Emily Oster

8 min Read Emily Oster

Emily Oster

Everything About Car Seats

When to turn, when to stop

Emily Oster

8 min Read

I am not so old that I do not remember car seats as a child. However, I definitely do not recall them as a permeant fixture in the car. There were many, many car trips with three children and my grandmother in the back seat, the smallest child held (buckled!) in her lap. I doubt my family ever used a booster seat in the car, and by 8 or 9 I was permitted in the front seat. To be clear: my family was on the risk averse end. Seatbelts at all times, defensive driving, and so on.

Car seat rules have evolved over time. In the present moment: kids under 2 are in infant seats, usually facing backwards. Two to four brings the giant five-point-harness car seat (when we finally donated the last of these I can only describe my husband as gleeful). And, in many places, kids up to age 8 are still required to be in booster seats. Recommendations often suggest continued booster use up until the age of 12.

These regulations have accelerated since the 1980s, and especially since the mid-1990s. In a somewhat surprising fact, a recent paper argued that these regulations have impacted fertility. The idea is that people do not want to have a third kid because they cannot fit in another car seat. Seriously. That’s what the paper says. Almost a 1 percentage point drop in third births! Once you hit kid 3, you’ve got to go to a minivan. Maybe it’s not worth it?

For the most part, car seat behavior is dictated by these regulations. You should follow the law, period. But that doesn’t mean we cannot ask why these regulations are in place, and what the data says. And, in particular, I want to focus on two questions.

  • First: what’s the evidence on front versus rear facing for kids, especially those above a year.
  • Second, what is the evidence on booster seats for older kids.

Car seat transition #1: Front versus rear facing

Infants sit in an infant seat, and they face backwards. This is understood, accepted and, indeed, they will not let you leave the hospital until you show your child is in the car seat correctly. Recommendations have long been that children until the age of 1 year face backwards. In more recent years, this has moved to the age of 2. Some people push it further. Why two years? If rear-facing is safer, why should there be an age cut-off at all?

The idea is driven by the biomechanics of what would happen if you were in a car accident. Tests with crash test dummies sized between 1 and 3 years (i.e. this paper) suggest less risk of injury (to the dummies) with rear facing than forward facing car seats. These tests are very convincing, since they are run in controlled environments, with dolls equipped with fancy accelerometers.

Translating this to data in the real world has been more of a challenge. In 2007, a very influential paper was published comparing injury rates in crashes between children using forward versus rear facing car seats. You can see the paper here. Using data from the National Highway Traffic Safety Administration, the authors argue that children aged 12 to 23 months are five times as likely to be injured in a side crash if in a forward facing seat, and twice as likely overall. This paper played a large role in the push to staying rear facing for longer.

However: it has since been retracted.

In 2017, the journal was contacted by an outside researcher who had been unable to replicate the analysis. The original paper writers then revisited their analysis and found they were also unable to replicate it. The issue, according to the journal, was thought to be a mishandling of survey weights, which caused their sample size to seem bigger than it was (Stata peeps: I think maybe “fweight” instead of “aweight” but they do not give details).

The authors retracted the paper and redid the analysis, now with more years of data, publishing an update here. Their conclusion was that while the direction of the effect was in favor of rear facing seats, there was no significance and the effects were small (0.5% of children 12-23 months in forward facing seats were injured, versus 0.2% of those in rear facing. But the actual number of injuries was only 14 and 3, much too low to get any significance).

This is all consistent with a world in which the the biology/mechanics/theory shows that rear facing has advantages, but the real world data suggests these may be quite small. So small that we’d need more than the 20 years of data we have to figure them out.

You might ask, given this: what is the point of turning kids around, if there is any suggestion it is safer, why not have them ride that way forever? One reason is that as kids get bigger it gets very cramped and uncomfortable. Another is that they often prefer riding forward and for kids who are carsick (I am very attuned to this concern), forward-riding is often better.

Car seat transition #2: Out of the booster seat

Second big question: Does your kid need to be in a booster until they are 8 or 10 or 12? My older kid is quite tall and by the time she moved into a real seat she was as tall as some short adults. Was there any real point in maintaining the booster for so long?

(I’m focusing here on “boosters” in general, although most kids spend some time in five-point harness car seats, which combine a booster seat with a harness structure. I’ll try to dig into this transition another time, but data is limited. Here, I’ll tackle the question of transition out of any booster option.)

The arguments behind a booster seat are also based in biomechanics. Kids are short. Seatbelts are built for taller people. This means they are less well suited to protect little kids in an accident than to protect adults. Booster seats (or “belt positioning boosters” as they are sometimes called) are designed to get kids tall enough to optimize seatbelt functioning.

