in low-income countries remains higher than the replacement rate.

Anyone have the stats on the distribution of children per woman? And does it vary by country? For instance, in a country with a TFR of 1.0 (say South Korea), is that generally each woman has one child? Or is it the case that about half the women have 2 children, and about half has no children? Seems like that could have societal implications if your society was essentially raised as only-children, vs having siblings growing up. Maybe someone has studied this in relation to China's One-Child policy? Also it seems like if you had the case where half of the women were having two children, you'd be on a glide path to something sustainable long term.