Why does it take 2.1 child births per woman to keep a country's population stable?

Question

I read that anything below 2.1 births per woman means that the population of a country is shrinking. Apparently, all of Europe have shrinking populations (not counting immigration). France has an average of 1.94 births per wormen, Germany has an average of 1.36, while the EU average is 1.52.

Answer 1

Simple, if there are not 2 people in each new generation to replace 2 people in the previous generation, the population will of course shrink. Since every society has about 50% women and 50% men, quick math shows that each woman on average needs to produce two kids to avoid population decline (replace the mother and the father).

You can ignore exactly what the men are doing with regards to fathering children, and just focus on the child-production of the average woman. Since some people will die in infancy or childhood, you need a little more than 2.0 kids on average, so we say 2.1 is the fertility rate needed to prevent population shrinking.

Answer 2

Several factors play into it, but the short answers are: 1) some people do not make it to child bearing age, 2) the proportion of men to women has always been slightly higher, so if women are the ones having the babies, then they have to have a few more to make up for the higher percentage of men.

Answer 3

It takes two to replace two.

It is currently the most practical replacement level as long as present man to woman ratio does not change drastically...by war, famine, or changing reproductive behavior.