As a 41 year old with one kid born prepandemic and not a second maybe a little bit because of the experience of raising a toddler durning the pandemic I’m surprised you didn’t discuss that more- or the effect of the millennials who did or didn’t manage to buy a house before rates went up. I expect those to influence some people to not have kids or to have fewer. I don’t think I know a representative sample - especially of 34 year olds but it seems likely that those are the effects that shifted from the 10s talk of tech workers freezing eggs to the natalism that started coming up postpandemic.
100% agree on housing being a big factor for delays in family formation since the Great Recession that is probably playing a big role. I should have included that.
Is it possible to train a model that predicts tempo/age at birth based on various survey/demographic information, like a "fundamentals" model in political prediction. And then see if that model (a) accurately captures current tempo changes and (b) accurately predicts quantum fertility when integrated?
It's not my field, I'm just looking around. But I do see people put together hazard-style functions of the choice to have a second-kid given a first; the problem is that agents are going to be forward-looking so it's hard to know how well the timing impacts the level outside of historical correlations.
In figures 4 and 5, the convergence of the lines is aided by a noticeable *drop* (not just flattening) in completed fertility among the oldest cohort (1980). Does this imply that women in that cohort suddenly had many children die? I could be misunderstanding the import here, but it looks strange to see such a drop.
It's probably due to sample size and noise; I average three years but it's going to be a bit noisy at this level of granularity of specific ages. I don't know if anything real driving that.
One thing to mention is that this is still slightly premature -- I'm a member of the 1981 cohort and one of my friends and fellow cohort members had a kid in 2025.
Wanted to point out the 1974 conundrum -- teenage pregnancy peaked in 1991 and fell every year after that. A big factor for why 1974 had the highest fertility was likely because they overindexed on teenage pregnancies. No data to assert this claim but it's a working theory
Thanks Mike, & welcome to demography ;). This is a great summary/dataviz of the cohort fertility trends & implications. I totally agree that the current birth rate panic overlooks how period fertility changes usually exaggerate changes in actual completed fertility. That's not to say that shifting births to older ages will "recoup" all of these drops at younger ages, but certainly some (non-trivial) portion. Of course, only time will tell, so it's wise to be humble about specific predictions (as in everything)! But given the current media saturation on this topic, I think it’s really important to help people understand what the current fertility rates can and can’t tell us, so thanks for this.
Very interesting post, but think it odd to draw cheery conclusions using only US data. The US has a fairly good fertility rate compared to many peer countries and has only seen a decline from about replacement very recently (as recently as 2009, US had a TFR of 2).
Naturally, analyzing only US data, and not the places with much lower, more persistent TFR drops, will lead to optimistic results!
If this data makes you optimistic about the US, that seems reasonable. If it makes you feel optimistic for Japan, South Korea, or Europe that seems unwarranted to me.
'If this data makes you optimistic about the US, that seems reasonable. If it makes you feel optimistic for Japan, South Korea, or Europe that seems unwarranted to me.'
As a 41 year old with one kid born prepandemic and not a second maybe a little bit because of the experience of raising a toddler durning the pandemic I’m surprised you didn’t discuss that more- or the effect of the millennials who did or didn’t manage to buy a house before rates went up. I expect those to influence some people to not have kids or to have fewer. I don’t think I know a representative sample - especially of 34 year olds but it seems likely that those are the effects that shifted from the 10s talk of tech workers freezing eggs to the natalism that started coming up postpandemic.
100% agree on housing being a big factor for delays in family formation since the Great Recession that is probably playing a big role. I should have included that.
Is it possible to train a model that predicts tempo/age at birth based on various survey/demographic information, like a "fundamentals" model in political prediction. And then see if that model (a) accurately captures current tempo changes and (b) accurately predicts quantum fertility when integrated?
It's not my field, I'm just looking around. But I do see people put together hazard-style functions of the choice to have a second-kid given a first; the problem is that agents are going to be forward-looking so it's hard to know how well the timing impacts the level outside of historical correlations.
In figures 4 and 5, the convergence of the lines is aided by a noticeable *drop* (not just flattening) in completed fertility among the oldest cohort (1980). Does this imply that women in that cohort suddenly had many children die? I could be misunderstanding the import here, but it looks strange to see such a drop.
(Drop from age 36 to age 38, in both figures)
It's probably due to sample size and noise; I average three years but it's going to be a bit noisy at this level of granularity of specific ages. I don't know if anything real driving that.
One thing to mention is that this is still slightly premature -- I'm a member of the 1981 cohort and one of my friends and fellow cohort members had a kid in 2025.
A detour I didn't do is that the BLS has extended their fertility survey until 50, since it does make a difference in the later years.
Wanted to point out the 1974 conundrum -- teenage pregnancy peaked in 1991 and fell every year after that. A big factor for why 1974 had the highest fertility was likely because they overindexed on teenage pregnancies. No data to assert this claim but it's a working theory
Thanks Mike, & welcome to demography ;). This is a great summary/dataviz of the cohort fertility trends & implications. I totally agree that the current birth rate panic overlooks how period fertility changes usually exaggerate changes in actual completed fertility. That's not to say that shifting births to older ages will "recoup" all of these drops at younger ages, but certainly some (non-trivial) portion. Of course, only time will tell, so it's wise to be humble about specific predictions (as in everything)! But given the current media saturation on this topic, I think it’s really important to help people understand what the current fertility rates can and can’t tell us, so thanks for this.
I don't mean to be insulting but this is a frankly ridiculous post.
The so-called "tempo adjusted fertility rate" is just the same as the total fertility rate from 15 years ago, give or take.
What do you think is more informative as to the state of fertility in 2025? The total fertility rate of 2025, or the total fertility rate of 2010?
The former, if you have any sense.
Its possible that women are not engaging with 30 odd year males addicted to video games. If it takes longer to find an appropriate mate, so be it.
Very interesting post, but think it odd to draw cheery conclusions using only US data. The US has a fairly good fertility rate compared to many peer countries and has only seen a decline from about replacement very recently (as recently as 2009, US had a TFR of 2).
Naturally, analyzing only US data, and not the places with much lower, more persistent TFR drops, will lead to optimistic results!
If this data makes you optimistic about the US, that seems reasonable. If it makes you feel optimistic for Japan, South Korea, or Europe that seems unwarranted to me.
'If this data makes you optimistic about the US, that seems reasonable. If it makes you feel optimistic for Japan, South Korea, or Europe that seems unwarranted to me.'
For Europe it also depends on the exact country.
For example, according to 'Our World in Data' women born in 1950 in Austria or Belgium had by their 42th year a cumulative fertility rate of 1.86; those born in 1980 by contrast had at their 42th in Belgium a cumulative fertility rate of 1.87 whereas for Austria this number had declined to 1.61. (https://ourworldindata.org/grapher/cumulative-cohort-fertility-rate-by-age?country=~BEL & https://ourworldindata.org/grapher/cumulative-cohort-fertility-rate-by-age?country=~AUT)
Just to provide an example of how much that can differ based on the country.
Terrific note Mike.