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> and 2) four crash tests that were run by an anonymous test center. He addresses that criticism directly in the video by saying that there are another 45,000+

> and 2) four crash tests that were run by an anonymous test center. He addresses that criticism directly in the video by saying that there are another 45,000+ incidences of real-world crash data that have been analyzed. > "Effectiveness of Child Safety Seats vs Seat Belts in Reducing Risk for Death in Children in Passenger Vehicle Crashes" [2]; it's freely available, but I have yet to read it. Well, if you did read it(you don't even have to read it, just look at the easy-to-read tables), you would see that their data results match exactly with what Levitt is saying -- there is not real difference! However, their conclusion is different, because they have an additional variable, which is that they determine if that car seat was "seriously misused". I have to admit, I never heard this before and it is hard to believe, given that conventional wisdom says that child seats are safer, however, the data does seem to back up what he is saying. It really sounds to me like you are the one that is falling victim to exactly what he is claiming, "It must be right, because that is what everyone believes--plus it is kids!" You do know that instead of knee-jerk criticizing someone for believing what an economist says, you can go through his data, show where his methods, data, or conclusion is wrong and help everyone! (... and be famous in the process)

zrail 10y ago
The paper concludes that there is a 28% reduction in risk of child death when using a restraint system vs just a seat belt (95% CI) and a 21% reduction in risk of death even if the system is misused. How is that "no difference"?
- mhuffman 10y ago
  I addressed that in my comment. Their numbers are practically identical, but their conclusion is different, because they make a determination on whether a car seat was "seriously misused". Further, Table 1 says that seat belts had a non-fatal rate of 99.89% and restraint systems had a non-fatal rate of 99.88%. Hell, they flat-out say that they had to adjust it to get those numbers: "Table 2 summarizes little difference in the unadjusted risk for death between users of child restraint systems and users of seat belts (RR, 1.03; 95% confidence interval, 0.72-1.46). After adjusting for seating position, vehicle type, model year, driver and passenger ages, and driver survival status, children in child restraint systems had a 21% reduction in risk for death compared with children in seat belts, although this difference was only marginally significant (RR, 0.79; 95% confidence interval, 0.59-1.05). After excluding the cases of serious child restraint system and seat belt misuse from FARS, children in child restraint systems had a 28% reduction in risk for death compared with children in seat belts (RR, 0.72; 95% confidence interval, 0.54-0.97)." It seems that they are trying to get to that conclusion.
  - mcguire 10y ago
    "Further, Table 1 says that seat belts had a non-fatal rate of 99.89% and restraint systems had a non-fatal rate of 99.88%." Um, no, I'm afraid. Table 1 describes the characteristics of the data set. 99.89% of the "seat belt" sample were non-fatal accidents and 0.11% were fatal; that and the row immediately above it sum to 100%. A fatal accident is defined as one in which someone died, including a pedestrian.
    - mhuffman 10y ago
      I am afraid that you are mistaken. You will note that they say: "Within FARS, we identified 7813 children aged 2 through 6 years who were vehicle occupants restrained in a child restraint system or a seat belt in a nondrivable passenger car, van, pickup truck, or sport-utility vehicle that was involved in a crash with at least 1 passenger fatality between 1998 and 2003. Of these 7813 children involved in fatal crashes, 1096 children (14%) were killed." You will then note that in Table 1 for "Overall" the Fatal rate is 1096 (identical to the number of children, the 14% above, that were killed). You will also note that if you add together the FARS and NASS CDS numbers you will get 9246, which is the total number of children aget 2-6 from both and also the sum of 1096 and 8150 from the "Overall" column on Table 1. now that I think about it, it doesn't even matter. If the same relative rates are fatal and non-fatal (separately) that still says that they are practically equivalent. Also, it says so in the paper...
  - zrail 10y ago
