I found this little tidbit at mounteverest.net:
Today, Everest has hosted close to 2,000 successful summits. 179 people have perished giving a fatality rate of 9.3% (fatality rate is defined as successful summits compared to fatalities). However, since 1990 there has been an explosion of summiteers and fatality statistics have changed. Up to 1990 the Everest fatality rate is a whopping 37%, yet from 1990 until today the rate has dropped to 4.4%.
This is just a hunch, but I think there would be a number of reasons for the drop in fatilities in the last two decades:
- Advances in lightweight cold weather clothing has made it easier to keep climbers warmer while at the same time making movement easier.
- Advances in communications, especially radio and GPS makes it easier to locate stranded climbers.
- The higher number of people on the mountain and in base camps probably has also resulted in more highly-trained doctors and medical experts capable of treating hypothermia and altitude conditions (especially when you consider how many of the expeditions are sponsored by very wealthy people who have the funds to cover all contingencies).
- The fact that there are more people on the mountain during climbing season (and many of the sherpas are seasoned climbers with multiple full and partial ascents) makes rescues easier and ascents safer.