What is the percentage of a roller coaster falling?

This is an impossible question to answer, as it is too difficult to know how many people ride them every year. There are millions of riders, and perhaps a handful of deaths...most people killed after maintenance workers, not riders. The percentage will be les than 0.000001% if you're using this figure to work out whether you are going to die next time you ride a roller coaster, don't bother. You won't. It's near to impossible.