Why is the replacement fertility rate 2.1 instead of 2.0?

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In summary, the reason for the difference in fertility rates between women who have children and those who don't stems from the fact that the fertility rate accounts for children who die before they are able to reproduce. This rate also varies depending on the situation, with developed countries having a lower rate of around 2 and undeveloped countries needing a higher rate. The fertility rate only considers women who live to the end of their reproductive life, so those who do not survive are not included in the calculation. Additionally, the sex ratio at birth also plays a role in the fertility rate, with an average of 1.05 males to 1 female at birth.
  • #1
swampwiz
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What is the reason for this? Does it have something to do with the fact that the women who don't have any children somehow contribute more to the statistic than women who do have children?
 
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  • #2
It accounts for the children who die before they have the chance to reproduce.
 
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  • #3
A corollary of #2 is that this rate depends on the situation. While developed countries will be close to 2, undeveloped countries will need higher rates.
 
  • #4
Ygggdrasil said:
It accounts for the children who die before they have the chance to reproduce.

OK, this makes sense - but shouldn't those non-survivors count as simply folks that go childless, and therefore be included in the denominator?
 
  • #5
swampwiz said:
OK, this makes sense - but shouldn't those non-survivors count as simply folks that go childless, and therefore be included in the denominator?
No, by definition the fertility rate is the expected number of children of a woman who lives to the end of her reproductive life.
 
  • #6
swampwiz said:
OK, this makes sense - but shouldn't those non-survivors count as simply folks that go childless, and therefore be included in the denominator?
People who don't reproduce still are people, they can't be reasonably considered as nonexistent.
 
  • #7
swampwiz said:
OK, this makes sense - but shouldn't those non-survivors count as simply folks that go childless, and therefore be included in the denominator?
How can you count someone that hasn't survived? (no longer exists.)
 
  • #8
The sex ratio at birth for humans is 1.05 males to 1 female at birth on average. So for 2.1 children there will be 1.076 males and 1.024 females. I guess this is the main contribution.
 

1. Why is the replacement fertility rate set at 2.1 instead of 2.0?

The replacement fertility rate of 2.1 is based on the assumption that not all children will reach reproductive age. This accounts for factors such as infant mortality and individuals who may choose not to have children.

2. What does the replacement fertility rate of 2.1 mean?

The replacement fertility rate of 2.1 represents the number of children a woman needs to have in her lifetime to replace herself and her partner in the population. This is necessary to maintain a stable population size.

3. How was the replacement fertility rate determined?

The replacement fertility rate is determined using mathematical models that take into account factors such as mortality rates, life expectancy, and fertility patterns. It is also based on observed fertility rates in different populations.

4. Has the replacement fertility rate always been 2.1?

No, the replacement fertility rate has changed over time as societal and environmental factors have influenced fertility patterns. In the past, it was generally lower due to higher mortality rates and the need for larger families for economic and social reasons.

5. What happens if the replacement fertility rate is below 2.1?

If the replacement fertility rate falls below 2.1, it means that the population is not replacing itself and is expected to decline over time. This can have significant impacts on society, such as an aging population and potential workforce shortages.

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