Do Car Seat Mandates Reduce the Number of Children Families Have?

A new working paper argues that car seat laws are discouraging moms from having a third child.


Are car seat mandates responsible for reducing the number of children born each year? A provocative new study claims that the steady upward creep in the ages at which states mandate children use a car seat is prompting women to either postpone or opt against having a third child.

The paper, by Jordan Nickerson of the Massachusetts Institute of Technology and David Solomon of Boston College, argues that most vehicles cannot fit a third car seat in the back row, necessitating the purchase of a larger car if a parent is going to cart around three children at once. That added cost, they argue, disincentivizes some women from having a third child.

"We find that when a woman has two children below the car seat age, her chances of giving birth that year decline by 0.73 percentage points," write Nickerson and Solomon, relying on U.S. Census Bureau data on the age and number of children for each woman surveyed. "This represents a large decline, as the probability of giving birth for a woman age 18-35 with two children already is 9.36 [percent] in our sample."

To tease out the impact of car seat laws, the paper controls for a number of variables, including urban density, household income, and whether a male parent is present. As states increase the car seat age, the more pronounced this effect becomes, as it's more likely that three children will simultaneously be required to be in a car seat.

The nationwide average minimum age at which a child can ride in a car with just a seat belt rose from just under three years old in the mid-1980s to four years old by 2000. Today, the nationwide average is a few months under eight years old. This steady increase, the paper suggests, could help explain why fertility rates have declined in the past decade despite a long-running economic recovery that would normally encourage more childbirths.

These laws could also allow more children to live, of course, by saving their lives during car crashes, but the paper argues that the effect on birth rates is larger. The changes "prevented only 57 car crash fatalities of children nationwide in 2017," it reads. "Simultaneously, they led to a permanent reduction of approximately 8,000 births in the same year, and 145,000 fewer births since 1980, with 90 [percent] of this decline being since 2000."

Are Nickerson and Solomon right? Maybe, but there are reasons to be skeptical. It's a correlational study, and the authors have to control for a large number of variables to try to tease out the effect of car seat laws on fertility.

A post at the blog Less Wrong also questions the underlying premise of the paper, noting that parents could avoid the costs of having to purchase a larger car by buying narrower car seats, and that there are car seats on the market that would still manage to fit three abreast in even small cars.

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  1. “Are car seat mandates responsible for reducing the number of children born each year?”

    Along with abortion, professional development among women, and homosexuality.

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  2. Car seat regulations are a huge violation of parental rights. It is the parents that know what is best for their own children and the parents should decide if they use car seats or not. Another example of liberal government run amok.

    1. The ProTroll 2020

      Troll harder. Troll faster. Troll better.

    2. They leftwing authoritarians, not liberals. Liberals are more like libertarians with a heart.

      1. “Rare”

        Old school left classical liberals are slightly more common than Ivory billed woodpeckers but less common than pygmy white rhinos.

  3. Look at what people are buying and driving, even people without kids are buying things that would’ve been classified as a bus 30 years ago.

    The average vehicle marketed at moms right now has what, 15 rows of seats? I don’t think lack of seating is a real problem many people have, and I find it hard to believe that with all the costs involved with having children the marginal cost of a slightly larger vehicle is the deciding factor.

    1. There really isn’t a “slightly larger” option though. While its true that many vehicles have gotten larger most still only have 2 rows of seats, only the very largest have the third row (or are wide enough for 3 seats in one row)

      With most people driving a crossover or midsize SUV, getting that third row requires going all the way up to a full size like a Chevy Tahoe or Ford Expedition, which brings a whole host of other costs apart from the high price of the vehicle itself, such as gas, but also just the difficulty of driving and parking it in urban/suburban areas

      1. We used to have these things called “minivans” that quite elegantly solved that problem.

        Moms didn’t want to be seen in them, so people stopped making them for the most part. They were objectively better at hauling kids around than the crossovers we have now, but looking outdoorsy was more important.

        1. We used to have these things called “minivans” that quite elegantly solved that problem.

          I disagree with your comment above and now I understand. You’re compensating. I thought your comment above was weird because the VW *micro*bus rolled off the assembly line with more rows (and less linear feet of bench space than your average SUV) more than 30 yrs. before the first minivan did and conversion vans filled the minivan niche that nobody needed filled for almost 2 decades prior to the minivan. The problem with the minivan is that it doesn’t solve any problem elegantly. Not towing, not hauling, not people moving, not fuel efficiency, not sporting performance, adverse conditions…

          Mrs. Habit talked you into a minivan. You have my condolences, but I’m not buying your rationalizations.

