If You Look Long Enough You Can Find a Pattern in Anything
Which is more dangerous, a gun or a swimming pool?
Consider the parents of an eight-year-old girl named, say, Molly. Her two best friends, Amy and Imani, each live nearby. Molly’s parents know that Amy’s parents keep a gun in their house, so they have forbidden Molly to play there. Instead, Molly spends a lot of time at Imani’s house, which has a swimming pool in the backyard. Molly’s parents feel good about having made such a smart choice to protect their daughter.
But according to the data, their choice isn’t smart at all. In a given year, there is one drowning of a child for every 11,000 residential pools in the United States. (In a country with 6 million pools, this means that roughly 550 children under the age of ten drown each year.) Meanwhile, there is 1 child killed by a gun for every 1 millionplus guns. (In a country with an estimated 200 million guns, this means that roughly 175 children under ten die each year from guns.) The likelihood of death by pool (1 in 11,000) versus death by gun (1 in 1 million-plus) isn’t even close: Molly is roughly 100 times more likely to die in a swimming accident at Imani’s house than in gunplay at Amy’s.
{ Steven D. Levitt & Stephen J. Dubner, Freakonomics, Chapter 5 }
Levitt compares the national ratios of number of pool deaths by children / the number of pools, against the number of children killed by guns / the number of guns, concluding that the likelihood of death by pool is 1 in 11,000 versus death by gun which is 1 in 1 million plus. However, in the hypothetical which precedes this comparison, he notes that “Molly” is forbidden from going to “Amy’s” house. Therefore Molly would be visiting a gun-owning household, not a gun.
I think there are approximately 110 million households in the US, and apparently 2 in 5 households own guns, according to a 2001 Harris Interactive study (the first Google-supplied link that I clicked). That means that there are roughly 44 million gun-owning households. The risk of death by gun for Molly is closer to 1 in 250,000. Still not close to the risk posed by a pool, but much riskier than Levitt concludes. (I do think that it’s safe to assume that there is one pool per household!).
While I don’t have access to the data, it would be interesting to know if the swimming pool / gun comparison would also turn differently depending on the age of the children involved. I.e. do most children swimming pool deaths occur in children under the age of 5? What about gun deaths?
However, a friend of mine pointed out that Levitt’s conclusion may be more seriously misleading. Levitt asserts that conventional instincts of parents are wrong because pools are more dangerous than guns; while it may well be the existence of this conventional wisdom which has led to guns being safer than pools. The perception that one activity is safe and the other unsafe is a self-fulfilling prophecy. Guns kill fewer children because parents are more cognizant of the dangers and act/parent accordingly. The statistics Levitt cites probably merely reflect successful parenting.
Levitt based his analysis on deaths-per-year, but the relevant statistic may be related to exposure rate or, even more importantly for children, to the unsupervised exposure rate.
{ Errors in Freakonomics | Amazon.com review by M. Parker, NY, October 2005 }
images { Andrew Brooke, Gun Tattoo, 1998 | gun tattoo | Watch Around Water ad }
