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I read through the underlying paper, and I don't quite understand their methodology. It seems like they're taking a bucketload of demographic information and th

• 7MinOfTerror 6y ago
  If you don't understand their methodology, you probably shouldn't be attempting to critique it. Why is it that internet forum commenters think they're qualified to examine the work of professional researchers who have spent years if not decades studying in their field? Edit: y'all are totally right, apparently a teenager who hasn't even completed their bachelors (in AI/CompSci) is qualified to read a public health research paper because they "demonstrate an understanding of statistics." This is functionally indistinguishable from mothers who jump on the internet and think they can read, interpret, and critique research papers on vaccines. "THIS PAPER DOESN'T CONSIDER THAT MERCURY IS TOXIC!!!"
  • sideshowb 6y ago
    The rest of gp's post exhibits good understanding of statistics. I suspect they're actually more qualified than "internet forum commentator". And it's good to be honest about what you do/don't understand, the fault could be in the explanation...
    • 7MinOfTerror 6y ago
      Understanding statistics does not mean you understand science or public health or research. "It wasn't explained to me, therefore it is invalid" is not valid.
  • ponker 6y ago
    Because internet commenters do not have other incentives at work like getting a grant or being tenured.
  • subroutine 6y ago
    Tell that to reviewer #1 and see how far it gets you.
  • anhner 6y ago
    Because there are statistics, and there are bad statistics. Indeed, only professionals are qualified to make studies, but anyone having at least a basic understanding of probabilities and statics can point out a badly thought out one.
  • onion2k 6y ago
    If you don't understand their methodology, you probably shouldn't be attempting to critique it. There's an implicit assumption in your comment that the methodology is good, and that anyone who criticises it must be unable to see that. Have you ever read the story "The Emperor's New Clothes"?
    • 7MinOfTerror 6y ago
      No. I'm giving the benefit of the doubt to people who are educated professionals in their field who have presented research that likely withstood some level of editorial and peer review....over a random internet commenter who starts their comment with "I don't understand their methodology" and then proceeds to attempt to critique it.
      • nakedlunch 6y ago
        Has anyone ever told you that you can disagree with another person without taking an indignant and rude tone?
      • czzr 6y ago
        Actually SSRN is a preprint server, so this has not been peer reviewed.
      • pkage 6y ago
        I should have been more clear. By saying "I don't understand their methodology," I was hedging around the statement "their paper does not contain an adequate explanation of their methodology due to the nature of the complex systems they are modeling. By omitting information on how they constructed their controlling variables (and indeed the full scope of what variables they controlled for), the authors (perhaps inadvertently) cast doubt upon the conclusions they draw from their results."
  • nakedlunch 6y ago
    Well... A. Perhaps this “Internet forum commentator” has more relevant experience than you understand, B. You don’t need to have years of scientific study to understand statistics and C. Plenty of bad science gets published every year in journals.
  • OneGuy123 6y ago
    You could be the worlds best expert on X but a highschool student with some basic statistics could easily invalidate the experts conclusions. And the highschool student would be right, and the expert would be wrong. It doesn't matter how much of an expert you are if your conclusions are wrong because you don't know statistics. If anything, an "expert" like that is actually a complete fraud.
• wcoenen 6y ago
  Did you read it before it was posted? It's a 50 page paper... I skimmed a few parts, and it looked plausible to me. For example, they studied the history of car seat laws in different states and correlated that with fertility data. If you have data from before and after certain law changes, and from states with/without certain laws, I can see how you could tease out the effect.
  • usrusr 6y ago
    And yet even if influence of car seat laws can be fully proven, it will be an influence on the wish for not having a third child, not a means of pulling through with that wish. Yet the title claims the opposite. Contraception and motivation to use contraception (or motivation to avoid need for contraception) are not the same thing. Note that I don't consider this inconsistency a mistake by the authors but as a playful deliberation instructing the reader in how to read the article.
    • gambiting 6y ago
      So taken to its logical extreme - was China's "one child" policy, where having any more kids after the first one was heavily fined - was that fine a contraceptive? Or not? I'd argue that it was, because it prevents pregnancy, but not in the biological "stops the egg from being impregnated" sense.
    • dash2 6y ago
      It would make having a third child more costly, not alter people’s preferences. (If chocolate bars double in price, that doesn’t influence your wish for chocolate. It just makes it more expensive to satisfy.)
