4 ms·

For those wondering, TFR = total fertility rate and means "total number of children born or likely to be born to a woman in her life time if she were subject to

by alehul 7y ago

For those wondering, TFR = total fertility rate and means "total number of children born or likely to be born to a woman in her life time if she were subject to the prevailing rate of age-specific fertility in the population". [1] Essentially, how many children a woman will give birth to, on average. If it drops below 2, population will begin to shrink. Edit: As the below comment thread points out, > 2 (~2.1) may be required to not drop. :) [1] http://www.searo.who.int/entity/health_situation_trends/data/chi/TFR/en/ http://www.searo.who.int/entity/health_situation_trends/data...

qeternity 7y ago
I guess this makes the assumption that each woman is impregnated by different men. If 10 women and one man had a TFR of 1.5 the population is still growing no?
- steve19 7y ago
  Populations usually have close to 50% split, although I think there are usually slightly more woman. Outside of war/post war its unlikely to have a situation where there are 10 woman to each man.
  - irrational 7y ago
    India has a history of favoring males, so many females are aborted. You are more likely to see 10 men to each woman.
    - ktta 7y ago
      >You are more likely to see 10 men to each woman So you are saying India's new-born gender divide is 91% men and 9% women? Abortion based on gender is illegal in India. Most (all?) gynecologists in India won't reveal gender due to this until a certain stage (20 weeks) in the pregnancy after which abortion is illegal (requires court order).
      - scbrg 7y ago
        Things that are illegal happen.
      - jpatokal 7y ago
        Illegal it may be, but there are many states in India where the sex ratio for babies is badly out of whack. https://scroll.in/pulse/834701/one-step-forward-two-back-indias-uneven-progress-in-correcting-its-gender-imbalance https://scroll.in/pulse/834701/one-step-forward-two-back-ind...
- mamon 7y ago
  If you mean: some weird tribe that has a population of 10 grown up women and one grown up men then yes, any TFR > 1.1 would mean population growth. But in normal circumstances you assume that there is an equal number of men and women in population. Or, to be more precise, you assume 105:100 men:women ratio, because that's what statistics show in most countries. That's why you need TFR slighly higher than 2 to have constant population size.
steve19 7y ago
Not to be pedantic but I think it needs to be a higher than 2 in order to not shrink. The number usually stated is 2.1. This is to account for people who die before having reproduced themselves.
- kbutler 7y ago
  ...and because more males are born than females. (105:100)
- birdman3131 7y ago
  Pretty sure that it already accounts for that. As far as I understand it is for the entire female population. Say you have 100 females. 25 have no kids 15 have 1 kid 25 have 2 kids each 15 have 3 kids 10 have 4 kids 10 have 5 kids This would be a 2.0 TFR and would lead to no shrinkage or increase. The 25 without kids would include those who die before reproducing. Now a potential reason it might need to be higher than 2.0 is if it is not a 50/50 split between male and female children. I vaguely recall that slightly more male children are born than girls but it averages out by adulthood because boys are slightly more likely to die doing something stupid. This may not actually be the case so do some research before quoting me on the more boys part.
  - 0xB31B1B 7y ago
    The academics/experts in the field generally consider 2.1 to be replacement level fertility because: Accidental deaths before having kids Gay/Lesbian kids Kids that “want” to have kids but for whatever reason are unable to
    - evv 7y ago
      > Kids that “want” to have kids but for whatever reason are unable to The opposite is also likely. People may have "accidental" kids, or they could change their mind. (I still agree that 2.1 is a good approximation, but it is also likely to vary on cultural and natural effects)
    - Wowfunhappy 7y ago

by alehul 7y ago

qeternity 7y ago

I guess this makes the assumption that each woman is impregnated by different men. If 10 women and one man had a TFR of 1.5 the population is still growing no?

steve19 7y ago
Populations usually have close to 50% split, although I think there are usually slightly more woman. Outside of war/post war its unlikely to have a situation where there are 10 woman to each man.
- irrational 7y ago
  India has a history of favoring males, so many females are aborted. You are more likely to see 10 men to each woman.
  - ktta 7y ago
    >You are more likely to see 10 men to each woman So you are saying India's new-born gender divide is 91% men and 9% women? Abortion based on gender is illegal in India. Most (all?) gynecologists in India won't reveal gender due to this until a certain stage (20 weeks) in the pregnancy after which abortion is illegal (requires court order).
    - scbrg 7y ago
      Things that are illegal happen.
    - jpatokal 7y ago
      Illegal it may be, but there are many states in India where the sex ratio for babies is badly out of whack. https://scroll.in/pulse/834701/one-step-forward-two-back-indias-uneven-progress-in-correcting-its-gender-imbalance https://scroll.in/pulse/834701/one-step-forward-two-back-ind...
mamon 7y ago
If you mean: some weird tribe that has a population of 10 grown up women and one grown up men then yes, any TFR > 1.1 would mean population growth. But in normal circumstances you assume that there is an equal number of men and women in population. Or, to be more precise, you assume 105:100 men:women ratio, because that's what statistics show in most countries. That's why you need TFR slighly higher than 2 to have constant population size.

steve19 7y ago

Not to be pedantic but I think it needs to be a higher than 2 in order to not shrink. The number usually stated is 2.1. This is to account for people who die before having reproduced themselves.

kbutler 7y ago
...and because more males are born than females. (105:100)
birdman3131 7y ago
Pretty sure that it already accounts for that. As far as I understand it is for the entire female population. Say you have 100 females. 25 have no kids 15 have 1 kid 25 have 2 kids each 15 have 3 kids 10 have 4 kids 10 have 5 kids This would be a 2.0 TFR and would lead to no shrinkage or increase. The 25 without kids would include those who die before reproducing. Now a potential reason it might need to be higher than 2.0 is if it is not a 50/50 split between male and female children. I vaguely recall that slightly more male children are born than girls but it averages out by adulthood because boys are slightly more likely to die doing something stupid. This may not actually be the case so do some research before quoting me on the more boys part.
- 0xB31B1B 7y ago
  The academics/experts in the field generally consider 2.1 to be replacement level fertility because: Accidental deaths before having kids Gay/Lesbian kids Kids that “want” to have kids but for whatever reason are unable to
  - evv 7y ago
    > Kids that “want” to have kids but for whatever reason are unable to The opposite is also likely. People may have "accidental" kids, or they could change their mind. (I still agree that 2.1 is a good approximation, but it is also likely to vary on cultural and natural effects)
  - Wowfunhappy 7y ago