A number of years ago, Steve Levitt (of Freakonomics fame, but also a friend of mine) wrote several papers arguing that, in fact, booster seats didn’t protect kids from serious injury or death. This paper was subject to a lot of criticism and scrutiny. Notable to me, from a parenting standpoint though, is that they do find a reduction in less serious injuries. I would leave my kid in a booster even for that.

But even if you do not care about less serious injuries, follow-up work suggests larger safety improvements, even for older kids. One set of example papers are this one and this one which use data from State Farm Insurance on younger and older kids to examine the impact of booster seats on injuries. The authors argue that use of booster seats reduces injuries, even for kids 4 to 7. An obvious complaint with both papers, though, is that they use parent-reported injuries and parent-reported seat use. Variations in honesty or memory could bias results.

Better, I think, is this paper which relates variation in state booster laws to estimate the relationship between boosters and accident fatality rates. They find that fatality rates among 6 and 7 year olds dropped in places that introduced booster laws for those age groups, relative to those that did not. (They find similar results for 4 and 5 year olds but there is less variation in those groups so the results are weaker). I have some quibbles with the paper (I do not like their figure presentation) but this is a good approach to the problem and an important finding.

There isn’t any good data I can find on booster seats for kids beyond the age of 8, partly because they aren’t required which makes it hard to have any good variation (more careful drivers are likely to keep kids in boosters for longer, for example). But important to note is that it’s not so much age as size. A very tall kid may be ready to be out of a booster before a short one.

Bottom line here is that even though they are annoying, my read is that even in the absence of regulations it is a good idea to keep kids in boosters until they are fairly old. If you’re looking for a travel-friendly version, might I suggest the Bubble Bum?

Two Final Words

First: for any car seat transition, it’s not really age, but size. Especially on the issue of boosters, the concerns arise because kids are shorter than adults. This means that some of the choices about boosters should reflect the size of your kid.

Second: The most dangerous thing is for kids to ride unrestrained. No seatbelt or restraint is much worse than an incorrectly used one. This might be obvious but in case it is not: Click it or Ticket!

Two women stand on a balcony chatting. One is pregnant.

Feb 27 2023

6 min read

Your Best Parenting Advice

ParentData is 3!

Emily Oster
A line graph with pink, yellow, and blue dots representing life's ups and downs.

Feb 21 2023

3 min read

Wins, Woes, and Autism

Your stories for the week

Emily Oster
A toddler sits on a couch poking at an iPad and smiling.

Feb 16 2023

4 min read

Infant Screen Time and Academic Success

Infant screen time and breakfast cereal terror

Emily Oster
A teddy bear sits on a chair in a doctor's waiting room.

Feb 06 2023

11 min read

New AAP Guidelines on Childhood Obesity

What does the data tell us?

Emily Oster

Instagram

left right
Milestones. We celebrate them in pregnancy, in parenting, and they’re a fun thing to celebrate at work too. Just a couple years ago I couldn’t have foreseen what this community would grow into. Today, there are over 400,000 of you here—asking questions, making others feel seen wherever they may be in their journey, and sharing information that supports data > panic. 

It has been a busy summer for the team at ParentData. I’d love to take a moment here to celebrate the 400k milestone. As I’ve said before, it’s more important than ever to put good data in the hands of parents. 

Share this post with a friend who could use a little more data, and a little less parenting overwhelm. 

📷 Me and my oldest, collaborating on “Expecting Better”

Milestones. We celebrate them in pregnancy, in parenting, and they’re a fun thing to celebrate at work too. Just a couple years ago I couldn’t have foreseen what this community would grow into. Today, there are over 400,000 of you here—asking questions, making others feel seen wherever they may be in their journey, and sharing information that supports data > panic.

It has been a busy summer for the team at ParentData. I’d love to take a moment here to celebrate the 400k milestone. As I’ve said before, it’s more important than ever to put good data in the hands of parents.

Share this post with a friend who could use a little more data, and a little less parenting overwhelm.

📷 Me and my oldest, collaborating on “Expecting Better”
...

I spend a lot of time talking people down after they read the latest panic headline. In most cases, these articles create an unnecessary amount of stress around pregnancy and parenting. This is my pro tip for understanding whether the risk presented is something you should really be worrying about.

Comment “link” for an article with other tools to help you navigate risk and uncertainty.

#emilyoster #parentdata #riskmanagement #parentstruggles #parentingstruggles

I spend a lot of time talking people down after they read the latest panic headline. In most cases, these articles create an unnecessary amount of stress around pregnancy and parenting. This is my pro tip for understanding whether the risk presented is something you should really be worrying about.

Comment “link” for an article with other tools to help you navigate risk and uncertainty.

#emilyoster #parentdata #riskmanagement #parentstruggles #parentingstruggles
...

Here’s why I think you don’t have to throw away your baby bottles.

Here’s why I think you don’t have to throw away your baby bottles. ...