    The result still seems compelling to me. If I can reduce the risk of my child being killed in a car accident by 28% (even if the raw numbers are small) I'm going to do it. I don't want to change the goal posts here, but death isn't the only thing these booster seats protect against. A properly used booster seat reduces the relative risk of non-fatal injury by more than half[1]. That is also extremely compelling to me. [1]: http://jama.jamanetwork.com/mobile/article.aspx?articleid=196677 http://jama.jamanetwork.com/mobile/article.aspx?articleid=19...
    - mhuffman 10y ago
- smileysteve 10y ago
  A 4 or 6 point harness for adults and mandatory bolsters would have a major effect on the fatalities too, but would likely result in fewer people wearing them. Hans and helmets would also save us all from airbags.
mcguire 10y ago
The easy-to-read tables match their results: "Results Compared with seat belts, child restraints, when not seriously misused (eg, unattached restraint, child restraint system harness not used, 2 children restrained with 1 seat belt) were associated with a 28% reduction in risk for death (relative risk, 0.72; 95% confidence interval, 0.54-0.97) in children aged 2 through 6 years after adjusting for seating position, vehicle type, model year, driver and passenger ages, and driver survival status. When including cases of serious misuse, the effectiveness estimate was slightly lower (21%) (relative risk, 0.79; 95% confidence interval, 0.59-1.05)."
- mhuffman 10y ago
  That is their conclusion (which I addressed in my comment). Read the table: Table 1 says that seat belts had a non-fatal rate of 99.89% and restraint systems had a non-fatal rate of 99.88%. They flat-out say that they had to adjust it to get those numbers: "Table 2 summarizes little difference in the unadjusted risk for death between users of child restraint systems and users of seat belts (RR, 1.03; 95% confidence interval, 0.72-1.46). After adjusting for seating position, vehicle type, model year, driver and passenger ages, and driver survival status, children in child restraint systems had a 21% reduction in risk for death compared with children in seat belts, although this difference was only marginally significant (RR, 0.79; 95% confidence interval, 0.59-1.05). After excluding the cases of serious child restraint system and seat belt misuse from FARS, children in child restraint systems had a 28% reduction in risk for death compared with children in seat belts (RR, 0.72; 95% confidence interval, 0.54-0.97)." If you read further down in their conclusions, they seem to have a real hard-on over Levitt. I am not saying that they are wrong, but the data (un-modified) supports Levitt's conclusion.
  - mcguire 10y ago
    I presume you mean this: "In a more recent series of analyses, Levitt4 and Dubner and Levitt11 used FARS data from 1975 to 2003 and, by various methods, directly compared the mortality with child restraint systems vs seat belts in children aged 2 to 6 years and could not demonstrate a difference in effectiveness. Levitt and Porter12 restricted the FARS data set to 2-vehicle crashes in which someone in the other vehicle (ie, the vehicle without the index child occupant) died, under the assumption that the distribution of restraint use among children in potentially fatal crashes is independent of whether someone in the other vehicle dies, after adjusting for various crash-related characteristics. "The precision of these previous effectiveness estimates and their relevance to today's fleet were limited by their reliance on FARS (the limits of which were presented in the introduction), by the inclusion of older vehicles and restraints, and by failing to control for the severity (potential unsurvivability) of the crashes. Our analysis based on a modern cohort of children involved in crashes in which the car was rendered undrivable addressed many of the limitations of these previous analyses and found effectiveness estimates for child restraint systems to be greater than that for seat belts alone, with estimates greater than those of both Levitt4 and Hertz.6" Levitt, et al, used only FARS data, which only records fatal accidents. A hypothetical accident where only the child would have died but that was prevented by the restraints would therefore not show up in the data, leading to the value of the restraints being under reported. Further, failing to control for the severity of the accident (which this work does using the survival of the driver) also undervalues restraints: if the car ends up as a ball the size of a grapefruit, it doesn't matter what restraints were used.

