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

Child mortality.

2.0 would work if every 2.0 children then went on to have 2.0 children. Unfortunately, some will die before having their own children. In order to cancel out these shortfalls there has to be a (very slight) over-replacement rate.

That is less than 5% but more than 2.5% and rounding errors then kick in.

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