      • usrusr 6y ago
        And yet people would willfully avoid buying chocolate. You are deliberately putting desires and intent in a single jar, but they are neither the same nor interchangeable. Desires can be conflicting amongst themselves (it's not even rare) while intent is the aggregate of desires, necessities, and, yes, outside power. Contraceptives are a means of achieving intent, not of altering it.
• em500 6y ago
  > It seems like they're taking a bucketload of demographic information and then trying to control for every other possible factor that could affect fertility rates to isolate the effect of car seat laws. I'm skeptical that it's even possible to control for all of those variables. Even assuming that they perfectly model the factors they do account for, it's perfectly possible that there are more underlying factors. This is true, but it's true for almost every observational study, and IMO too easy a dismission. You can use this reasoning to dismiss, or more likely, to cherry-pick probably 95% of all scientific results from economic/medical/social/nutricion/climate science. Just imagine the actual mechanics of setting up a proper Randomized Controlled Trial of seat belt safety! Back to the actual study, the reasoning appearch to hinge on the variation of outcomes between 1) having a 2nd and 3rd child 2) between car and non-car owning families 3) accross different states in the US with different introduction dates between car seat laws. Of course, their might still be lurking confounders, but the presumption that this is really caused by car seat laws sounds quite convincing to me[1]. I'd say the onus on sceptics in this case is to actually propose some possible confounders that might explain variation in all of 1), 2) and 3). [1] Disclaimer: I haven't gone through the details of the paper to see if the idea is actually well executed. This paper is likely headed for a serious economic journal, where it typically goes through at least days of labor to scrutinise the execution/details/methodology in peer review. I'm not invested enough to volunteer for that.
  • ema 6y ago
    > You can use this reasoning to dismiss [...] probably 95% of all scientific results from economic/medical/social/nutricion/climate science. Most researchers are incentived to churn out as many papers as possible. Most people who are making research grant decisions have little incentive to give grants to substantial science over insubstantial science that merely looks good. After all they're unlikely to face career consequences for funding science which doesn't replicate. Many of the people involved in the production of science are disincentivezed to point out problems with the process of science because science funding depends on science being highly esteemed, which only indirectly and with significant time lag depends on the effectiveness of science. All this leads me to the conclusion that, yes, it is entirely possible that 95% of science in those fields (and maybe others) is junk.
• jerome-jh 6y ago
  Read only the abstract, but this sounds very plausible. Trying to replace my 2005 car, I am quite surprised current models of the same exterior size have much less interior space and many would not fit a young adult and 2 kids (my situation). Is there any engineering reason behind this? I would rather think there are commercial reasons.
  • wiredfool 6y ago
    I think a lot of it is crash safety ratings and interior airbags. We fit three small kids in a 2004 Focus Wagon, but it was an exercise in finding the exact seats that would fit.
  • Phrodo_00 6y ago
    Crumple zones and airbags take space. Roofs that can handle the car being flipped without deforming enough to hurt you need chunkier pillars (I really lament this, makes visibility a lot worse)
    • jerome-jh 6y ago
      Mine has all the airbags a current car would have, so I do not believe this is the actual reason. It has a lesser crash rating than modern cars, but the reason is there are structural elements that drivers legs could hit in a crash (https://www.euroncap.com/en/results/honda/cr-v/15568 https://www.euroncap.com/en/results/honda/cr-v/15568). Basically I thing the car is too stiff for Euroncap, but it does not make it less safe in my opinion. Crumple zones are sized for standardized impact tests. Acoustic stuffing probably takes much space two. And I agree for the pillars.
      • throwaway0a5e 6y ago
        I'm not sure why you're being so heavily down-voted since you're quite close to the truth. Airbags mostly take up what on other cars was dead space behind trim. Crumple zones #1 function is to buy time for the airbags to deploy between when the front of the vehicle starts slowing in a crash and when the cabin starts slowing. Think about it, if the cabin decelerated at the same rate as the front bumper the occupant would be half way to the steering wheel by the time the bag finished exploding and they'd get hit in the face with an exploding airbag. Crumple zones #2 is deceleration and is tuned for a specific speed of impact. They can be thought of as a single use coil spring without a damper. Too slow of an impact and they do little to nothing (no big deal because it's a slow impact). Too fast and you will blow right through your available travel and bottom out hard. Because the car manufacturers are not staffed by idiots they respond to incentives and tune their crumple zones to be most effective at crash absorption at the high end of the speeds they are tested at. Most of the increase in "wall thickness" so to speak, of vehicles is from pillars and body structure that increases in width (to get more strength without adding too much material and weight). Then the trim is layered over that and that means you not only lose the space where the reinforcements are but over the whole vehicle.
