The iPhone explains 33–52% of fertility decline among women aged 15–44

https://www.nber.org/papers/w35310

by delichon • 1 month ago

102 51 1 month ago

nber.org

throwa356262• 1 month ago

You mean Instagram?

bel82• 1 month ago

I'll bite. Maybe it's not the iPhone itself, but social media.

I have seen studies about damages that social media can cause in behaviours. This might be one of them.

Smartphones are the catalyst to social media consumption as we know. Like people contantly on their phones everywhere instead of interacting with other people, for example.

sph• 1 month ago

Why not go further? It's the Internet as a whole. People socialising online, and online becoming an actual place people spend their entire lives within, free from the hard constraints of the real world, was the natural evolution of the Internet.

Plenty has been written about how any technological innovation leads to massive societal changes no one could foresee, and no one could avoid, but only analyze in retrospect.

FabHK3• 1 month ago

Indeed. When Germany unified, the birth rate in the formerly socialist East dropped by half. Certainly increasing uncertainty played a role, but there was also speculation that there wasn't much to do in the East except read, drink, and procreate, while the West had plenty of diversions.

bel82• 1 month ago

Yep. Even many of our jobs became remote and less social.

browningstreet• 1 month ago

Social media wasn't the thing it is today during the AT&T exclusive period.

macNchz• 1 month ago

That's the thing that jumped out to me here—iPhones themselves and everything you could actually do with one during that period were way different from today. There were effectively no endless feeds of content to consume, the phone screens were way smaller and less vibrant, push notifications only came out about halfway through.

I was age 19-23 during that period (in the "highest impact" age group from the article), and I think I used my phone more for coordinating in-person social activity than anything else at the time. Additionally on that—iPhones were not widespread in my cohort at the time, even at an expensive private college with many students from upper income families.

tgv• 1 month ago

It really did start in the time frame. Facebook opened in 2006. Twitter already existed and grew rapidly in that period. There were messengers. And because everything was slow, I suppose it could even take an hour to doom scroll Slashdot.

Mobile gaming might be another reason.

trollbridge• 1 month ago

I don't remember social media really being that significant from 2007-2011.

wmichelin• 1 month ago

Well, it was for many. MySpace, and then BBM, Facebook, and Twitter were absolutely huge at that time for the folks using them.

functionmouse• 1 month ago

https://jacobin.com/2026/06/birth-rates-capitalism-socialism...

ch4s3• 1 month ago

Ahh yes, Russian fertility was famously… lackluster in the Soviet period. So clearly capitalism caused fertility to decline.

applfanboysbgon• 1 month ago

Genuinely fascinating article. I had no idea that the DDR's fertility rate dropped to 0.8 after reunification. That said, I am skeptical of the assertions. Statistics can always be used to paint misleading pictures to support any narrative you like. For example, it neglects to mention that, according to the same source it links to show the birthrate dropped after reunification, that DDR's fertility rate was already down to 1.5 beforehand, well below replacement level. That strikes me as something of a lie by omission.

The emphasis on "it takes a village" seems strangely misplaced, as well. It presumes that culture is so malleable that a shift in government policy can change the culture overnight. Have East Germans completely abandoned their supposed previous culture of taking care of relatives/neighbors children after the fall? If there was a genuine cultural difference in communally raising children, and that was meant to improve fertility rates, you would expect to see higher fertility rates reflected regardless of the current government policy.

catoc• 1 month ago

https://www.tylervigen.com/spurious-correlations

hodder3• 1 month ago

"Entropy-balanced Poisson and synthetic difference-in-differences event studies"

LMAO does the author really take themselves seriously as they type that.

This author has no understanding of statistical methods. This sort of article is the reason why people distrust science. Not because the scientific method is flawed, but rather because nonsense like this get published.

dahart2• 1 month ago

What exactly is the problem with that sentence? Are you sure the problem isn’t that you don’t understand what it means?

Here are a few links explaining the terms:

https://pmc.ncbi.nlm.nih.gov/articles/PMC7384548/

https://en.wikipedia.org/wiki/Poisson_regression

https://lost-stats.github.io/Model_Estimation/Research_Desig...

