Barrons AP Environmental Science

2.72

Mexico

2.31

United  States

2.06

China

1.54

Russia

1.54

Japan

1.21

World   average

2.59

The two main effects of TFRs less than 2.1 without additions through
immigration are population decline and population aging. The greatest TFR
occurred during the post-World War II years (baby boomers). New immigrants
and their descendants are projected to contribute 66% of the expected growth by
2050.
Despite half of the world’s population having subreplacement fertility rates,
the world’s population is still growing quickly. This growth is due to nations
with above-replacement TFRs and a population momentum caused by large
numbers of younger females who have not had children as of yet.