      2. If you’re driving a mid-size SUV then you have a very wide car with room for three car-seats.

        And no one with a SUV has ever cared about how difficult it is to park – they just sort of nudge it in and call it good. Taking up two spots? I have kids. Halfway into the street? I have kids!

        1. That’s not been my experience. Its people with pickup trucks that do that around here, the soccer moms with SUVs usually stick to the small crossovers because they can’t park anything larger than a midsize sedan

          1. Which is ridiculous, because I can fit my ambulance in a parking spot just fine.

      3. Why don’t they design vehicles to seat children in such a way that aftermarket child seats would be unnecessary? Whatever deficiency cars have in that regard, it would seem easier to build in than to allow for an insert.

        1. Because what do you do for people who don’t need child seats?

          1. Arrest them for altering/removing the factory built-in child seats?

        2. Remember, you have the rear-facing seats for infants, the forward-facing seats for toddlers, and the booster seats for children. (While I think you could *technically* just use the rear-facing infant seats for all of them and be in compliance, I don’t think it would be very comfortable for a 7 year old.) So now you need to somehow include 3 different built-in seats. It hardly seems worth it.

  4. 8 years old? Holy cow!

    I have a friend who’s son was 70lbs at 5. (Dad played football). Kid looked 10. I am sure he was well over 100lbs by 8.

    My 60 lb 8 year old can’t really use a booster seat any more. Those numbers seem kind of crazy.

    1. And if that’s the average some states must be higher

      1. In the people’s republic of Asshatchusetts, kids under 13 must rise in the back seat and I think be in a car seat until 8

    2. I found out the UK is phasing in a requirement pushing it up to 12 YO or 135 cm tall.

    3. What seems kind of crazy to me is that car seating isn’t already built to be adjustable for different size passengers, the way they are for drivers and front seat passengers. Why should people have to buy a succession of cradles for this purpose, and laboriously install them and uninstall them depending on the passengers, instead of being able to crank some cranks or flick some servos to achieve the same thing faster?

    4. I was taller than my kindergarten teacher.

  5. The saving grace is that fewer liberals, liberaltarians, progtards, and commies are having fewer children. They will breed themselves out of existence especially when the anti sex league gets into full swing.

    1. …more liberals…I should not drink this early.

  6. Also helps explain why people are such fucking pussies. Jesus Christ, 8 year olds in a carseat? I think I was 5 when the first seatbelt law for children went into effect in my state and I was pissed that they were spoiling my good time in the car.

    1. Sitting in the front with my father, drinking a coke after we visited the house he was building…. I would have been 8, maybe 9, and about 70# (generously).

      Go back to the beginning of that…. “sitting in the front with my father”….. puts a smile on my face remembering the day. The weenies are giving up too much in an endless pursuit of safety.

    2. I never wore a seatbelt when I was a kid. They didn’t have them in the back of pickup trucks or in early/mid 1960s British sports cars (unless you optioned them). Even in cars equipped Mom would reach over with an arm or order me to get on the floor.The seatbelt remained unfastened. “Third row” seatswere in the cargo area of station wagons and if they were even actual seats you faced backwards, like a tailgunner. There were no seatbelt laws for adults until Iwas well into adulthood. I paid a $15 fine for not wearing one in my mid/late 30s..

      1. My parents had a wagon with one of those backwards rear seats. I loved riding back there.

  7. I think another factor is how much of a pain-in-the-ass it is to have to fasten three kids into car seats. Imagine a day out where you have to make four or more stops.

    1. Having been out with my buddy and his three younger kids, you’re not wrong. Though, at least his kids are smart enough to buckle themselves into them. Even the three year old. I mean, we double check, but I’ve never seen them get it wrong.

  8. I was born in 1971 and vaguely recall being in a car seat when I think I was 3. Now, our 7 year old still uses one and our 10 year old outgrew his last year. They are very expensive and a pain in the ass (the car seats not the kids), and are good at trapping cheez itz and various other grime underneath, so while not the deciding factor, definitely don’t put you in the mood to have another kid

    1. But the first thing wife and I said when we thought about having another kid was that we would need to buy a bigger car

      1. Had this conversation with my wife yesterday about having a 3rd child. She said that I’d have to get a bigger car as well so that I could fit 3 car seats. I’ve got a compact sports sedan that I track/autocross several times a year, so I very quickly determined that I was quite satisfied with only two kids.

