Dissent Of The Day

by Patrick Appel

A reader writes:

While I agree with the broader point (who wouldn’t) Ms. Wallace is making in her post on risk, this business of airplane vs car safety seems to be an often misunderstood notion. the stats in question (link from original post) give the following (2005 figures – dividing fatalities on board by total miles or total departures):

0.0025 deaths per million miles and 0.18 per 100,000 departures

Sounds good, right? Well, yes, but let's compare this to road accidents (ntsb and bureau of transportation statistics):

0.009 deaths per million miles and 0.009 per 100,000 trips (10 miles average trip length)

Air travel and road travel have about the same death rate per mile (air travel seems a little better - factor of 4), but cars win out on a per trip basis by over an order of magnitude (factor of 20). Hence, I'm really not sure that claiming air travel is safer than travel on foot is really justified - it seems very much to be a question of one one slices the data. Moreover, I would argue that the sensible statistic is deaths per trip, in which case road travel is clearer safer. There's probably a broader point that should be made here about the ease with which one can make data tell many different stories when asking imprecise questions, but I should really get back to pretending to work.