And did you control for color?

This article turned up in a sidebar in the text of a statistics textbook that I'm recording: Smith and Pell, "Parachute use to prevent death and major trauma related to gravitational challenge: systematic review of randomised controlled trials." I think the conclusion pretty much covers it:

As with many interventions intended to prevent ill health, the effectiveness of parachutes has not been subjected to rigorous evaluation by using randomised controlled trials. 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.