  9. At least they will still able to make the decisions on their own. For now,

  10. I love Less Wrong but I think they may be wrong in this case. Parents can only buy narrower car seats if those seats exist. I do not remember any such options when I was in the market for kid seats. Nor, I think, is size alone the consideration. The hassle of reaching across to buckle a kid is in significant. Trying to do that over an already-installed seat to the middle seat would require more flexibility than I possess.

    1. I would ask what the reduce prevalence of ‘third’ rows in family cars is over the last two generations.

      I see no change – the vast majority of people have never had a vehicle with more than a backseat.

      So the it wouldn’t be the existence of a mandate but rather the increase in size of seats instead.

      I’d also call shenanigans on the idea that buying a larger car is difficult – vehicles are cheaper, as a percentage of income, than ever and there’s a massive used car market.

  11. Thinking that this is a casual factor is pretty absurd at face value unless you purposefully don’t think about any other factors whatsoever.

    1. I’m glad someone said it.

    2. Indeed.

  12. Well, at least it also reduces the need for abortions.

  13. That sounds stupid.

    1. Nobody uses car seats because of a legal mandate.

    2. Would it not be just as last likely that smaller cars were causing a reduction in family size?

    1. On point #2, good luck figuring out of it’s the chicken or the egg.

    2. It’s another study whose only purpose is to show the prevalence of p-hacking among grant seekers.

      1. Gotta agree on that point, this is pretty ludicrous.

    3. Actually, rather a lot of people use car seats because of the legal mandates. And many people continue to use them long beyond their personal preferences only because of the legal mandates.

      If that were not true, there would be zero tickets for non-compliance (which is patently untrue) and the laws would have been unnecessary since people would have been voluntarily complying long before the law was passed. We don’t, for example, have a law requiring people to breathe regularly. The laws were only passed because some people didn’t (and still don’t) voluntarily use car seats.

    4. 1. Nobody uses car seats because of a legal mandate.

      You are absolutely wrong on this. My state requires 4’8″ or 80 lbs. to be in a car seat. Once they were old enough to see over the dash and not fiddle with buttons I personally allowed all three boys to ride in the front seat without a car seat illegally. This attracted comments and ire from everyone under the sun, aunts and uncles, in-laws, nannies, other parents, Karens passing by, you name it. Nobody once made the statistical argument that the paper-writers are making, every time the argument boiled down to “It’s the law”. And it makes sense that they don’t understand shit about why, the first parenting class we sat through one of the sessions was on installing your car seat. The session was led by “an appropriately trained police officer”. If you take a survey asking why people buy car seats and only 5-10% of people say “Because it’s the law.” that’s because the other 90-95% have fully embraced the fact that there are 5 lights and would gladly tell you which of Big Brother’s features they love the most.

      I will absolutely agree to the overarching point you make below. It’s exceedingly likely that nobody’s having kids based on carseat laws. But the idea that nobody uses carseats because of legal mandates is unequivocal bullshit.

  14. Booster seats meet the texas requirements.

    Those fit 3 across.

  15. Better safer cars, better things like air bags, car seats for kiddos, seat belts. Hard to argue with those things.

    Truth is the government has driven a lot of it.

    Yeah I remember when lap seat belts were just ignored or did not exist. I also know from experience how people these days survive or have minimal injury from car injuries they would not have survived 20 years ago.

    Car seats for infants and toddlers is a no brainer. As the child grows so we know that regular seat belts are not designed to work until one reaches a certain height and weight. The straps need to go where they need to be so booster seats help do that.

    Nobody has all of the right answers for each family. My libertarian has a role for public health and safety. Just as we have traffic lights and rules about drunk driving.

    Most of us want to keep our kids safe in the car. Most of us do and do not read every government rule.

    “You who are on the road
    Must have a code
    That you can live by

    Because the past
    Is just a good-by

    Teach your children well“

    Graham Nash 1969

  16. correlation =/= cause

    If you then remove the supposed independent variable and the postulated response changes, then you have science, but until then, it’s just a theory. And you really need to do it a bunch of times to make sure.

