# Seat Belts: Questionable math in news article...

Not sure where to put this, but thought GQ was best…mods, move if necessary.

My daughter is a Hanna Montana fan, so of course I have to read any story concerning the teen phenom. She and her father Billy Ray Cyrus recently caused a tabloid dust-up because they were photographed not wearing seatbelts while riding in the rear seat of a Range Rover. The elder Cyrus has apologized for the gaffe, but this paragraph in the article–quoted from the Us Weekly blog posting about the gaffe–leapt out at me:

I’m having trouble decipering this. 58.2% were not wearing seat belts, 32.7% were buckled up; what then about the remaining 9.1%? I have also heard (anecdotally; don’t have a cite handy) that seat belts reduce your chances of dying in a crash by a factor of 6. So even if I take those numbers comparatively (In any crash with fatalities, 58.2% of unbuckled rear-seat passengers die vs. 32.7% of buckled rear-seat passengers) it just doesn’t seem to match my impression of the safety margin provided by seatbelts.

So can anyone find a better way to understand this, and more broadly, what’s the Straight Dope on buckling up in the rear seat? Of course its a sensible precaution–I can’t imagine anyone arguing otherwise–but just how much protection does it provide?

I don’t have any knowledge of the actual numbers, but you cannot compare only these numbers when making judgments about the safely margin of seatbelts.

For example, if 58.2% of the population did not wear seatbelts and 32.7% did then the statistics above indicate that the seatbelts have no effect on your safety whatsoever.

However if 90% of people do wear seatbelts and only 10% do not then if 58.2% of the fatalities were from the 10% of people who do not wear seatbelts it appears to be a pretty strong argument for seatbelts.

I’m simplifying a lot, but in short this just isn’t enough information for any conclusions about seatbelt safety.

Be careful of your statistics. The numbers as given don’t say very much about how much wearing a seatbelt improves your safety. The original quote said “58.2 percent of all rear seat fatalities involved passengers who were not wearing seat belts, compared to 32.7 percent of fatalities for rear seat passengers who were wearing seat belts.”. I don’t see any mention there of the percentage of passengers overall that wear seatbelts. Consider hypothetically a locale where everybody wears seatbelts all the time. In that locale, 100% of all rear seat fatalities would involve passengers wearing seatbelts and 0% would involve people not wearing seatbelts.

ETA - Looks like Driver8 beat me to the same conclusion!

Sounds like sloppy numbers.

Seat belts won’t matter at very high speed crashes, side impacts, a larger vehicle crushing a smaller one (by driving or rolling over/on top of it), etc.

I wouldn’t be surprised if some of those 33% sealt belt wearing fatalities may have died in circumstances where the seat belt didn’t matter much, anyway.

Did the article give a cite for those numbers?

This would imply that the two cited firgures should total 100%. They don’t, so I’m not sure what the article means.

The overall point is a good one–if a vast majority of people wear seatbelts in the back seat, then 58.2% of rear-seat fatalities occurred in the tiny fraction that didn’t. The apparently high 32.7% comes from the fact that the much larger belted group is going to get the lion’s share of horrific crashes where death comes regardless of whether you’re strapped in. I agree it’s misleading–which is why it shouldn’t be used in a news article.

“According to 2006 data compiled by the National Highway Traffic Safety Administration…”

I looked through the NHTSA website briefly, and couldn’t find the exact numbers quoted, but they did have 3 categories - rear belt used, not used, and unknown, which may account for why the numbers don’t add to 100%. And yes, it’s a fairly useless statistic, but it’s pretty much what I’d expect from a reporter covering the entertainment beat.