How the World Really Works: The Science Behind How We Got Here and Where We're Going

by Vaclav Smil

At the opposite end of the voluntary risk spectrum are activities whose brief duration carries a high probability of death. None is riskier than base jumping from cliffs, towers, bridges, and buildings. The most reliable study of this “asking for it” madness looked at an 11-year period of jumping from the Kjerag Massif in Norway, where 1 in every 2,317 jumps (9 in total) resulted in death,[55] with an average exposure risk of 4 × 10-2 (0.04). For comparison, in skydiving a fatal accident used to take place roughly once every 100,000 jumps but the latest US data show one fatality for every 250,000 jumps. With a typical descent lasting five minutes the exposure risk is only about 5 × 10-5, still 50 times higher than just sitting in a chair for those five minutes—but it is only about 1/1,000 of the risk associated with base jumping.[56]