Nitpick from a former partial Everest climber. The ratio of deaths to summit successes used to be about 5% but the majority of climbers, including me, turn around before getting there.

I think the death ratio is down now there are pretty much fixed ropes the whole way to the summit on the south side. The 'Into Thin Air' deaths were because they lost their way in a storm but now you just clip onto the guide rope and walk up/down.

The attempt to death ratio is probably more like 0.5% or 0.2% though there aren't really proper figures on number of attempts.