Drop your toddlers favorite thing right now in the comments—then grab some popcorn.

Original thread source: Reddit @croc_docs

Drop your toddlers favorite thing right now in the comments—then grab some popcorn.

Original thread source: Reddit @croc_docs
...

Just keep wiping.

Just keep wiping. ...

Dr. Gillian Goddard sums up what she learned from the Hot Flash  S e x  Survey! Here are some key data takeaways:

🌶️ Among respondents, the most common s e x u a l frequency was 1 to 2 times per month, followed closely by 1 to 2 times per week
🌶️ 37% have found their sweet spot and are happy with the frequency of s e x they are having
🌶️ About 64% of respondents were very or somewhat satisfied with the quality of the s e x they are having

Do any of these findings surprise you? Let us know in the comments!

#hotflash #intimacy #midlifepleasure #parentdata #relationships

Dr. Gillian Goddard sums up what she learned from the Hot Flash S e x Survey! Here are some key data takeaways:

🌶️ Among respondents, the most common s e x u a l frequency was 1 to 2 times per month, followed closely by 1 to 2 times per week
🌶️ 37% have found their sweet spot and are happy with the frequency of s e x they are having
🌶️ About 64% of respondents were very or somewhat satisfied with the quality of the s e x they are having

Do any of these findings surprise you? Let us know in the comments!

#hotflash #intimacy #midlifepleasure #parentdata #relationships
...

Should your kid be in a car seat on the plane? The AAP recommends that you put kids under 40 pounds into a car seat on airplanes. However, airlines don’t require car seats.

Here’s what we know from a data standpoint:
✈️ The risk of injury to a child on a plane without a carseat is very small (about 1 in 250,000)
✈️ A JAMA Pediatrics paper estimates about 0.4 child air crash deaths per year might be prevented in the U.S. with car seats 
✈️ Cars are far more dangerous than airplanes! The same JAMA paper suggests that if 5% to 10% of families switched to driving, then we would expect more total deaths as a result of this policy. 

If you want to buy a seat for your lap infant, or bring a car seat for an older child, by all means do so! But the additional protection based on the numbers is extremely small.

#parentdata #emilyoster #flyingwithkids #flyingwithbaby #carseats #carseatsafety

Should your kid be in a car seat on the plane? The AAP recommends that you put kids under 40 pounds into a car seat on airplanes. However, airlines don’t require car seats.

Here’s what we know from a data standpoint:
✈️ The risk of injury to a child on a plane without a carseat is very small (about 1 in 250,000)
✈️ A JAMA Pediatrics paper estimates about 0.4 child air crash deaths per year might be prevented in the U.S. with car seats
✈️ Cars are far more dangerous than airplanes! The same JAMA paper suggests that if 5% to 10% of families switched to driving, then we would expect more total deaths as a result of this policy.

If you want to buy a seat for your lap infant, or bring a car seat for an older child, by all means do so! But the additional protection based on the numbers is extremely small.

#parentdata #emilyoster #flyingwithkids #flyingwithbaby #carseats #carseatsafety
...

SLEEP DATA 💤 PART 2: Let’s talk about naps. Comment “Link” for an article on what we learned about daytime sleep!

The first three months of life are a chaotic combination of irregular napping, many naps, and a few brave or lucky souls who appear to have already arrived at a two-to-three nap schedule. Over the next few months, the naps consolidate to three and then to two. By the 10-to-12-month period, a very large share of kids are napping a consistent two naps per day. Over the period between 12 and 18 months, this shifts toward one nap. And then sometime in the range of 3 to 5 years, naps are dropped. What I think is perhaps most useful about this graph is it gives a lot of color to the average napping ages that we often hear. 

Note: Survey data came from the ParentData audience and users of the Nanit sleep monitor system. Both audiences skew higher-education and higher-income than the average, and mostly have younger children. The final sample is 14,919 children. For more insights on our respondents, read the full article.

SLEEP DATA 💤 PART 2: Let’s talk about naps. Comment “Link” for an article on what we learned about daytime sleep!

The first three months of life are a chaotic combination of irregular napping, many naps, and a few brave or lucky souls who appear to have already arrived at a two-to-three nap schedule. Over the next few months, the naps consolidate to three and then to two. By the 10-to-12-month period, a very large share of kids are napping a consistent two naps per day. Over the period between 12 and 18 months, this shifts toward one nap. And then sometime in the range of 3 to 5 years, naps are dropped. What I think is perhaps most useful about this graph is it gives a lot of color to the average napping ages that we often hear.

Note: Survey data came from the ParentData audience and users of the Nanit sleep monitor system. Both audiences skew higher-education and higher-income than the average, and mostly have younger children. The final sample is 14,919 children. For more insights on our respondents, read the full article.
...

Happy Father’s Day to the Fathers and Father figures in our ParentData community! 