zrail 10y ago

The paper concludes that there is a 28% reduction in risk of child death when using a restraint system vs just a seat belt (95% CI) and a 21% reduction in risk of death even if the system is misused. How is that "no difference"?

mhuffman 10y ago
I addressed that in my comment. Their numbers are practically identical, but their conclusion is different, because they make a determination on whether a car seat was "seriously misused". Further, Table 1 says that seat belts had a non-fatal rate of 99.89% and restraint systems had a non-fatal rate of 99.88%. Hell, they flat-out say that they had to adjust it to get those numbers: "Table 2 summarizes little difference in the unadjusted risk for death between users of child restraint systems and users of seat belts (RR, 1.03; 95% confidence interval, 0.72-1.46). After adjusting for seating position, vehicle type, model year, driver and passenger ages, and driver survival status, children in child restraint systems had a 21% reduction in risk for death compared with children in seat belts, although this difference was only marginally significant (RR, 0.79; 95% confidence interval, 0.59-1.05). After excluding the cases of serious child restraint system and seat belt misuse from FARS, children in child restraint systems had a 28% reduction in risk for death compared with children in seat belts (RR, 0.72; 95% confidence interval, 0.54-0.97)." It seems that they are trying to get to that conclusion.
- mcguire 10y ago
  "Further, Table 1 says that seat belts had a non-fatal rate of 99.89% and restraint systems had a non-fatal rate of 99.88%." Um, no, I'm afraid. Table 1 describes the characteristics of the data set. 99.89% of the "seat belt" sample were non-fatal accidents and 0.11% were fatal; that and the row immediately above it sum to 100%. A fatal accident is defined as one in which someone died, including a pedestrian.
  - mhuffman 10y ago
    I am afraid that you are mistaken. You will note that they say: "Within FARS, we identified 7813 children aged 2 through 6 years who were vehicle occupants restrained in a child restraint system or a seat belt in a nondrivable passenger car, van, pickup truck, or sport-utility vehicle that was involved in a crash with at least 1 passenger fatality between 1998 and 2003. Of these 7813 children involved in fatal crashes, 1096 children (14%) were killed." You will then note that in Table 1 for "Overall" the Fatal rate is 1096 (identical to the number of children, the 14% above, that were killed). You will also note that if you add together the FARS and NASS CDS numbers you will get 9246, which is the total number of children aget 2-6 from both and also the sum of 1096 and 8150 from the "Overall" column on Table 1. now that I think about it, it doesn't even matter. If the same relative rates are fatal and non-fatal (separately) that still says that they are practically equivalent. Also, it says so in the paper...
- zrail 10y ago
  The result still seems compelling to me. If I can reduce the risk of my child being killed in a car accident by 28% (even if the raw numbers are small) I'm going to do it. I don't want to change the goal posts here, but death isn't the only thing these booster seats protect against. A properly used booster seat reduces the relative risk of non-fatal injury by more than half[1]. That is also extremely compelling to me. [1]: http://jama.jamanetwork.com/mobile/article.aspx?articleid=196677 http://jama.jamanetwork.com/mobile/article.aspx?articleid=19...
  - mhuffman 10y ago
smileysteve 10y ago
A 4 or 6 point harness for adults and mandatory bolsters would have a major effect on the fatalities too, but would likely result in fewer people wearing them. Hans and helmets would also save us all from airbags.

mcguire 10y ago

The easy-to-read tables match their results: "Results Compared with seat belts, child restraints, when not seriously misused (eg, unattached restraint, child restraint system harness not used, 2 children restrained with 1 seat belt) were associated with a 28% reduction in risk for death (relative risk, 0.72; 95% confidence interval, 0.54-0.97) in children aged 2 through 6 years after adjusting for seating position, vehicle type, model year, driver and passenger ages, and driver survival status. When including cases of serious misuse, the effectiveness estimate was slightly lower (21%) (relative risk, 0.79; 95% confidence interval, 0.59-1.05)."

mhuffman 10y ago
That is their conclusion (which I addressed in my comment). Read the table: Table 1 says that seat belts had a non-fatal rate of 99.89% and restraint systems had a non-fatal rate of 99.88%. They flat-out say that they had to adjust it to get those numbers: "Table 2 summarizes little difference in the unadjusted risk for death between users of child restraint systems and users of seat belts (RR, 1.03; 95% confidence interval, 0.72-1.46). After adjusting for seating position, vehicle type, model year, driver and passenger ages, and driver survival status, children in child restraint systems had a 21% reduction in risk for death compared with children in seat belts, although this difference was only marginally significant (RR, 0.79; 95% confidence interval, 0.59-1.05). After excluding the cases of serious child restraint system and seat belt misuse from FARS, children in child restraint systems had a 28% reduction in risk for death compared with children in seat belts (RR, 0.72; 95% confidence interval, 0.54-0.97)." If you read further down in their conclusions, they seem to have a real hard-on over Levitt. I am not saying that they are wrong, but the data (un-modified) supports Levitt's conclusion.
- mcguire 10y ago
  I presume you mean this: "In a more recent series of analyses, Levitt4 and Dubner and Levitt11 used FARS data from 1975 to 2003 and, by various methods, directly compared the mortality with child restraint systems vs seat belts in children aged 2 to 6 years and could not demonstrate a difference in effectiveness. Levitt and Porter12 restricted the FARS data set to 2-vehicle crashes in which someone in the other vehicle (ie, the vehicle without the index child occupant) died, under the assumption that the distribution of restraint use among children in potentially fatal crashes is independent of whether someone in the other vehicle dies, after adjusting for various crash-related characteristics. "The precision of these previous effectiveness estimates and their relevance to today's fleet were limited by their reliance on FARS (the limits of which were presented in the introduction), by the inclusion of older vehicles and restraints, and by failing to control for the severity (potential unsurvivability) of the crashes. Our analysis based on a modern cohort of children involved in crashes in which the car was rendered undrivable addressed many of the limitations of these previous analyses and found effectiveness estimates for child restraint systems to be greater than that for seat belts alone, with estimates greater than those of both Levitt4 and Hertz.6" Levitt, et al, used only FARS data, which only records fatal accidents. A hypothetical accident where only the child would have died but that was prevented by the restraints would therefore not show up in the data, leading to the value of the restraints being under reported. Further, failing to control for the severity of the accident (which this work does using the survival of the driver) also undervalues restraints: if the car ends up as a ball the size of a grapefruit, it doesn't matter what restraints were used.