Drunkenness Risks – Walking vs Driving: Oops?

To Stephen J Dubner, the Author of “Superfreakonomics”

Dear sir,

Please forgive me writing to you unannounced, but I have just started reading Superfreakonomics and read the early section which analyses the differing risks between drunks walking and driving. You concluded that on a per-mile basis, walkers were eight times more likely to die than drivers.

This seems to me to be an incorrect conclusion because the likelihood of death is a function of time, not distance travelled – the longer you are exposed to a danger the more you are likely to be a victim of it. Walkers travel at around 3 miles per hour, drunken walkers perhaps manage 2. Drunken drivers average (let say) around 40 miles per hour.

So on a per-mile basis, drunken walkers are “out there” and at risk for twenty times longer than drunken drivers.

Combining the two, we have to conclude that on a per-minute basis, drunken drivers are around two and a half times more likely to die than drunken walkers.

Hope this makes sense!

Thanks for an entertaining read, I shall resume my nit-picking now <grin>

Best regards,

Paul Harper

To which I got the reply:

From: “Stephen J. Dubner” <xxxxxx@xxxxxx.xxx>
Date: Sat, 3 Jul 2010 07:20:36 -0400