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

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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?

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Anonymous 0 Comments

The replacement rate is calculated with respect to women who reach childbearing age. If you calculated it with respect to any female ever born, it would be exactly 2. However, not every female child survives to childbearing age. A replacement rate of 2.1 is consistent with 1 out of every 20 female children not reaching this age.

You might think it’s silly to calculate the replacement fertility rate like this, but the reason to do it is because it separates two pretty distinct issues. The first is the decision/ability of mature women and their partners to have children. The second is child (primarily infant) mortality.

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