Why is the replacement level for population considered 2.1 and not 2?

Question

I understand that many women will not have kids or will have only one kid, or that child mortality is involved but still a fertility rate of 2 means that ON AVERAGE every woman will have 2 kids. This means that every woman and man will be replaced, including the children that die young if the rate of 2 lasts (the newborn females will also have on average two kids). So why isn’t a fertility rate of 2 enough to replace the population?

In: 701

Answer 1

i can think of three factors right away.

1. Because a %age of women dies before they have offsprings. Thus we need slightly more than 2.1 per woman.
2. Because some women arent able to produce children.
3. Because the ratio of men/women is not perfectly 50/50 but more commonly 51% males and 49 females.