I don’t know why people distrust science. Sure, it’s not perfect, and scientists, like all people are subject to human problems. But there’s nothing else in the history of the world with a better track record than science. I feel like the problem is that some politicians spread FUD and prey on people’s insecurities, and unfortunately it tends to work, disproportionately on people with less resources. The problem isn’t science at all; the problem is people and politics.

hodder3• 1 month ago

I know what a linear regression is and how to examine event studies, lol. What you don't understand is that the author is leaning on linguistics to insinuate strong evidence of causation where it doesn't exist. If this was a quant in finance, they'd be out the door in days.

"The problem isn’t science at all; the problem is people and politics."

Agree completely.

onlyrealcuzzo• 1 month ago

So... Let me get this straight.

Because people who had iPhones during the AT&T exclusive period has less kids...

They think there is no other possibly explanation besides the iPhone, because they looked at similar groups on different networks and in different areas that didn't yet have coverage for iPhones?

It definitely couldn't have been due to richer people having iPhones and having less kids, or people preferring iPhones who weren't going to have kids anyway??

Why definitely not? And why definitely iPhones or Smart Phones or whatever?

ilija1392• 1 month ago

Not every rich person got an iPhone. The rich people without an iPhone did not had equal amount of less kids. There are two groups, one has an iPhone, the other has not. The assumption is that two groups are big enough to have equal amount of people from any other group that can explain the decline in fertility, i.e. equal amount of rich/poor, educated, etc. They can control for this because they know which people had access to the iphone based on the AT&T network coverage.

At the end of the abstract they state the likely explanation of this seemingly spurious correlation: > National-survey evidence on time use and sexual behavior is consistent with the iPhone reducing in-person interactions, increasing pornography use, and reducing sexual frequency.

pbhjpbhj• 1 month ago

the iPhone reducing in-person interactions, increasing pornography use, and reducing sexual frequency.

Why would iPhone _particularly_ do that? I can see greater social media use, greater access to porn, would do those things. But that's common to smartphones in general.

FabHK3• 1 month ago

I suggest you read the abstract, at least. The fact that only AT&T had the iPhone back then resulted in a natural experiment: It was only available in certain regions. You can thus compare regions where it was available and where it wasn't, while controlling for "richer people" or "people preferring iPhones".

As a rule of thumb, if you look at something for 3 minutes and have some obvious questions, the scientists that looked at it for several years of their life in great detail might have had those same obvious questions as well.

virgilp3• 1 month ago

That's for the good studies. Let's not pretend that all published studies are honest. Unfortunately it is quite reasonable to be skeptical about extraordinary claims such as this one.

hansonkd• 1 month ago

Not to be pedantic and I agree with what you are saying but:

As a rule of thumb, if you look at something for 3 minutes and have some obvious questions, the scientists that looked at it for several years of their life in great detail might have had those same obvious questions as well

This does not mean that just because they had those obvious questions that they were properly resolved. Human history has a long track record of people who knew better but chose to ignore. In science there is an incredible pressure to have positive results rather than negative ones (IE nobody would care or know about this study if the title was "we looked and iphone doesn't explain 33-52% of fertility decline"

makeitdouble• 1 month ago

natural experiment: It was only available in certain regions.

This study treats ATT doing market research and progressive rollout through prioritized markets as a "natural experiment".

We could at least agree it's specifically chosen population, whatever ATT marketing dept had in mind when they planned the rollout.

tylervigen• 1 month ago

Right but the “certain regions” were affluent metro areas, the control group was rural counties, and the timeframe was the Great Recession.

Even the study authors acknowledge the severe risk of the huge confounding variable.

spwa4• 1 month ago

Because correlation is not causation. If A and B correlate there's 3 options:

1) A causes B

2) B causes A

3) C causes both B and A (in some order)

4) your correlation figure is bullshit (hence not counted in the 3 options, but certainly with news these days, it must be mentioned)

A famous way to illustrate where this goes wrong is to show a map which libraries that loaned out Harry Potter books, and a map of where poodles got raped. Very high correlation, and obviously an example of the 3rd option.

(obviously both were caused by population density, which leads to both library creation and poodle-related crimes. And probably non-poodle-related crimes)

wavemode2• 1 month ago

The 5th option is random chance.

That often results from p-hacking. In a world of infinite variables, if you look hard enough you are guaranteed to eventually find two completely unrelated variables that correlate with each other over a statistically significant period of time.

raincole• 1 month ago

Let me get this straight.