    That’s why “social science” is actually “social studies” (and I’m being generous). It’s not a controlled experiment, and never will be. Which is why libertarianism is the least objectionable social philosophy, at least it doesn’t prescribe actions based on lousy science.

    1. Welcome to epidemiology.

  17. And btw, FTS! Kids rode whereever they were told by Dad (or Mom), and “sat down and shut up” with no more than a book to occupy us for many, many years.

    And we lived!

    1. Well we did. Which is not to say that better safety is not a positive good.

      You are correct it is correlative not cause related. So lower birth rates are no more related to better car safety than more Starbucks drive throughs in the same time period.

      1. Which is not to say that better safety is not a positive good.

        It’s not. Adequate safety is adequately good. Better safety is inherently excessive. Otherwise, absolute safety is absolutely good.

        You might argue that I’m making a slippery slope fallacy but let’s be clear; you’re currently further down the slope and advocating for sliding down further.

    2. You were better as kids than we were. There were always car arguments at the beginning of trips in my family.

  18. No. Next.

    1. No. That’s still no reason not to get rid of them. Next.


  19. I believe it. Every Thanksgiving I used to spend about an hour at the rental car center trying to get three car seats into a minivan (only a Honda is designed to hold three and nobody rents Hondas). Anything smaller can be completely impossible–most SUVs won’t fit three car seats unless they have a third row, and good luck getting a kid into a car seat in the third row.

    Even with a booster and two car seats it’s hard. I’m looking forward to trying it with two boosters, but I don’t think I’ll be let out of COVID jail until they’re all in boosters.

  20. Risk aversion is deadlier than actual risk.

    1. Risk might cost you the rest of your life. Risk aversion unequivocally costs you some of your life. Forcing your risk aversion on others…

      1. Raising kids with high levels of risk aversion creates snowflakes.

  21. Go to a five point restraint system. That takes care anyone above a toddler.

  22. As a middle class conservative, it was definitely a factor in family planning.

  23. What about (Chrysler) min-vans?. Our family has owned four and currently has two.

    We can put three in the 3rd row (really tight) but the ideal is two in the 3rd row, one in the Captain in the middle, the other middle Captain folded down, and remove the front center console so the front passenger can get into the rear. Once we had all 5 grand kids in the mini-van.

    If you don’t need something to express your masculinity or financial power, they are fantastic for under $30k to upper $40’s (luxury model). And you can haul a 4×8 sheet of plywood.

    Warning – they do have reliability issues. Particularly transmission, brakes and rear a/c.

  24. I remember a bunch of us riding in the back of our scoutmaster’s El Camino. It was fun. Just imagine if anyone did that now.

  25. I clicked the link. Here’s the title of the study. No kidding:

    Car Seats as Contraception

    1. There’s a link to a PDF which contains the contents of the study.

  26. Children are expensive. A car seat is the least of the expense. Many people that I know with children have extra car seats in grandma’s car as well. I guess the question is does a 3rd car seat require a purchase of a bigger car? Maybe, but then again each new child comes with a bundle of expenses. Car seat mandates for small child make sense. Yes, when I was a child seat belts weren’t required and there were no child locks. Once I almost fell out leaning against the door. Another time I cracked the windshield with my forehead when my grandmother had to stop suddenly. Luckily she wasn’t going fast, or else I would have gone through the window.

    If the third car seat makes you rethink having child number 3, then maybe you can’t afford child 3.

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  28. For all you naysayers, here’s my two cents as a mom with a single child.

    It’s not just the necessity of buying a bigger car that could fit three car seats – it’s the inability to carpool as well.

    We had a carpool of approximately five of us that lived on the same street that carpooled to school starting in kindergarten through the eight grade. But in kindergarten, if we’d all been required to be in car seats (or even booster seats), this would have been impossible. Even with a minivan or full-size SUV, it simply wouldn’t be worth it to move car seats and booster seats around like that. Installation (and in installation) is a process that makes me want to blow my brains out, usually.

    So in essence the government has made it impossible to set up carpools for kids younger than 8. Unreal.

    I can honestly say that I take these issues into account when attempting to consider how many kids we might have.

  29. Who cares? It not like we don’t have a surplus of people in this world. I doubt that I ever will start worrying about birthrates in my lifetime. Maybe some time in the future but I am guessing that is a long way off.

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