The world population in 2200 will be about 250 million if if all countries have a total fertility rate of 1.0 or less. This is the current situation in South Korea, China and Taiwan. Falling below replacement levels of 2.1 means that the average women no longer has an average of 1 daughter. If fertility rates go to 1.0 or less that means the total of all women have half of a daughter. This means the next generation (30 years later) has half as many fertile women. In 60 years there are 25% as many fertile women and in 90 years there are 12.5% as many fertile women.

The world is trending to a low-fertility scenario, global fertility is approaching 1.3 after 2050.

Poor countries like India and Bangladesh have fallen below replacement. This means the mother is not on average replacing herself with a daughter and the father with a son.