It turns out that, as of 2003, no proper double blind study of parachute use has been conducted. That is to say that science doesn't technically have the most firm evidence that parachutes work.
This observation is, of course, made in jest.
Advocates of evidence based medicine have criticised the adoption of interventions evaluated by using only observational data. We think that everyone might benefit if the most radical protagonists of evidence based medicine organised and participated in a double blind, randomised, placebo controlled, crossover trial of the parachute.
One of the people in the photo above is going to have a bad day. I think I shall cite this study more often.