Tag a Dad who this holiday may be tricky for. We’re sending you love. 💛

Happy Father’s Day to the Fathers and Father figures in our ParentData community!

Tag a Dad who this holiday may be tricky for. We’re sending you love. 💛
...

“Whilst googling things like ‘new dad sad’ and ‘why am I crying new dad,’ I came across an article written by a doctor who had trouble connecting with his second child. I read the symptoms and felt an odd sense of relief.” Today we’re bringing back an essay by Kevin Maguire of @newfatherhood about his experience with paternal postpartum depression. We need to demystify these issues in order to change things for the better. Comment “Link” for a DM to read his full essay.

#parentdata #postpartum #postpartumdepression #paternalmentalhealth #newparents #emilyoster

“Whilst googling things like ‘new dad sad’ and ‘why am I crying new dad,’ I came across an article written by a doctor who had trouble connecting with his second child. I read the symptoms and felt an odd sense of relief.” Today we’re bringing back an essay by Kevin Maguire of @newfatherhood about his experience with paternal postpartum depression. We need to demystify these issues in order to change things for the better. Comment “Link” for a DM to read his full essay.

#parentdata #postpartum #postpartumdepression #paternalmentalhealth #newparents #emilyoster
...

What does the data say about children who look more like one parent? Do they also inherit more character traits and mannerisms from that parent? Let’s talk about it 🔎

#emilyoster #parentdata #parentingcommunity #lookslikedaddy #lookslikemommy

What does the data say about children who look more like one parent? Do they also inherit more character traits and mannerisms from that parent? Let’s talk about it 🔎

#emilyoster #parentdata #parentingcommunity #lookslikedaddy #lookslikemommy
...

SLEEP DATA 💤 We asked you all about your kids’ sleep—and got nearly 15,000 survey responses to better understand kids’ sleep patterns. Comment “Link” for an article that breaks down our findings!

This graph shows sleeping location by age. You’ll notice that for the first three months, most kids are in their own sleeping location in a parent’s room. Then, over the first year, this switches toward their own room. As kids age, sharing a room with a sibling becomes more common. 

Head to the newsletter for more and stay tuned for part two next week on naps! 🌙

#parentdata #emilyoster #childsleep #babysleep #parentingcommunity

SLEEP DATA 💤 We asked you all about your kids’ sleep—and got nearly 15,000 survey responses to better understand kids’ sleep patterns. Comment “Link” for an article that breaks down our findings!

This graph shows sleeping location by age. You’ll notice that for the first three months, most kids are in their own sleeping location in a parent’s room. Then, over the first year, this switches toward their own room. As kids age, sharing a room with a sibling becomes more common.

Head to the newsletter for more and stay tuned for part two next week on naps! 🌙

#parentdata #emilyoster #childsleep #babysleep #parentingcommunity
...

Weekends are good for extra cups of ☕️ and listening to podcasts. I asked our team how they pod—most people said on walks or during chores. What about you?

Comment “Link” to subscribe to ParentData with Emily Oster, joined by some excellent guests.

#parentdata #parentdatapodcast #parentingpodcast #parentingtips #emilyoster

Weekends are good for extra cups of ☕️ and listening to podcasts. I asked our team how they pod—most people said on walks or during chores. What about you?

Comment “Link” to subscribe to ParentData with Emily Oster, joined by some excellent guests.

#parentdata #parentdatapodcast #parentingpodcast #parentingtips #emilyoster
...

Humility. That’s why. That’s the whole reason.

#emilyoster #secondbaby #parentingjokes #parentinghumor

Humility. That’s why. That’s the whole reason.

#emilyoster #secondbaby #parentingjokes #parentinghumor
...

Bug season is upon us. Besides annoyance, this can bring up safety concerns, particularly with ticks. They are carriers of diseases, most notably Lyme disease. So what’s the best course of action?

Prevention is key! I suggest:
⭐ Regular tick checks
⭐ Using bug sprays with DEET 
⭐ Wearing long sleeves and pants in the woods

Some parents worry about DEET, but repellants with up to 30% DEET are recommended by both the CDC and AAP. The data says you’re in the clear, so go for it. Enjoy your summer!

#parentdata #emilyoster #tickseason #bugbites #bugspray

Bug season is upon us. Besides annoyance, this can bring up safety concerns, particularly with ticks. They are carriers of diseases, most notably Lyme disease. So what’s the best course of action?

Prevention is key! I suggest:
⭐ Regular tick checks
⭐ Using bug sprays with DEET
⭐ Wearing long sleeves and pants in the woods

Some parents worry about DEET, but repellants with up to 30% DEET are recommended by both the CDC and AAP. The data says you’re in the clear, so go for it. Enjoy your summer!

#parentdata #emilyoster #tickseason #bugbites #bugspray
...