Let me get this straight, I believe one needs to read a paper to get it straight.

But I fully understand your knee-jerk reaction. That was my reaction when I read the title too. However, it seems to be a surprisingly well-thought analysis where all your points are answered (controlled).

If I read it more thoroughly I'll likely find flaws on the statistical methods. But it's not like the authors didn't have common sense.

Edit: unfortunately, enough people had the same knee-jerk reaction to get this thread flagged. We really need a way to vouch a thread.

rayiner2• 1 month ago

The paper has a section listing their controls, including income, poverty rate, race, etc: https://www.nber.org/system/files/working_papers/w35310/w353.... It's on page 11.

munificent• 1 month ago

Read section 5.

"Table 1 documents that treated counties (those with >90% AT&T 3G coverage) are substantially more urban, White, Republican-leaning, and affluent than control counties. To address this imbalance, we apply the entropy-balancing reweighting of Hainmueller (2012), which solves for the entropy-minimizing set of control-county weights that equalize the treated and reweighted-control means of a specified set of covariates."

jsw97• 1 month ago

Nobody at this level writes a paper like this, asserting a specific causal relationship, without considering exactly the questions you raised. The authors address your concerns. It's possible they did so poorly. But that is the case you would want to make. I'm tired of reading these low-effort takes on HN.

jfengel• 1 month ago

HN sees an awful lot of low-effort "research", which merit only low-effort takes.

This comes from the National Bureau of Economic Research, a well-respected organization. Even if you read only the title, the presence of "nber" in the URL means that it's worth more than just a hot take.

If the link were to substack, or phys.org, or various other content mills, then the HN kneejerk reaction would be warranted. Or rather, what's warranted would be silence, but at least the kneejerk reaction wouldn't necessarily be disproportionate to the quality of the work.

muizelaar• 1 month ago

"The fertility drop is concentrated among young populations and largely operates through declines in unintended births (Buckles et al., 2025), suggesting the operative margin may be less about the cost of raising a child and more about whether the relationships and sexual activity that produce children are forming at all."

prabhasp• 1 month ago

Worth understanding the idea of a natural experiment to understand what's being studied here - https://en.wikipedia.org/wiki/Natural_experiment

sizzzzlerz• 1 month ago

Well, with them constantly taking selfies of themselves they have no time for normal human activities

suncemoje• 1 month ago

And what does the iPhone have to do with that? What are the hypotheses? Can't tell from the abstract at least

pembrook• 1 month ago

This garbage "research" being on the front page of HN without getting flagged is a good indication we've reached peak irrationality in the current smartphone moral panic.

About time we revisted this: https://tylervigen.com/spurious-correlations

theonlyjesus• 1 month ago

It definitely was iPhones and not the first recession that started erasing the middle class in the United States

abhaynayar• 1 month ago

I've been able to quit short-form content, but does anyone have any tips on how to quit long-form content like YouTube or Netflix?

Also, why is this flagged?

OgsyedIE• 1 month ago

Sounds entirely accurate. Among all other technological advances, the biggest tracker of the very first wave of women's fertility decline in rural Europe in the late 1800s was access to electric lighting, which permitted rural women to make use of night hours for self-directed social, political and educational activity. (The source for this I use, although there are others, is The Subject of Virtue by Laidlaw)

Smartphones massively reduce the barriers to entry for self-directed career-based, social, political and educational activity (plus entertainment, but gambling addicts have differing fertility patterns so lesser degrees of it are useless to study). Outside observers may consider the real-world quality of such activities to be low, but the activity they enable people to do in their many brief lulls of free time between different daily tasks do fit into those buckets more than anything else. And the cumulative effect of all of them is to delay life milestones.

phyzix5761• 1 month ago

There's another interesting paper that talks about how in 2007 teens shifted their socializing to the smartphone. This led to a large reduction in teen fertility, as teens would spend more time communicating digitally rather than in person[0].

[0] https://papers.ssrn.com/sol3/papers.cfm?abstract_id=6676839

gomox• 1 month ago

Was the AT&T monopoly period of 2007-2011 have substantial social media adoption? Seems to me like the early iPhones were just a very capable phone & texting machinery.

The iPhone explains 33–52% of fertility decline among women aged 15–44

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