• throwaway0a5e 6y ago
  > as the variation between model and reality could easily be noise from the control variables rather than from a relationship between car seat laws and fertility. Especially when you consider that something like a state law mandating car seats is only gonna exert upward pressure on the cost of a kid for people with higher incomes. Basically the poors are gonna pile into whatever vehicle they have and the law can fuck off. Nobody says "gee we shouldn't have another kid because we'll need X, Y and Z' (one of those being a bigger car in this case). That's just not how people make decisions at that level. If you want a kid you get a kid and you roll with it. You know it's gonna be expensive but you just deal. Controlling for income is really really hard since basically everything about lifestyle has some relation to income. Controlling for income with sufficient accuracy that you can tease out an effect that itself correlates with income is gonna be neigh on impossible when you're looking for something that's a 2nd order effect. This is like trying to predict trout populations in Canada by chemically analyzing reindeer piss in Russia. You can do it but it's an exercise in measurement and it's gonna have zero practical utility since sooooo many other things will have affects that dwarf those of what you're measuring. I think it's far more likely that rear seats have shrunk and car seats have grown because fertility rates have declined and regulators and manufacturers are therefore emboldened to do things that would be laughable in a world where three kid households were more common.
  • davidsolomon 6y ago
    > That's just not how people make decisions at that level. If you want a kid you get a kid and you roll with it. You know it's gonna be expensive but you just deal. The way I think about it as that these laws only need to affect some families that are on the margin. Are there some families that are just on the fence and tossing up whether to have a third child? It seems likely to me. As long as this cost is a significant one, it just needs to move the needle for these groups to show up in aggregate effects. Lots of people will make the same choice either way, whether it's to have a third child or not have a third child. Our predictions are for people right on the margin. >Controlling for income is really really hard since basically everything about lifestyle has some relation to income. We use county-by-year fixed effects to take out the average effect of birth rates in that county and year, whatever form that variation takes. So if it's just that Cook County in Illinois got richer one year and so had more children, this will be absorbed by the fixed effects, and our car seat impacts are considered relative to this baseline. We also control for birth rates for that number of children and age combination, so we're comparing essentially two families with a six year old and a three year old, but in one state/year they both have to be in car seats, and in the other one only one child has to.
• davidsolomon 6y ago
  Hi, I'm one of the paper authors here. Happy to answer questions. Here's how I think about our methodology. Car seat laws generate an unusually sharp prediction for births that can be distinguished from a lot of competing effects (not perfectly, of course, but compared with a lot of other demographic effects) We're not testing whether the state and years with more stringent car seat laws have lower birth rates. That could be due to tons of stuff going on in those states. We're not even testing whether the states and years with more stringent car seat laws have lower birth rates just for third child births. That could be relatively fewer things, but still a lot. Rather, we're testing whether states and years with more stringent car seat laws have lower third child birth rates specifically for families whose first two children are below the mandate for their state and year. And this mandate is itself changing over time for both states and years, so we're talking about different ages of children in question depending on which state and year it is. This clearly doesn't rule out everything. But the set of candidate explanations for what else could be going on for those specific families in those years is a lot smaller than the broad demographic effects we started with.
  • stanfordkid 6y ago
    It seems like low birth rates are pretty correlated with wealth. It also seems like liberal states, which are generally wealthier, have much more stringent regulatory policies -- such as mandatory car seats. How deeply do you understand these very clear confounding variables?
    • davidsolomon 6y ago
      In terms of the general effects that some counties are richer than others, and some years people are richer than others, this will be captured by our fixed effects that control for overall birth rates for each combination of county, year, and number of children. So all effects are measured relative to other two child families in the same county and year. This captures the large majority of other regulatory and social changes that might be happening in that county and year. Next, we also add income by year and income by county fixed effects. So if richer people in a given county have more children relative to the average of all two child families in that county and year, we'll also control for that. If richer people in a given year have more children compared to the average of all two child families in that county and year, we'll capture that too. The point isn't that you need to add every one of these complicated fixed effects to find our result. It shows up in simpler tests too. It's just that you can control for a lot of potential confounding effects, and it still seems to be there.