The single most important factor in population growth is the total fertility rate (TFR). If, on average, women give birth to 2.1 children and these children survive to the age of 15, any given woman will have replaced herself and her partner upon death. A TFR of 2.1 is known as the replacement rate.

Why is 2.1 the fertility rate threshold?

Why is 2.1 the fertility rate threshold? You might think the number should be 2.0 - two parents have two children, so the population stays the same size. ... Nations with higher childhood mortality also need a higher fertility rate.

Why is the replacement rate 2.1 instead of 2?

Rather, the findings indicate that there are many countries in the world where the rate of replacement is greater than 2.1, which is a direct consequence of higher levels of mortality and skewed sex ratios at birth, resulting from sharp gender inequalities.